Earth Science Glossary
(Most definitions taken from Earth Science 11e)
(Last update - July 27, 2008)
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§
0/00 – The
symbol for parts per thousand. §
Aa – A
type of lave flow that has a jagged blocky surface. §
Ablation –
A general term for the loss of ice and snow from a glacier §
Abrasion –
The grinding and scraping of a rock surface by the friction and impact of
rock particles carried by water, wind, or ice. §
Absolute Humidity – The weight of water vapor in a given volume of air (usually
expressed in grams/m3 §
Absolute instability - Air that has a lapse rate greater than the dry
adiabatic rate. §
Absolute magnitude - The apparent brightness of a star if it were viewed
from a distance of 10 parsecs (32.6 light-years). Used to compare the true
brightness of stars. §
Absolute stability - Air with a lapse rate less than the wet adiabatic
rate. §
Absorption Spectrum - A continuous spectrum with dark lines superimposed. §
Abyssal plain - Very level area of the
deep-ocean floor, usually lying at the foot of the continental rise §
Abyssal zone - A subdivision of the benthic
zone characterized by extremely high pressures, low temperatures, low oxygen,
few nutrients, and no sunlight §
Accretionary wedge A large wedge-shaped mass of sediment that accumulates in
subduction zones. Here sediment is scraped from the subducting oceanic plate
and accreted to the overriding crustal block. §
Acid precipitation - Rain or snow with a pH value that is less than the
pH of unpolluted (?) precipitation §
Active continental margin - Usually narrow and consisting of highly deformed
sediments. They occur where oceanic lithosphere is being subducted beneath
the margin of a continent. §
Adiabatic temperature change - Cooling or warming of air caused when air is allowed
to expand or is compressed, not because heat is added or subtracted. Dry air changes at 10°C/1,000m, and wet air (condensation has begun)
changes at 5-9°C/1,000m. §
Advection - Horizontal
convective motion, such as wind. §
Advection fog - A fog formed when warm, moist air is blown over a cool surface. §
Aerosols - Tiny
solid and liquid particles suspended in the atmosphere. §
Aftershocks
- Smaller earthquakes that follow the main
earthquake §
Air - A
mixture of many discrete gases, of which nitrogen and oxygen are most
abundant, in which varying quantities of tiny solid and liquid particles are
suspended. §
Air mass - A
large body of air that is characterized by a sameness of temperature and
humidity. §
Air-mass weather - The conditions experienced in an area as an air
mass passes over it. Because air masses are large and fairly homogenous,
air-mass weather will be fairly constant and may last for several days. §
Air pollutants - Airborne particles and gases
that occur in concentrations that endanger the health and well-being of
organisms or disrupt the orderly functioning of the environment. §
Air pressure - The force exerted by the weight of a column of air above a given
point. §
Albedo - The
reflectivity of a substance, usually expressed as a percentage of the
incident radiation reflected. §
Alluvial fan - A fan-shaped deposit of sediment formed when a stream's slope is
abruptly reduced. §
Alluvium - Unconsolidated sediment deposited by a
stream. §
Alpine glacier - A glacier confined to a mountain valley, which in most instances had
previously been a stream valley. §
Altitude (of the Sun) - The angle of the Sun above the horizon. §
Andesitic composition - See Intermediate
composition. §
Anemometer - An
instrument used to determine wind speed. §
Aneroid barometer - An instrument for measuring air pressure that consists
of evacuated metal chambers very sensitive to variations in air pressure. §
Angle of repose - The steepest angle at which loose material remains stationary without
sliding downslope. §
Angular unconformity - An unconformity in which the strata below dip at an
angle different from that of the beds above. §
Annual mean temperature - An average of the 12 monthly temperature means. §
Annual temperature - The difference between the highest and lowest
monthly temperature means. §
Annual temperature range - §
Antarctic Circle – The parallel of latitude at 66½° S. It is
the furthest latitude away from (north of) the South Pole that will receive
24 hours of Sunlight on the winter solstice (December 21). §
Anthracite - A hard, metamorphic form of coal that burns
clean and hot §
Anticline - A fold in sedimentary strata resembling an
arch §
Anticyclone - A high-pressure center characterized by a clockwise flow of air in the
Northern Hemisphere. §
Aphelion - The
place in the orbit of a planet where the planet is farthest from the Sun. §
Aphotic zone - That
portion of the ocean where there is no sunlight. §
Apparent magnitude - The
brightness of a star when viewed from Earth. §
Aquifer - Rock
or soil through which groundwater moves easily §
Aquitard -
Impermeable
beds that hinder or prevent groundwater movement. §
Archean
eon - The second eon of Precambrian
time, following the Hadean and preceding the Proterozoic. It extends between
3.8 billion and 2.5 billion years before the present. §
Arête - A narrow
knifelike ridge separating two adjacent glaciated valleys. §
Arid - See Desert. §
Arid climate - See Dry climate. §
Arkose - A feldspar-rich sandstone. §
Artesian well
- A well in which the water rises above the
level where it was initially encountered. §
Arctic Circle
- The parallel of
latitude at 66½° N. It is
the furthest latitude away from (south of) the North Pole that will receive
24 hours of Sunlight on the summer solstice (June 21). §
Asteroids - Thousands of
small planet like bodies, ranging in size from a few hundred kilometers to
less than a kilometer, whose orbits lie mainly between those of Mars and
Jupiter. §
Asthenosphere
- A
subdivision of the mantle situated below the lithosphere. This zone of weak
material exists below a depth of about 100 kilometers and in some regions
extends as deep as 700 kilometers. The rock within this zone is easily
deformed. §
Astronomical theory - A
theory of climatic change first developed by the Yugoslavian astronomer
Milankovitch. It is based upon changes in the shape of Earth's orbit,
variations in the obliquity of Earth's axis, and the wobbling of Earth's
axis. §
Astronomical Unit (AU) - Average distance from Earth to the Sun; 1.5 X 108
km, or 93 x 106 miles. §
Astronomy - The scientific
study of the universe; it includes the observation and interpretation of
celestial bodies and phenomena. §
Atmosphere - The
gaseous portion of a planet; the planet's envelope of air. One of the traditional
subdivisions of Earth's physical environment. §
Atmospheric instability – Exists when the environmental lapse rate is
greater than the dry adiabatic rate.
This can occur when the air above is very cold. §
Atoll - A continuous or broken ring of coral reef
surrounding a central lagoon. § Atom - The smallest particle that exists
as an element § Atomic mass unit – A proton or neutron has a mass just slightly more than one atomic mass unit, whereas an electron is only about on two-thousandth of an atomic mass unit. (pg 34 of Earth Science 11e) §
Atomic number
- The
number of protons in the nucleus of an atom §
Atomic weight - The average of the atomic
masses of isotopes for a given element §
Aurora - A
bright display of ever-changing light caused by solar radiation interacting
with the upper atmosphere in the region of the poles. §
Autumnal equinox - The equinox that occurs on
September 21-23 in the Northern Hemisphere and on March 21-22 in the Southern
Hemisphere. §
Backshore - The inner portion
of the shore, lying landward of the high-tide shoreline. It is usually dry,
being affected by waves only during storms. §
Backswamp - A poorly
drained area on a floodplain that results when natural levees are present. §
Bar - Common term
for sand and gravel deposits in a stream channel. §
Barchan dune - A
solitary sand dune shaped like a crescent with its tips pointing downward. §
Barchanoid dune - Dunes
forming scalloped rows of sand oriented at right angles to the wind. This form
is intermediate between isolated barchans and extensive waves of transverse
dunes. §
Barograph - A
recording barometer. §
Barometer - An
instrument that measures atmospheric pressure. §
Barometric tendency - See
Pressure tendency. §
Barred spiral - A
galaxy having straight arms extending from its nucleus. § Barrier island - A
low, elongate ridge of sand that parallels the coast. § Barrier reef – A long, narrow ridge of coral or rock parallel to and relatively near a coastline, separated from the coastline by a lagoon too deep for coral growth. §
Basalt - A
fine-grained igneous rock of mafic composition. §
Basaltic composition - A compositional group of
igneous rocks indicating that the rock contains substantial dark silicate
minerals and calcium-rich plagioclase feldspar. §
Base level - The
level below which a stream cannot erode. §
Basin - A
circular downfolded structure. §
Batholith - A
large mass of igneous rock that formed when magma was emplaced at depth,
crystallized, and subsequently exposed by erosion. §
Bathymetry - The
measurement of ocean depths and the charting of the shape or topography of
the ocean floor. §
Baymouth bar - A sandbar that completely crosses a bay, sealing it off from the
open ocean. §
Beach - An
accumulation of sediment found along the landward margin of the ocean or a
lake. §
Beach drift - The
transport of sediment in a zigzag pattern along a beach caused by the uprush
of water from obliquely breaking waves. §
Beach face - The
wet, sloping surface that extends from the berm to the shoreline. §
Beach nourishment - The
process by which large quantities of sand are added to the beach system to
offset losses caused by wave erosion. §
Bed load - Sediment
that is carried by a stream along the bottom of its channel. §
Benioff zone - Zone
of inclined seismic activity that extends from a trench downward into the
asthenosphere. §
Benthic zone - The
marine life zone that includes any sea bottom surface regardless of
its distance from shore. §
Benthos - The
forms of marine life that live on or in the ocean bottom. §
Bergeron process - A
theory that relates the formation of precipitation to supercooled clouds,
freezing nuclei, and the different saturation levels of ice and liquid water. §
Berm - The
dry, gently sloping zone on the backshore of a beach at the foot of the
coastal cliffs or dunes. §
Big Bang Theory - The
theory that proposes that the universe originated as a single mass, which
subsequently exploded. §
Binary stars - Two
stars revolving around a common center of mass under their mutual
gravitational attraction. §
Biogenous sediment - Seafloor
sediments consisting of material of marine-organic origin. §
Biomass - The
total mass of a defined organism or group of organisms in a particular area
or ecosystem. §
Biosphere - The
totality of life on Earth; the parts of the solid Earth, hydrosphere, and
atmosphere in which living organisms can be found. §
Bituminous - The
most common form of coal, often called soft, black coal. §
Black
dwarf - A final state of
evolution for a star, in which all of its energy sources are exhausted and
it no longer emits radiation. §
Black hole - A massive star that has collapsed to such a
small volume that its gravity prevents the escape of all radiation. §
Blowout
(deflation hollow) - A depression
excavated by the wind in easily eroded deposits. §
Bode's law - A sequence of
numbers that approximates the mean distances of the planets from the Sun. §
Body waves - Seismic waves
that travel through Earth's interior. §
Bowen's reaction
series - A concept proposed by N. L. Bowen that illustrates the relationships
between magma and the minerals crystallizing from it during the formation of
igneous rocks. §
Braided
stream - A stream
consisting of numerous intertwining channels §
Breakwater - A structure
protecting a nearshore area from breaking waves. §
Breccia - A sedimentary rock composed of angular fragments that were
lithified. §
Bright-line
spectrum - The bright lines
produced by an incandescent gas under low pressure. §
Bright
nebula - A cloud of
glowing gas excited by ultraviolet radiation from hot stars. §
Brittle
failure (deformation) - Deformation that
involves the fracturing of rock. Associated with rocks near the surface. §
Cactolith - A quasi-horizontal chonolith composed of anastomosing ductoliths,
whose distal ends curl like a harpolith, thin like a sphenolith, or bulge
discordantly like an akmolith or ethmolith. §
Caldera - A large depression typically caused by collapse or ejection of the
summit area of a volcano. §
Calorie - The amount of heat required to raise the
temperature of one gram of water 1°C. §
alving - Wastage of a
glacier that occurs when large pieces of ice break off into water. §
Capacity - The total amount
of sediment a stream is able to transport §
Carbonate group - Mineral group whose members contain the carbonate ion (CO2-2)
and one or more kinds of positive ions. Calcite is a common example. §
Cassini
division - A wide gap in the ring system of Saturn
between the A ring and the B ring. §
Catastrophism
- The concept that Earth was shaped by
catastrophic events of a short-term nature. §
Cavern - A naturally
formed underground chamber or series of chambers most commonly produced by
solution activity in limestone. §
Celestial sphere
- An imaginary hollow
sphere upon which the ancients believed the stars were hung and carried
around Earth. §
Cenozoic era - A span on the
geologic time scale beginning about 65 million years ago following the
Mesozoic era. §
Cepheid variable
- A star whose brightness
varies periodically because it expands and contracts. A type of pulsating
star. §
CFC’s – Short
for chlorofluorocarbons. These are
the compounds thought to be responsible for depleting the Earth’s ozone
layer. They were used for air
conditioning, cleaning solvents, propellants for aerosol sprays, etc. §
Chemical
sedimentary rock - Sedimentary rock
consisting of material that was precipitated from water by either inorganic
or organic means. §
Chemical weathering - The processes by which the internal structure of a mineral is altered
by the removal and/or addition of elements. §
Chinook - - A wind blowing down the leeward side of a
mountain and warming by compression. §
Chromatic aberration - The property of a lens whereby light of different colors is focused
at different places. §
Chromosphere - The first layer
of the solar atmosphere found directly above the photosphere. §
Cinder cone -
A rather small volcano built primarily of
pyroclastics ejected from a single vent. §
Circle of
illumination - The great circle
that separates daylight from darkness. §
Cirque - An amphitheater-shaped basin at the head of a glaciated valley produced
by frost wedging and plucking. §
Cirrus - One of three basic cloud forms; also one of the three high cloud
types. They are thin, delicate ice-crystal clouds often appearing as
veil-like patches or thin, wispy fibers. §
Clastic rock - A sedimentary rock made of broken fragments of
preexisting rock. §
Cleavage - The tendency
of a mineral to break along planes of weak bonding. §
Climate - A description
of aggregate weather conditions; the sum of all statistical weather
information that helps describe a place or region. §
Climate system - The exchanges of
energy and moisture that occur among the atmosphere, hydrosphere, solid
Earth, biosphere, and cryosphere. §
Climate-feedback
mechanism - Because the
atmosphere is a complex interactive physical system, several different
possible outcomes may result when one of the system's elements is altered.
These various possibilities are called climate feedback mechanisms §
Climatology - The scientific study of climate. §
Closed
system - A system that is self contained with regards
to matter—that is, no matter enters or leaves. §
Cloud - A form of condensation best described as a dense
concentration of suspended water droplets or tiny ice crystals. §
Clouds of vertical development - A cloud that has
its base in the low-height range but extends upward into the middle or high
altitudes. §
Cluster
(star) - A large group of
stars. §
Coarse-grained
texture - An igneous rock
texture in which the crystals are roughly equal in size and large enougl so
that individual minerals can be identified with the unaided eye §
Coast - A strip of land
that extends inland from the coastline as far as ocean-related features can
be found. §
Coastline - The coast's seaward edge. The landward limit of the effect of the
highest storm waves on the shore. §
Col - A pass between mountain valleys where the headwalls of two cirques
intersect. §
Cold front - A front along which a cold air mass thrusts beneath a warmer
air mass. §
Collision-coalescence
process - A theory of raindrop formation in warm clouds (above 0°C) in which
large cloud droplets (giants) collide and join together with
smaller droplets to form a raindrop. Opposite electrical charges may bind the
cloud droplets together. §
Column - A feature found in caves that is formed when
a stalactite and stalagmite join. §
Columnar joints - A pattern of cracks that form
during cooling of molten rock to generate columns that are generally
six-sided. §
Coma - The
fuzzy, gaseous component of a comet's head. §
Comet - A small body that generally revolves about
the Sun in an elongated orbit. §
Competence - A
measure of the largest particle a stream can transport; a factor dependent on
velocity. §
Composite cone - Composite cone A volcano composed
of both lava flows and pyroclastic material. §
Compound - A
substance formed by the chemical combination of two or more elements in definite
proportions and usually having properties different from those of its
constituent elements. §
Condensation - The
change of state from a gas to a liquid. §
Condensation nuclei - Tiny bits of particulate matter
that serve as surfaces on which water vapor condenses. §
Conditional instability - Moist air with a lapse rate
between the dry and wet adiabatic rates. §
Conduction - The
transfer of heat through matter by molecular activity. Energy is transferred
through collisions from one molecule to another. §
Conduit - A
pipe-like opening through which magma moves toward Earth's surface. It
terminates at a surface opening called a vent. §
Cone of depression
- A cone-shaped depression in the water table
immediately surrounding a well. §
Conformable - Layers
of rock that were deposited without interruption. §
Conglomerate - A
sedimentary rock composed of rounded gravel-size particles. §
Constellation - An apparent group of stars
originally named for mythical characters. The sky is presently divided into
88 constellations. §
Contact
metamorphism - Changes in rock caused by the heat from a
nearby magma body. §
Continental (c) air mass - An air mass that forms over land; it
is normally relatively dry. §
Continental drift theory - A theory that originally
proposed that the continents are rafted about. It has essentially been
replaced by the plate tectonics theory. §
Continental margin - That portion
of the seafloor adjacent to the continents. It may include the continental
shelf, continental slope, and continental rise. §
Continental rise - The gently
sloping surface at the base of the continental slope. §
Continental shelf - The gently
sloping submerged portion of the continental margin, extending from the
shoreline to the continental slope. §
Continental slope - The steep gradient that leads
to the deep-ocean floor and marks the seaward edge of the continental shelf. §
Continental volcanic arc - Mountains
formed in part by igneous activity associated with the subduction of oceanic
lithosphere beneath a continent. §
Continuous spectrum - An uninterrupted
band of light emitted by an incandescent solid, liquid, or gas under
pressure. §
Convection - The transfer of heat by the
movement of a mass or substance. It can take place only in fluids. §
Convergence - The
condition that exists when the distribution of winds within a given area
results in a net horizontal inflow of air into the area. Because
convergence at lower levels is associated with an upward movement of air,
areas of convergent winds are regions favorable to cloud formation and
precipitation. §
Convergent plate boundary - A boundary in
which two plates move together, causing one of the slabs of lithosphere to be
consumed into the mantle as it descends beneath on an overriding plate. §
Coral reef - Structure formed in a warm, shallow, sunlit
ocean environment that consists primarily of the calcite-rich remains of
corals as well as the limy secretions of algae and the hard parts of many
other small organisms. § Core - Located beneath the mantle, it is the innermost
layer of Earth. The core is divided into an outer core and an inner core. § Coriolis force (effect) - The deflective force of Earth's rotation on all free-moving objects, including the atmosphere and oceans. Deflection is to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. §
Corona - The
outer, tenuous layer of the solar atmosphere. §
Correlation - Establishing
the equivalence of rocks of similar age in different areas. §
Covalent bond - A chemical bond produced by the
sharing of electrons. §
Crater - The
depression at the summit of a volcano, or that which is produced by a
meteorite impact. §
Creep - The
slow downhill movement of soil and regolith. §
Crevasse - A
deep crack in the brittle surface of a glacier. §
Cross-bedding - Structure in which relatively
thin layers are inclined at an angle to the main bedding. Formed by currents
of wind or water. §
Cross-cutting - A principle of relative dating.
A rock or fault is younger than any rock (or fault) through which it cuts. §
Crust - The
very thin outermost layer of Earth. §
Crystal - An
orderly arrangement of atoms. §
Crystal form - The
external appearance of a mineral as determined by its internal arrangement
of atoms. Crystallization §
Crystallization - The formation and growth of a
crystalline solid from a liquid or gas. §
Crystal settling - During the crystallization of
magma, the earlier-formed minerals are denser than the liquid portion and
settle to the bottom of the magma chamber. §
Cumulus One
of three basic cloud forms; also the name given one of the clouds of vertical
development. Cumulus are billowy individual cloud masses that often have
flat bases.- §
Cup anemometer
- See Anemometer. §
Curie point - The temperature above which a
material loses its magnetization. §
Cutoff - A
short channel segment created when a river erodes through the
narrow neck of land between meanders. §
Cyclone - A low-pressure center characterized by a counterclockwise flow of
air in the Northern Hemisphere. §
Daily mean - The mean temperature for a day that is determined by averaging the
24 hourly readings or, more commonly, by averaging the maximum and minimum
temperatures for a day. §
Daily
temperature range - The difference between
the maximum and minimum temperatures for a day. §
Dark-line
spectrum - See Absorption
spectrum. §
Dark
nebula - A cloud of
interstellar dust that obscures the light of more distant stars and appears
as an opaque curtain. §
Daughter
product - An isotope resulting
from radioactive decay. §
Debris
flow - A relatively
rapid type of mass wasting that involves a flow of soil and regolith
containing a large amount of water. Also called mudflows. §
Declination
(stellar) - The angular distance
north or south of the celestial equator denoting the position of a celestial
body. §
Decompression
melting - Melting that
occurs as rock ascends due to a drop in confining pressure. §
Deep-ocean
basin - The portion of
seafloor that lies between the continental margin and the oceanic ridge system.
This region comprises almost 30 percent of Earth's surface. §
Deep-ocean
trench - See Trench. §
Deep-sea
fan - A cone-shaped
deposit at the base of the continental slope. The sediment is transported to
the fan by turbidity currents that follow submarine canyons. §
Deflation - The lifting and removal of loose material by wind. §
Deformation - General term for the processes of folding, faulting, shearing,
compression, or extension of rocks as the result of various natural forces. §
Delta - An accumulation of sediment formed where a stream enters a lake or
ocean. §
Dendritic pattern - A stream
system that resembles the pattern of a branching tree. §
Density - Mass per unit
volume of a substance, usually expressed as grams per cubic centimeter (g/cm3). §
Deposition - The process by which water vapor is changed directly to a solid
without passing through the liquid state. § Desalination - The removal of
salts and other chemicals from seawater. § Desert - One of the two types of dry climate; the driest of the dry climates. §
Desert
pavement - A layer of coarse
pebbles and gravel created when wind removed the finer material. §
Detrital sedimentary rock - Rock formed from the
accumulation of material that originated and was transported in the form of
solid particles derived from both mechanical and chemical weathering. §
Dew-point
temperature - The temperature
to which air has to be cooled in order to reach saturation. §
Differential
weathering - The variation in
the rate and degree of weathering caused by such factors as mineral makeup,
degree of jointing, and climate. §
Diffused
light - Solar energy
scattered and reflected in the atmosphere that reaches Earth's surface in the
form of diffuse blue light from the sky. §
Dike - A tabular-shaped intrusive igneous feature that cuts through the
surrounding rock. §
Dip-slip
fault - A fault in which
the movement is parallel to the dip of the fault. §
Discharge - The quantity of water in a stream that passes a given point in a
period of time. § Disconformity - A type of
unconformity in which the beds above and below are parallel. § Disseminated deposit – Any economic mineral deposit in which the desired mineral occurs as scattered particles in the rock but in sufficient quantity to make the deposit an ore. §
Dissolved load - That portion of a
stream's load carried in solution. §
Distributary - A section of a stream that leaves the main flow. §
Diurnal tidal pattern - A tidal pattern
exhibiting one high tide and one low tide during a tidal day; a daily tide. §
Divergence - The condition
that exists when the distribution of winds within a given area results in a
net horizontal outflow of air from the region. In divergence at lower levels
the resulting deficit is compensated for by a downward movement of air from
aloft; hence, areas of divergent winds are unfavorable to cloud formation and
precipitation. §
Divergent plate boundary - A region
where the rigid plates are moving apart, typified by the mid-oceanic ridges. §
Divide - An imaginary line that separates the drainage of two streams; often
found along a ridge. §
Dome - A roughly
circular upfolded structure similar to an anticline. §
Doppler
effect - The apparent
change in wavelength of radiation caused by the relative motions of the
source and the observer. §
Doppler
radar - In addition to
the tasks performed by conventional radar, this new generation of weather
radar can detect motion directly and hence greatly improve tornado and severe
storm warnings. §
Drainage
basin - The land area
that contributes
water to a stream § Drawdown - The difference in
height between the bottom of a cone of depression and the original height of
the water table. § Drift - see Glacial drift. §
Drumlin - A streamlined asymmetrical hill composed of
glacial till. The steep side of the hill faces the direction from which the
ice advanced. §
Dry adiabatic rate - The rate of
adiabatic cooling or warming in unsaturated air. The rate of temperature
change is 1°C per 100 meters. §
Dry
climate - A climate in
which yearly precipitation is not as great as the potential loss of water by
evaporation §
Dry-summer
subtropical climate - A climate located
on the west sides of continents between latitudes 300 and 45°. It
is the only humid climate with a strong winter precipitation maximum. §
Ductile
deformation - A type of solid
state flow that produces a change in the size and shape of a
rock body without fracturing. Occurs at depths where temperatures and
confining pressures are high. §
Dune - A hill or ridge of wind-deposited sand. §
Earthflow - The downslope movement of water-saturated, clay-rich sediment. Most
characteristic of humid regions. §
Earthquake - The vibration of Earth produced by the rapid release of energy. §
Earth science - The name for all the sciences
that collectively seek to understand Earth. It includes geology,
oceanography, meteorology, and astronomy. §
Earth
system science - An interdisciplinary
study that seeks to examine Earth as a system composed of numerous
interacting parts or subsystems. §
Ebb
current - The movement of a
tidal current away from the shore. §
Eccentricity - The variation of an ellipse from a circle. §
Echo
sounder - An instrument
used to determine the depth of water by measuring the time interval between
emission of a sound signal and the return of its echo from the bottom. §
Eclipse - The cutting off of the light of one celestial body by another passing
in front of it. §
Ecliptic - The yearly path of the Sun plotted against the background of stars. §
Elastic
rebound - The sudden
release of stored strain in rocks that results in movement along a fault. §
Electromagnetic
radiation - See Radiation. §
Electromagnetic spectrum - The distribution
of electromagnetic radiation by wavelength. § Electron - A negatively charged subatomic particle
that has a negligible mass and is found outside an atom's nucleus. A proton
or neutron has a mass just slightly more than one atomic mass unit, whereas an
electron is only about on two-thousandth of an atomic mass unit. (pg 34,
Earth Science 11e) §
Element - A substance that cannot be decomposed into simpler substances by
ordinary chemical or physical means. §
Elements
of weather and climate - Those quantities
or properties of the atmosphere that are measured regularly and that are
used to express the nature of weather and climate. §
Elliptical
galaxy - A galaxy that is
round or elliptical in outline. It contains little gas and dust, no disk or
spiral arms, and few hot, bright stars. §
El Nino - The name given to
the periodic warming of the ocean that occurs in the central and eastern
Pacific. A major El Nino episode can cause extreme weather in many parts of
the world. §
Eluviation - The washing out of fine soil components from the A horizon by
downward-percolating water §
Emergent
coast - A coast where
land that was formerly below sea level has been exposed either because of
crustal uplift or a drop in sea level or both. §
Emission nebula - A gaseous nebula that derives
its visible light from the fluorescence of ultraviolet light from a star in
or near the nebula. §
End
moraine - A ridge of till
marking a former position of the front of a glacier. §
Energy - The capacity to
do work. §
Energy
levels - Spherically
shaped negatively charged zones that surround the nucleus of an atom. §
Environment - Everything that surrounds and influences an organism. Environmental
lapse rate The rate of temperature decrease with increasing height in the
troposphere. §
Environmental lapse rate – (see also “lapse rate”) The actual
(observed as opposed to calculated) decrease in temperature with an increase
in altitude through the troposphere. §
Eon - The largest
time unit on the geologic time scale, next in order of magnitude above era. §
Ephemeral
stream - A stream that is usually dry because it carries
water only in response to specific episodes of rainfall. Most desert
streams are of this type. §
Epicenter - The location on
Earth's surface that lies directly above the focus of an earthquake. §
Epoch - A unit of the geologic calendar that is a subdivision of a period. §
Equatorial low - A belt of low
pressure lying near the equator and between the subtropical highs. §
Equatorial
system - A method of locating
stellar objects much like the coordinate system used on Earth's surface. §
Equinox - The time when the vertical rays of the Sun
are striking the equator. The length of daylight and darkness is equal at
all latitudes at equinox. §
Era - A major division on the geologic calendar;
eras are divided into shorter units called periods. §
Erosion - The incorporation
and transportation of material by a mobile agent, such as water, wind, or
ice. § Eruptive variable - A star that varies in
brightness. § Escape velocity - The initial velocity
an object needs to escape from the surface of a celestial body. § Esker - Sinuous ridge composed largely of sand and gravel deposited by a stream flowing in a tunnel beneath a glacier near its terminus. §
Estuary - A partially enclosed coastal water body that
is connected to the ocean. Salinity here is measurably reduced by the
freshwater flow of rivers. §
Euphotic zone - The portion of
the photic zone near the surface, where light is bright enough for
photosynthesis to occur. §
Evaporation - The process of converting a liquid to a gas. §
Evaporite - A
sedimentary rock formed of material deposited from solution by evaporation
of the water. §
Evapotranspiration - The combined effect of
evaporation and transpiration. §
Evolution, (Theory of) - A fundamental theory in biology and
paleontology that sets forth the process by which members of a population of
organisms come to differ from their ancestors. Organisms evolve by means of mutations,
natural selection, and genetic factors. Modern species are descended from
related but different species that lived in earlier times. §
Exfoliation
dome - Large,
dome-shaped structure, usually composed of granite, formed by sheeting. §
Exotic stream - A permanent stream that
traverses a desert and has its source in well-watered areas outside the
desert. §
External process - Process such as weathering,
mass wasting or erosion that is powered by the Sun and transforms solid rock
into sediment. §
Extrusive - Igneous
activity that occurs outside the crust. §
Eye - A
zone of scattered clouds and calm averaging about 20 kilometers in diameter
at the center of a hurricane. §
Eyepiece - A
short-focal-length lens used to enlarge the image in a telescope. The lens
nearest the eye. §
Eye wall - The
doughnut-shaped area of intense cumulonimbus development and very strong
winds that surrounds the eye of a hurricane. §
Fall - A
type of movement common to mass-wasting processes that refers to the free
falling of detached individual pieces of any size. §
Fault - A
break in a rock mass along which movement has occurred. §
Fault-block mountain - A mountain formed by the
displacement of rock along a fault. §
Fault creep - Displacement
along a fault that is so slow and gradual that little seismic activity
occurs. §
Fault scarp - A cliff created by movement
along a fault. It represents the exposed surface of the fault prior to
modification by weathering and erosion. §
Felsic - The
group of igneous rocks composed primarily of feldspar and quartz. § Fetch - The distance that the wind has
traveled across the open water. Filaments Dark, thin streaks that appear
across the bright solar disk. § Fine-grained texture – A texture of igneous rocks in which the crystals are too small for individual minerals to be distinguished with the unaided eye. §
Fiord - A
steep-sided inlet of the sea formed when a glacial trough was partially
submerged. §
Fissure eruption - An eruption in which lava is
extruded from narrow fractures or cracks in the crust. §
Flare - A
sudden brightening of an area on the Sun. §
Flood basalts - Flows of basaltic lava that
issue from numerous cracks or fissures and commonly cover extensive areas to
thicknesses of hundreds of meters. §
Flood current - The tidal current associated
with the increase in the height of the tide. §
Floodplain - The
flat, low-lying portion of a stream valley subject to periodic inundation. §
Flow - A
type of movement common to mass-wasting processes in which water-saturated material
moves downslope as a viscous fluid. §
Fluorescence - The
absorption of ultraviolet light, which is reemitted as visible light. §
Focal length - The
distance from the lens to the point where it focuses parallel rays of light. §
Focus (earthquake) - The zone within Earth where
rock displacement produces an earthquake. §
Focus (light) - The point where a lens or
mirror causes light rays to converge §
Fog - A cloud with its base at or
very near Earth's surface. §
Fold - A bent rock layer or series of
layers that were originally horizontal and subsequently deformed. §
Foliated - A texture of metamorphic rocks
that gives the rock a layered appearance. §
Food chain - A
succession of organisms in an ecological community through which food energy
is transferred from producers through herbivores and on to one or more
carnivores. §
Food web - A group of interrelated food
chains. §
Foreshocks - Small
earthquakes that often precede a major earthquake. §
Foreshore - That
portion of the shore lying between the normal high and low water marks; the
intertidal zone. §
Fossil fuel - General
term for any hydrocarbon that may be used as a fuel, including coal, oil,
and natural gas. §
Fossils - The
remains or traces of organisms preserved from the geologic past. §
Fossil succession - Fossil organisms that succeed
one another in a definite and determinable order, and any time period can be
recognized by its fossil content. §
Fracture - Any
break or rupture in rock along which no
appreciable movement has taken place. §
Freezing - The
change of state from a liquid to a solid. § Freezing nuclei
- Solid particles that serve as cores
for the formation of ice crystals. § Fringing reef – A coral reef formed close to the shoreline of an island or continent. Fringing reefs usually have a rough, table-like surface that is exposed during low tide and a steep edge sloping toward the open water. §
Front - The boundary between two
adjoining air masses having contrasting characteristics. §
Frontal fog - Fog formed when rain evaporates
as it falls through a layer of cool air. §
Frontal
wedging - Lifting
of air resulting when cool air acts as a barrier over which warmer, lighter
air will rise. §
Frost wedging - The mechanical breakup of rock
caused by the expansion of freezing water in cracks and crevices. §
Fumarole - A
vent in a volcanic area from which fumes or gases escape. §
Galactic cluster - A system of galaxies containing
from several to thousands of member galaxies. §
Geocentric - The
concept of an Earth-centered universe. §
Geologic time scale - The division of Earth history
into blocks of time—eons, eras, periods, and epochs. The time scale was
created using relative dating principles. §
Geology - The
science that examines Earth, its form and composition, and the changes it has
undergone and is undergoing. §
Geosphere - The
solid Earth, the largest of Earth's four major spheres. §
Geostrophic wind - A wind, usually above a height
of 600 meters (2000 feet), that blows parallel to the isobars. Geothermal
energy Natural steam used for power generation. §
Geothermal gradient - The gradual increase in
temperature with depth in the crust. The average is 30°C per kilometer in
the upper crust. §
Geyser - A
fountain of hot water ejected periodically. §
Giant (star) - A
luminous star of large radius. §
Glacial drift - An all-embracing term for
sediments of glacial origin, no matter how, where, or in what shape they
were deposited. §
Glacial erratic - An ice-transported boulder that
was not derived from bedrock near its present site. §
Glacial striations - Scratches and grooves on
bedrock caused by glacial abrasion. §
Glacial trough - A mountain valley that has been
widened, deepened, and straightened by a glacier. §
Glacier - A
thick mass of ice originating on land from the compaction and
recrystallization of snow that shows evidence of past or present flow. §
Glassy - A
term used to describe the texture of certain igneous rocks, such as obsidian,
that contain no crystals. §
Glaze - A
coating of ice on objects formed when supercooled rain freezes on contact. §
Globular cluster - A nearly spherically shaped
group of densely packed stars. §
Globule - A
dense, dark nebula thought to be the birthplace of stars. §
Gondwanaland - The
southern portion of Pangaea consisting of South America, Africa, Australia,
India, and Antarctica §
Graben - A
valley formed by the downward displacement of a fault‑bounded block. §
Graded bed - A
sediment layer that is characterized by a decrease in sediment size from
bottom to top. §
Gradient - The
slope of a stream; generally measured in feet per mile. §
Granitic composition A
compositional group of igneous rocks that indicates a rock is composed
almost entirely of light-colored silicates. §
Granules - The
fine structure visible on the solar surface caused by convective cells
below. §
Gravitational collapse - The
gradual subsidence of mountains caused by lateral spreading of weak material
located deep within these structures. - §
Greenhouse effect - The
transmission of short-wave solar radiation by the atmosphere, coupled with
the selective absorption of longer-wavelength terrestrial radiation,
especially by water vapor and carbon dioxide. §
Groin - A short wall
built at a right angle to the shore to trap moving sand. §
Ground moraine - An
undulating layer of till deposited as the ice front retreats. §
Groundwater - Water
in the zone of saturation §
Guyot - A
submerged flat-topped seamount. §
Gyre - The
large circular surface current pattern found in each ocean. § Habit –
I think this is geology talk for the crystal shape of a mineral. § Hadean eon - The first eon on the geologic time scale; this eon ended 3.8 billion years ago and preceded the Archean eon. §
Hail - Nearly
spherical ice pellets having concentric layers and formed by the successive
freezing of layers of water. §
Half-life - The
time required for one half of the atoms of a radioactive substance to decay. §
Halocline - A
layer of water in which there is a high rate of change in salinity in the
vertical dimension. §
Hanging valley - A
tributary valley that enters a glacial trough at a considerable height above
its floor. §
Hardness - The
resistance a mineral offers to scratching. §
Hard stabilization - Any
form of artificial structure built to protect a coast or to prevent the
movement of sand along a beach. Examples include groins, jetties,
breakwaters, and seawalls. §
Heliocentric - The
view that the Sun is at the center of the solar system. §
Heat - The
kinetic energy of random molecular motion. §
Hertzsprung-Russell
diagram See H-R
diagram. §
High - A center of
high pressure characterized by anticyclonic winds. §
High cloud - A
cloud that normally has its base above 6000 meters; the base may be lower in
winter and at high-latitude locations. §
Highland climate - Complex
pattern of climate conditions associated with mountains. Highland climates
are characterized by large differences that occur over short distances. §
Hogback - A
narrow, sharp-crested ridge formed by the upturned edge of a steeply dipping
bed of resistant rock. §
Horizon - A
layer in a soil profile. §
Horn - A pyramid-like peak formed by glacial action
in three or more cirques surrounding a mountain summit §
Horst - An
elongate, uplifted block of crust bounded by faults. §
Hot spot - A
concentration of heat in the mantle capable of producing magma, which in turn
extrudes onto Earth's surface. The intraplate volcanism that produced the
Hawaiian Islands is one example. §
Hot spring - A spring in
which the water is 6-9°C (10-15°F) warmer than the mean annual air
temperature of its locality. §
H-R diagram -
A plot of stars according to their absolute magnitudes and spectral types. §
Hubble's law - Relates the distance to a galaxy and its velocity. §
Humid continental climate - A
relatively severe climate characteristic of broad continents in the middle
latitudes between approximately
40 and 50 degrees north latitude. This climate is not found in the Southern Hemisphere,
where the middle latitudes are dominated by the oceans. §
Humidity -
A general term referring to water vapor in the air but not to liquid droplets
of fog, cloud, or rain. §
Humid subtropical climate - A
climate generally located on the eastern side of a continent and
characterized by hot, sultry summers and cool winters. §
Humus - Organic
matter in soil produced by the decomposition of plants and animals. §
Hurricane - A
tropical cyclonic storm having winds in excess of 119 kilometers (74 miles)
per hour. §
Hydrogen burning - The
conversion of hydrogen through fusion to form helium. §
Hydrogenous sediment - Seafloor
sediments consisting of minerals that crystallize from seawater. An important
example is manganese nodules. §
Hydrosphere - The
water portion of our planet; one of the traditional subdivisions of Earth's
physical environment. §
Hydrothermal solution - The
hot, watery solution that escapes from a mass of magma during the later
stages of crystallization. Such solutions may alter the surrounding country
rock and are frequently the source of significant ore deposits. §
Hygrometer - An
instrument designed to measure relative humidity. §
Hygroscopic nuclei - Condensation
nuclei having a high affinity for water, such as salt particles. §
Hypothesis - A tentative
explanation that is tested to determine if it is valid. §
Ice cap - Amass
of glacial ice covering a high upland or plateau and spreading out radially. §
Ice cap climate - A
climate that has no monthly means above freezing and supports no vegetative
cover except in a few scattered high mountain areas. This climate, with its
perpetual ice and snow, is confined largely to the ice sheets of Greenland
and Antarctica. §
Ice sheet - A
very large, thick mass of glacial ice flowing outward in all directions from
one or more accumulation centers. §
Igneous rock - A
rock formed by the crystallization of molten magma. §
Immature soil - A
soil lacking horizons. §
Incised meander - Meandering
channel that flows in a steep, narrow valley. They form either when an area
is uplifted or when base level drops. §
Inclination of the axis - The
tilt of Earth's axis from the perpendicular to the plane of Earth's orbit. §
Inclusion - A
piece of one rock unit contained within another. Inclusions are used in
relative dating. The rock mass adjacent to the one containing the inclusion
must have been there first in order to provide the fragment §
Index fossil - A
fossil that is associated with a particular span of geologic time. §
Inertia - A
property of matter that resists a change in its motion. §
Infiltration - The movement of surface water into rock or soil through cracks and
pore spaces. §
Infrared - Radiation
with a wavelength from 0.7 to 200 micrometers. §
Inner core - The solid
innermost layer of Earth, about 1300 kilometers (800 miles) in radius. §
Inner planets See Terrestrial planets. - §
Inselberg - An
isolated mountain remnant characteristic of the late stage of erosion in an
arid region. §
Intensity (earthquake) - A
measure of the degree of earthquake shaking at a given locale based on the
amount of damage. §
Interface - A
common boundary where different parts of a system interact (ES11e, pg 23). §
Interior drainage - A
discontinuous pattern of intermittent streams that do not flow to the ocean. §
Intermediate composition - The
composition of igneous rocks lying between felsic and mafic. §
Interstellar
matter - Dust and gases found between
stars. §
Intertidal zone - The area where land and sea meet and overlap; the zone between high
and low tides. §
Intraplate volcanism - Igneous
activity that occurs within a tectonic plate away from plate boundaries. §
Intrusive rock - Igneous
rock that formed below Earth's surface. §
Ion - An
atom or molecule that possesses an electrical charge. §
Ionic bond - A
chemical bond between two oppositely charged ions formed by the transfer of
valence electrons from one atom to the other. §
Ionosphere - A
complex zone of ionized gases that coincides with the lower portion of the
thermosphere. §
Iron meteorite - One
of the three main categories of meteorites. This group is composed largely of
iron with varying amounts of nickel (5-20 percent). Most meteorite finds are
irons. §
Irregular galaxy - A galaxy that lacks symmetry §
Island arc See Volcanic island arc. - §
Isobar - A
line drawn on a map connecting points of equal atmospheric pressure, usually
corrected to sea level. §
Isostacy - The
concept that Earth's crust is floating in gravitational balance upon the
material of the mantle §
Isotherms - Lines
connecting points of equal temperature. §
Isotopes - Varieties
of the same element that have different mass numbers; their nuclei contain
the same number of protons but different numbers of neutrons. §
Jet stream - Swift
(120--240 kilometers per hour), high-altitude winds. §
Jetties - A
pair of structures extending into the ocean at the entrance to a harbor or
river that are built for the purpose of protecting against storm waves and
sediment deposition. §
Joint - A
fracture in rock along which there has been no movement. §
Jovian planet - The Jupiter-like planets: Jupiter, Saturn, Uranus, and Neptune.
These planets have relatively low densities. §
Kame - A
steep-sided hill composed of sand and gravel originating when sediment is
collected in openings in stagnant glacial ice. §
Karst - A
topography consisting of numerous depressions called sinkholes §
Kettle holes - Depressions
created when blocks of ice became lodged in glacial deposits and subsequently
melted. §
Koppen classification - A system for classifying
climates devised by Wladimir Koppen that is based on mean monthly and annual
values of temperature and precipitation. §
Kuiper belt - A
region outside the orbit of Neptune where most short-period comets are
thought to originate. §
Laccolith - A massive
igneous body intruded between preexisting strata. §
lahar - Mud
flows on the slopes of volcanoes that result when unstable layers of ash
and debris become saturated §
Lake-effect snow - Snow showers
associated with a cP air mass to which moisture and heat ate added from below
as the air mass traverses a large and relatively warm lake (such as on of the
Great Lakes), rendering the air mass humid and unstable. §
Laminar flow - The movement of water particles in straight-line paths that are
parallel to the channel. The water particles move downstream without mixing. §
Land breeze
- A local wind blowing from land toward the water during the night in coastal
areas. §
La Niña -
An episode of strong trade winds and unusually low sea-surface temperatures
in the central and eastern Pacific. The opposite of El Nino. §
Lapse rate (normal - The average drop in temperature (6.5°C per kilometer;
3.5°F per 1000 feet) with increased altitude in the troposphere. §
Latent heat -
The energy absorbed or released during a change in state. §
Lateral maraine - A ridge of till along the sides of an alpine glacier composed
primarily of debris that fell to the glacier from the valley walls. §
Laurasia - The
northern portion of Pangaea consisting of North America and Eurasia. §
Lava - Magma
that reaches Earth's surface. §
Law of conservation of angular momentum - The product
of the velocity of an object around a center of rotation (axis), and the
distance squared of the object from the axis is constant. §
Leaching - The
depletion of soluble materials from the upper soil by downward-percolating
water. §
Lightning - A
sudden flash of light generated by the flow of electrons between oppositely
charged parts of a cumulonimbus cloud or between the cloud and the ground. §
Light-year - The
distance light travels in a year; about 6 trillion miles. §
Liquefaction - A phenomenon, sometimes associated with earthquakes, in which soils
and other unconsolidated materials containing abundant water are turned into
a fluid-like mass that is not capable of supporting buildings. §
Lithification - The process, generally cementation and/or compaction, of converting
sediments to solid rock. §
Lithosphere - The rigid outer layer of Earth, including the crust and upper mantle. §
Local group - The cluster of 20 or so galaxies to which our galaxy belongs. §
Localized convective lifting - Unequal surface heating that causes localized
pockets of air (thermals) to rise because of their buoyancy. §
Loess - Deposits
of windblown silt, lacking visible layers, generally buff-colored, and
capable of maintaining a nearly vertical cliff. §
Longitudinal (seif dunes) - Long ridges of sand oriented parallel to the
prevailing wind; these dunes form where sand supplies are limited. §
Longshore current - A near-shore
current that flows parallel to the shore §
Low - A
center of low pressure characterized by cyclonic winds. §
Low cloud - A
cloud that forms below a height of 2000 meters. §
Lower mantle - The part of the mantle that extends from the core-mantle boundary to
a depth of 660 kilometers. §
Low-velocity zone - See Asthenosphere. §
Luminosity - The
brightness of a star. The amount of energy radiated by a star. §
Lunar breccia - A lunar rock formed when angular fragments and dust are welded
together by the heat generated by the impact of a meteoroid. §
Lunar eclipse - An eclipse of the Moon. §
Lunar highlands - See Terrae. §
Lunar regolith - A thin, gray layer on the
surface of the Moon, consisting of loosely compacted, fragmented material
believed to have been formed by repeated meteoritic impacts. §
Luster - The
appearance or quality of light reflected from the surface of a mineral. §
Mafic - Igneous
rocks with a low silica content and a high iron-magnesium content. §
Magma - A body of molten rock found at depth,
including any dissolved gases and crystals. §
Magmatic differentiation - The process of generating more than one rock type
from a single magma. §
Magnitude (earthquake) - The total amount of energy released during an
earthquake. §
Magnitude (stellar) - A number given to a celestial object to express its
relative brightness. §
Main sequence - A sequence of stars on the Hertzsprung-Russell diagram, containing
the majority of stars, that runs diagonally from the upper left to the lower
right. §
Maganese nodules - Rounded lumps
of hydrogenous sediment scattered on the ocean floor, consisting mainly of
manganese and iron and usually containing small amounts of copper, nickel,
and cobalt. §
Mantle - The
2900-kilometer (1800mile)-thick layer of Earth located below the crust. §
Mantle convection - is the slow creeping motion of
Earth's rocky mantle in response to perpetual
gravitationally unstable variations in its density. This is likely caused by
differential heating of mantle material by the core. §
Mantle plume - A mass of hotter-than-normal mantle material that ascends toward
the surface, where it may lead to igneous activity. These plumes of solid yet
mobile material may originate as deep as the core-mantle boundary. §
Maria - The
Latin name for the smooth areas of the Moon formerly thought to be seas. §
Marine terrace - A wave-cut platform that has
been exposed above sea level. §
Marine west coast climate - A climate
found on windward coasts from latitudes 40 to 65 degrees and dominated by
maritime air masses. Winters are mild, and summers are cool. §
Maritime (m) air mass - An air mass
that originates over the ocean. These air masses are relatively humid. §
Mass number - The number of neutrons and protons in the nucleus of an atom. §
Mass wasting - The downslope movement of rock, regolith, and soil under the direct
influence of gravity. §
Meander -
A loop-like bend in the course of a stream. §
§
Mean solar day - The average time between two passages of the Sun across the local
celestial meridian. §
Mechanical weathering - The physical disintegration of rock, resulting in
smaller fragments. §
Medial moraine - A
ridge of till formed when lateral moraines from two coalescing alpine
glaciers join. §
Melt - The liquid portion
of magma, excluding the solid crystals. §
Melting - The change of
state from a solid to a liquid. §
Mercalli intensity scale See Modified
Mercalli intensity scale. §
Mercury barometer - A
mercury-filled glass tube in which the height of the mercury column is a
measure of air pressure. §
Mesocyclone - An intense,
rotating wind system in the lower part of a thunderstorm that precedes
tornado development. §
Mesopause - The
boundary between the mesosphere and the thermosphere. §
Mesosphere - The
layer of the atmosphere immediately above the stratosphere and
characterized by decreasing temperatures with height. §
Mesozoic era - A span on the geologic time scale between the Paleozoic and Cenozoic
eras from about 248 million to 65 million years ago. §
Metamorphic rock - Rocks
formed by the alteration of preexisting rock deep within Earth (but still in
the solid state) by heat, pressure, and/or chemically active fluids. §
Metamorphism - The changes in
mineral composition and texture of a rock subjected to high temperature and
pressure within Earth. §
Meteor - The luminous
phenomenon observed when a meteoroid enters Earth's atmosphere and burns up;
popularly called a "shooting star." §
Meteorite - Any
portion of a meteoroid that survives its traverse through Earth's atmosphere
and strikes Earth's surface §
Meteoroid - Small
solid particles that have orbits in the solar system. §
Meteorology - The scientific
study of the atmosphere and atmospheric phenomena; the study of weather and
climate. §
Meteor shower - Many
meteors appearing in the sky caused when Earth intercepts a swarm of
meteoritic particles. §
Middle cloud - A cloud
occupying the height range from 2000 to 6000 meters. §
Middle-latitude cyclone - Large
center of low pressure with an associated cold front and often a warm front.
Frequently accompanied by abundant precipitation. §
Mid-ocean ridge See Oceanic ridge. §
Mineral - A naturally
occurring, inorganic crystalline material with a unique chemical composition. §
Mineralogy - The study of
minerals. §
Mineral resource - All
discovered and undiscovered deposits of a useful mineral that can be
extracted now or at some time in the future. §
Mixed tidal pattern - A
tidal pattern exhibiting two high tides and two low tides per tidal day with
a large inequality in high water heights, low water heights, or both.
Coastal locations that experience such a tidal pattern may also show
alternating periods of diurnal and semidiurnal tidal patterns. Also called
mixed semidiurnal. §
Mixing depth - The
height to which convectional movements extend above Earth's surface. The
greater the mixing depth, the better the air quality. §
Mixing ratio - The
mass of water vapor in a unit mass of dry air; commonly expressed as grams
of water vapor per kilogram of dry air. §
Model - A
term often used synonymously with hypothesis but is less precise because it
is sometimes used to describe a theory as well. §
Modified - Mercalli
intensity scale A 12-point scale developed to evaluate earthquake intensity
based on the amount of damage to various structures. §
Mohorovicic discontinuity (Moho) - The boundary separating the
crust from the mantle, discernible by an increase in seismic velocity. §
Mohs scale - A
series of 10 minerals used as a standard in determining hardness. §
Moment magnitude - A more precise measure of
earthquake magnitude than the Richter scale that is derived from the amount
of displacement that occurs along a fault zone. §
Monocline - A
one-limbed flexure in strata. The strata are unusually flat-lying or very
gently dipping on both sides of the monocline. §
Monsoon - Seasonal
reversal of wind direction associated with large continents, especially
Asia. In winter, the wind blows from land to sea; in summer, from sea to
land. §
Monthly mean temperature - The
mean temperature for a month that is calculated by averaging the daily means. §
Mountain breeze - The
nightly downslope winds commonly encountered in mountain valleys. §
Natural leeves - The
elevated land-forms that parallel some streams and act to confine their
waters, except during floodstage. §
Neap tide - Lowest
tidal range, occurring near the times of the first- and third-quarter phases
of the Moon. §
Nearshore zone - The zone of beach that extends
from the low-tide shoreline seaward to where waves break at low tide. §
Nebula - A cloud of
interstellar gas and/or dust. §
Nebular hypothesis - The basic
idea that the Sun and planets formed from the same cloud of gas and dust in
interstellar space. §
Nekton - Pelagic
organisms that can move independently of ocean currents by swimming or other
means of propulsion. §
Negative feedback mechanism - A feedback mechanism that tends
to maintain a system as it is—that is, maintain the status quo. §
Neritic zone - The marine-life
zone that extends from the low tideline out to the shelf break. §
Neutron - A subatomic
particle found in the nucleus of an atom. The neutron is electrically neutral
and has a mass approximately that of a proton. §
Neutron star - A star of
extremely high density composed entirely of neutrons. §
Nonconformity - An unconformity in which older metamorphic or intrusive igneous rocks
are overlain by younger sedimentary strata. §
Nonfoliated - Metamorphic
rocks that do not exhibit foliation. §
Nonmetallic mineral resource - Mineral
resource that is not a fuel or processed for the metals it contains §
Nonrenewable
resource - Resource that forms or accumulates over such long time spans that
it must be considered as fixed in total quantity §
Normal fault - A fault in which the rock
above the fault plane has moved down relative to the rock below §
Normal polarity - A magnetic field that is the
same as that which exists at present. §
Nova - A
star that explosively increases in brightness. §
Nucleus - The
small heavy core of an atom that contains all of its positive charge and most
of its mass. §
Nuee ardente - Incandescent
volcanic debris buoyed up by hot gases that moves downslope in an
avalanche fashion. § Numerical age
dating - establishing
the approximate age in years
of a particular layer of rock by analyzing the decay of radioactive elements. § Numerical date - Date that specifies the actual number of years that have passed since an event occurred. §
Objective lens - In a refracting telescope, the
long-focal-length lens that forms an image of the object viewed. The lens
closest to the object. §
Obliquity - The angle between the planes of Earth's
equator and orbit. §
Obsidian - A volcanic glass of felsic composition. §
Occluded front - A front formed when a cold
front overtakes a warm front. It marks the beginning of the end of a
middle-latitude cyclone. §
Occlusion - The
overtaking of one front by another. §
Occultation - An
eclipse of a star or planet by the Moon or a planet. §
Ocean basinfloor - Area of the deep-ocean floor
between the continental margin and the mid-ocean ridge. §
Oceanic plateau - An extensive region on the
ocean floor composed of thick accumulations of pillow basalts and other mafic
rocks that in some cases exceed 30 kilometers in thickness. §
Oceanic ridge - A continuous elevated zone on
the floor of all the major ocean basins and varying in width from 500 to 5000
kilometers (300 to 3000 mites). The rifts at the crests of ridges represent
divergent plate boundaries. §
Oceanic zone - The
marine-life zone beyond the continental shelf. §
Oceanography - The
scientific study of the oceans and oceanic phenomena. §
Offshore zone - The relatively flat submerged
zone that extends from the breaker line to the edge of the continental
shelf. §
Oort cloud - A
spherical shell composed of comets that orbit the Sun at distances generally
greater than 10,000 times the Earth-Sun distance. §
Open cluster - A
loosely formed group of stars of similar origin §
Open system - One
in which both matter and energy flow into and out of the system. Most natural
systems are of this type. §
Orbit - The
path of a body in revolution around a center of mass. §
Ore - Usually
a useful metallic mineral that can be mined at a profit. The term is also
applied to certain nonmetallic minerals such as fluorite and sulfur. §
Original horizontality - Layers of sediments are
generally deposited in a horizontal or nearly horizontal position. §
Orogenesis - The processes
that collectively result in the formation of mountains. §
Orographic lifting - Mountains acting as barriers to
the flow of air, forcing the air to ascend. The air cools adiabatically and
clouds and precipitation may result. §
Outer core - A
layer beneath the mantle about 2200 kilometers (1364 miles) thick that has
the properties of a liquid. §
Outer planets See Jovian planets. §
Outgassing - The escape of
gases that had been dissolved in magma. §
Outwash plain - A relatively flat, gently
sloping plain consisting of materials deposited by meltwater streams in
front of the margin of an ice sheet. §
Overrunning - Warm air gliding
up a retreating cold air mass. §
Oxbow lake - A curved lake
produced when a stream cuts off a meander. § Oxide - an oxide is a chemical compound containing at least one oxygen
atom and other elements. Most of the earth's crust consists of oxides. Oxides
result when elements are oxidized by oxygen in the air. § Ozone - A molecule of oxygen containing three oxygen atoms. §
Pahoehoe - A lava flow
with a smooth-to-ropey surface. §
Paleomagnetism - The natural remnant magnetism in
rock bodies. The permanent magnetization acquired by rock that can be used to
determine the location of the magnetic poles and the latitude of the rock at
the time it became magnetized. §
Paleontology - The systematic
study of fossils and the history of life on Earth. §
Paleozoic era - A span
on the geologic time scale between the eons of the Precambrian and Mesozoic
era from about 540 million to 248 million years ago. §
Pangaea - The
proposed supercontinent that 200 million years ago began to break apart and
form the present landmasses. §
Parabolic dunes - The
shape of these dunes resembles barchans, except their tips point into the
wind; they often form along coasts that have strong on‑shore winds,
abundant sand, and vegetation that partly covers the sand. §
Paradigm - A theory that
is held with a very high degree of confidence and is comprehensive in scope. §
Parallax - The apparent
shift of an object when viewed from two different locations. §
Parasitic cone - A volcanic cone that forms on the flank of a larger volcano. §
Parcel - An
imaginary volume of air enclosed in a thin elastic cover. Typically it is
considered to be a few hundred cubic meters in volume and is assumed to act
independently of the surrounding air. § Parent isotope
- An element
that undergoes nuclear decay.
§ Parent material - The material upon which a soil develops. § Parent rock –
when discussing a rock that has undergone change, the parent rock is the rock
that existed before change took place, or from where the current rock was
transported. § Parsec - The
distance at which an object would have a parallax angle of 1 second of arc
(3.26 light-years). §
Partial melting - The
process by which most igneous rocks melt. Since individual minerals have
different melting points, most igneous rocks melt over a temperature range of
a few hundred degrees. If the liquid is squeezed out after some melting has
occurred, a melt with a higher silica content results. §
Passive continental margin - Margins
that consist of a continental shelf, continental slope, and continental
rise. They are not associated with plate boundaries and therefore
experience little volcanism and few earthquakes. §
Pegmatite - A very
coarse-grained igneous rock (typically granite) commonly found as a dike
associated with a large mass of plutonic rock that has smaller crystals.
Crystallization in a water-rich environment is believed to be responsible
for the very large crystals. §
Pelagic zone - Open ocean of any
depth. Animals in this zone swim or float freely. §
Penumbra - The portion of
a shadow from which only part of the light source is blocked by an opaque
body. §
Perched water table - A
localized zone of saturation above the main water table created by an
impermeable layer (aquiclude). §
Peridotite - An igneous
rock of ultramafic composition thought to be abundant in the upper mantle. §
Perihelion - The point in
the orbit of a planet where it is closest to the Sun. §
Period - A basic unit
of the geologic calendar that is a subdivision of an era. Periods may be
divided into smaller units called epochs. §
Periodic table - The
tabular arrangement of the elements according to atomic number. §
Permeability - A
measure of a material's ability to transmit water §
Perturbation - The
gravitational disturbance of the orbit of one celestial body by another, §
Phanerozoic eon - That
part of geologic time represented by rocks containing abundant fossil
evidence. The eon extending from the end of the Proterozoic eon (about 540
million years ago) to the present. §
Phases of the Moon - The
progression of changes in the Moon's appearance during the month. §
Pheoncryst - Conspicuously
large crystals embedded in a matrix of finer-grained crystals. §
Photic zone - The upper part of the ocean into which any sunlight penetrates. §
Photochemical reaction - A chemical reaction in the atmosphere that is triggered
by sunlight, often yielding a secondary pollutant. §
Photon - A discrete
amount (quantum) of electromagnetic energy. §
Photosphere - The region of
the Sun that radiates energy to space. The visible surface of the Sum. §
Photosynthesis - The
process by which plants and algae produce carbohydrates from carbon dioxide
and water in the presence of chlorophyll, using light energy and releasing
oxygen. §
pH scale - A
common measure of the degree of acidity or alkalinity of a solution, it is a
logarithmic scale ranging from 0 to 14. A value of 7 denotes a neutral
solution, values below 7 indicate greater acidity, and numbers above 7
indicate greater alkalinity §
Physical environment - The part of the environment
that encompasses water, air, soil, and rock, as well as conditions such as
temperature, humidity, and sunlight. §
Phytoplankton - Algal
plankton, which are the most important community of primary producers in the
ocean. §
Piedmont glacier - A
glacier that forms when one or more valley glaciers emerge from
the confining walls of mountain valleys and spread out to create a broad
sheet in the lowlands at the base of the mountains. §
Pipe - A vertical
conduit through which magmatic materials have passed. §
Placer - Deposit
formed when heavy minerals are mechanically concentrated by currents, most
commonly streams and waves. Placers are sources of gold, tin, platinum,
diamonds, and other valuable minerals. §
Plane of the ecliptic - The imaginary plane that connects Earth's orbit with
the celestial sphere. §
Planetary nebula - A
shell of incandescent gas expanding from a star. §
Plankton - Passively
drifting or weakly swimming organisms that cannot move independently of ocean
currents. Includes microscopic algae, protozoa, jellyfish, and larval forms
of many animals. §
Plate - One of numerous
rigid sections of the lithosphere that moves as a unit over the material of
the asthenosphere. §
Plate tectonics - The
theory that proposes that Earth's outer shell consists of individual plates
that interact in various ways and thereby produce earthquakes, volcanoes,
mountains, and the crust itself. §
Playa - A flat area
on the floor of an undrained desert basin. Following heavy rain, the playa
becomes a lake. §
Playa lake - A temporary
lake in a playa. §
Pleistocene epoch - An
epoch of the Quaternary period beginning about 1.8 million years ago and
ending about 10,000 years ago. Best known as a time of extensive continental
glaciations. §
Plucking (quarrying) - The process by which pieces of
bedrock are lifted out of place by a glacier. §
Pluton - A structure
that results from the emplacement and crystallization of magma beneath the
surface of Earth. §
Pluvial lake - A
lake formed during a period of increased rainfall. During the Pleistocene
epoch this occurred in some nonglaciated regions during periods of ice
advance elsewhere. §
Polar (P) air mass - A cold air
mass that forms in a high-latitude source region. §
Polar easterlies - In the global
pattern of prevailing winds, winds that blow from the polar high toward the
subpolar low. These winds, however, should not be thought of as persistent
winds, such as the trade winds. §
Polar front - The stormy frontal zone separating air masses of polar
origin from air masses of tropical origin. §
Polar high - Anticyclones that
are assumed to occupy the inner polar regions and are believed to be
thermally induced, at least in part. §
Polar wandering - As
the result of paleomagnetic studies in the 1950s, researchers proposed that
either the magnetic poles migrated greatly through time or the continents had
gradually shifted their positions. §
Population I - Stars rich
in atoms heavier than helium. Nearly always relatively young stars found in
the disk of the galaxy. §
Population II - Stars
poor in atoms heavier than helium. Nearly always relatively old
stars found in the halo, globular clusters, or nuclear bulge. §
Porosity - The volume of
open spaces in rock or soil. §
Porphyritic - An igneous
texture consisting of large crystals embedded in a matrix of much smaller crystals.
Positive feedback mechanism A feedback mechanism that enhances or drives
change. §
Precambrian - All
geologic time prior to the Paleozoic era. §
Precession - A slow motion of Earth's axis that traces
out a cone over a period of 26,000 years. §
Precipitation fog - Fog
formed when rain evaporates as it falls through a layer of cool air. § Pressure – is
the force per unit area applied on a surface in a direction perpendicular to
that surface. (from Wikipedia free
encyclopedia) § Pressure gradient - The amount of pressure change occurring over a given distance. §
Pressure tendency - The
nature of the change in atmospheric pressure over the past several hours. It
can be a useful aid in short-range weather prediction. §
Prevailing wind - A wind
that consistently blows from one direction more than from another. §
Primary pollutants - Those
pollutants emitted directly from identifiable sources. §
Primary productivity - The
amount of organic matter synthesized by organisms from inorganic substances
through photosynthesis or chemosynthesis within a given volume of water or
habitat in a unit of time. §
Primary (P=') wave - A type
of seismic wave that involves alternating compression and expansion of the
material through which it passes. §
Principal shells See Energy levels. - §
Prominence - A
concentration of material above the solar surface that appears as a bright
archlike structure. §
Proterozoic eon - The
eon following the Archean and preceding the Phanerozoic. It extends between
about 2500 million (2.5 billion) and 540 million years ago §
Proton-proton chain - A
chain of thermonuclear reactions by which nuclei of hydrogen are built up
into nuclei of helium. §
Protostar - A collapsing
cloud of gas and dust destined to become a star. §
Psychrometer - A device consisting
of two thermometers (wet bulb and dry bulb) that is rapidly whirled and, with
the use of tables, yields the relative humidity and dew point. §
Ptolemaic system - An Earth-centered system of the
universe. §
Pulsar - A variable
radio source of small size that emits radio pulses in very regular periods. §
Pulsating variable - A
variable star that pulsates in size and luminosity. §
Pycnocline - A layer of
water in which there is a rapid change of density with depth. §
Pyroclastic - An igneous rock texture resulting from the consolidation of individual
rock fragments that are ejected during a violent eruption. §
Pyroclastic flow - A
highly heated mixture, largely of ash and porn ice fragments, traveling down
the flanks of a volcano or along the surface of the ground. §
Pyroclastic material - The volcanic rock ejected during an eruption, including
ash, bombs, and blocks. §
Radial pattern - A system of streams running in all directions away from a central
elevated structure, such as a volcano. §
Radiation - The transfer of energy (heat) through space
by electromagnetic waves §
Radiation fog - Fog
resulting from radiation heat loss by Earth. §
Radiation pressure - The force exerted by electromagnetic radiation from
an object such as the Sun. §
Radioactivity - The
spontaneous decay of certain unstable atomic nuclei. Radiocarbon (carbon-14)
The radioactive isotope of carbon, which is produced continuously in the
atmosphere and is used in dating events from the very recent geologic
past (the last few tens of thousands of years). §
Radio interferometer - Two
or more radio telescopes that combine their signals to achieve the resolving
power of a larger telescope. §
Radiornotric dating - The
procedure of calculating the absolute ages of rocks and minerals that contain
radioactive isotopes. §
Radio telescope - A
telescope designed to make observations in radio wavelengths. § Raindrop – has
a volume equal to roughly 1 million cloud droplets (Earth Science 11e pg
491). § Rainshadow desert - A dry area on the lee side of a mountain range. Many middle-latitude deserts are of this type. §
Rapids - A part of a
stream channel in which the water suddenly begins flowing more swiftly and
turbulently because of an abrupt steepening of the gradient. §
Ray (lunar) - Any of a system
of bright elongated streaks, sometimes associated with a crater on the Moon. §
Recessional moraine - An
end moraine formed as the ice front stagnated during glacial retreat. § Recorded
History – started about
5,000 years ago (pg 586 Earth Science 11e). § Rectangular pattern - A drainage pattern characterized by numerous right-angle bends that develops on jointed or fractured bedrock. § Red giant - A
large, cool star of high luminosity; a star occupying the upper-right portion
of the Hertzsprung-Russell diagram. § Reef – A strip or ridge of rocks, sand, or coral that rises to or near the surface of a body of water §
Reflecting telescope - A telescope that concentrates
light from distant objects by using a concave mirror. §
Reflection - The process
whereby light bounces hack from an object at the same angle at which it
encounters a surface and with the same intensity. §
Reflection nebula - A relatively dense dust cloud in interstellar space
that is illuminated by starlight. §
Refracting telescope - A
telescope that employs a lens to bend and concentrate the light from distant
objects. §
Refraction - The process by
which the portion of a wave in shallow water slows, causing the wave to bend
and tend to align itself with the underwater contours. §
Regional metamorphism - Metamorphism
associated with large-scale mountain-building processes. §
Regolith - The layer of
rock and mineral fragments that nearly everywhere covers Earth's surface. §
Relative dating - Rocks
are placed in their proper sequence or order. Only the chronological order of
events is determined. §
Relative humidity - The
ratio of the air's water-vapor content to its water-vapor capacity. §
Renewable resource - A resource that is virtually inexhaustible or that
can be replenished over relatively short time spans. §
Reserve - Already
identified deposits from which minerals can be extracted profitably. §
Residual soil - Soil
developed directly from the weathering of the bedrock below. §
Resolving power - The
ability of a telescope to separate objects that would otherwise appear as
one. §
Retrograde motion - The
apparent westward motion of the planets with respect to the stars. §
Reverse fault - A fault in which the material above the fault plane moves up in relation
to the material below. §
Reverse polarity - A magnetic field opposite to
that which exists at present. §
Revolution - The motion of
one body about another, as Earth about the Sun. Richter scale A scale of
earthquake magnitude based on the motion of a seismograph. §
Richter scale - §
Ridge push - A
mechanism that may contribute to plate motion. It involves the oceanic
lithosphere sliding down the oceanic ridge under the pull of gravity. §
Rift zone - A
region of Earth's crust along which divergence is taking place. § Right
ascension - An angular
distance measured eastward along the celestial equator from the vernal
equinox. Used with declination in a coordinate system to describe the
position of celestial bodies. § Rime - A thin coating of ice on objects produced when supercooled fog droplets freeze on contact. §
Rock - A
consolidated mixture of minerals. §
Rock cycle - A model that
illustrates the origin of the three basic rock types and the interrelatedness
of Earth materials and processes. §
Rock flour - Ground-up
rock produced by the grinding effect of a glacier. §
Rockslide - The rapid slide
of a mass of rock downslope along planes of weakness. §
Rotation - The spinning of
a body, such as Earth, about its axis. §
Runoff - Water that
flows over the land rather than infiltrating into the ground. §
Salinity - The
proportion of dissolved salts to pure water, usually expressed in parts per
thousand (%o). §
Saltation
- Transportation
of sediment through a series of leaps or bounces. §
Santa Ana - The local name
given a chinook wind in southern California. §
Saturation - The maximum
quantity of water vapor that the air can hold at any given temperature and
pressure. §
Scattering - The redirecting
(in all directions) of light by small particles and gas molecules in the atmosphere.
The result is diffused light. § Scoria - Hardened
lava that has retained the vesicles produced by escaping gases. Scoria cone See
Cinder cone. § Sea – that salt waters that cover the greater part of the earth's surface, or, a division of these waters, of considerable extent, more or less definitely marked off by land boundaries: the North Sea, or, a large lake or landlocked body of water. §
Sea arch - An arch formed
by wave erosion when caves on opposite sides of a headland unite. §
Sea breeze - A local wind
blowing from the sea during the afternoon in coastal areas. §
Seafloor spreading - The
process of producing new seafloor between two diverging plates. § Seamount
- An isolated volcanic peak that rises at least 1000 meters (3000 feet) above
the deep-ocean floor. § Sea stack - An isolated mass of rock standing just offshore, produced by wave erosion of a headland. §
Seawall - A barrier
constructed to prevent waves from reaching the area behind the wall. Its
purpose is to defend property from the force of breaking §
Secondary enrichment - The
concentration of minor amounts of metals that are scattered through
unweathered rock into economically valuable concentrations by weathering
processes. §
Secondary pollutants - Pollutants
that are produced in the atmosphere by chemical reactions that occur among
primary pollutants. §
Secondary (S) wave - A seismic wave that involves
oscillation perpendicular to the direction of propagation. §
Sediment - Unconsolidated
particles created by the weathering and erosion of rock, by chemical
precipitation from solution in water, or from the secretions of organisms
and transported by water, wind, or glaciers. §
Sedimentary rock - Rock formed from the weathered
products of preexisting rocks that have been transported, deposited, and
lithified. §
Seismic sea wave - A
rapidly moving ocean wave generated by earthquake activity capable of
inflicting heavy damage in coastal regions. §
Seismogram - The record made
by a seismograph. §
Seismograph - An instrument
that records earthquake waves. §
Seismology - The study of
earthquakes and seismic waves. §
Semiarid See Steppe. §
Semidiurnal tidal pattern - A
tidal pattern exhibiting two high tides and two low tides per tidal day with
small inequalities between successive highs and successive lows; a semi-daily
tide. § Sensible heat –
Is potential energy in
the form of thermal energy or heat. The thermal body must have a temperature
higher than its surroundings, (also see: latent heat). The thermal energy can
be transported via conduction, convection, radiation or by a combination
thereof. The quantity or magnitude of sensible heat is the product of the
body's mass, its specific heat capacity and its temperature above a reference
temperature. In many cases the reference temperature is inferred from common
knowledge, i.e. "room temperature". § Shadow zone - The zone between 104 and 143 degrees distance from an earthquake epicenter in which direct waves do not arrive because of refraction by Earth's core. §
Sheeting - A
mechanical weathering process characterized by the splitting off of slablike
sheets of rock. §
Shelf break - The
point where a rapid steepening of the gradient occurs, marking the outer edge
of the continental shelf and the beginning of the continental slope. §
Shield - A
large, relatively flat expanse of ancient metamorphic rock within the stable
continental interior. §
Shield volcano - A broad, gently sloping
volcano built from fluid basaltic lavas. §
Shore - Seaward
of the coast, this zone extends from the highest level of wave action during
storms to the lowest tide level. §
Shoreline - The
line that marks the contact between land and sea. It migrates up and down as
the tide rises and falls. §
Sidereal day - The
period of Earth's rotation with respect to the stars. § Sidereal month
- A time period based on the revolution of the Moon around Earth with respect
to the stars. § Silicate - Any one of numerous minerals that have the oxygen and silicon tetrahedron as their basic structure. §
Silicon-oxygen tetrahedron - A structure composed of four
oxygen atoms surrounding a silicon atom that constitutes the basic building
block of silicate minerals. §
Sill - A
tabular igneous body that was intruded parallel to the layering of preexisting
rock. §
Sinkhole - A
depression produced in a region where soluble rock has been removed by
groundwater. §
Slab pull - A
mechanism that contributes to plate motion in which cool, dense oceanic
crust sinks into the mantle and "pulls" the trailing lithosphere
along. §
Sleet - Frozen
or semifrozen rain formed when raindrops freeze as they pass through a layer
of cold air. §
Slide - A
movement common to mass-wasting processes in which the material moving
downslope remains fairly coherent and moves along a well-defined surface. §
Slip face - The
steep, leeward slope of a sand dune; it maintains an angle of about 34
degrees. §
Slump - The
downward slipping of a mass of rock or unconsolidated material moving as a
unit along a curved surface. §
Snow - A solid form of precipitation produced by
sublimination of water vapor. §
Snowfield - An
area where snow persists year-round. §
Snowline - Lower
limit of perennial snow. § Soil - A combination of mineral and
organic matter, water, and air; that portion of the regolith that supports
plant growth. § Soil horizon A layer of soil that has identifiable characteristics produced by chemical weathering and other soil-forming processes. §
Soil profile - A
vertical section through a soil showing its succession of horizons
and the underlying parent material. §
Soil Taxonomy
- A
soil classification system consisting of six hierarchical categories based on
observable soil characteristics. The system recognizes 12 soil orders. §
Soil texture - The
relative proportions of clay, silt, and sand in a soil. Texture strongly
influences the soil's ability to retain and transmit water and air. §
Solar constant - The rate at which solar
radiation is received outside Earth's atmosphere on a surface perpendicular
to the Sun's rays when Earth is at an average distance from the Sun. §
Solar eclipse - An eclipse of the Sun. §
Solar flare - A
sudden and tremendous eruption in the solar chromosphere. §
Solar winds - Subatomic
particles ejected at high speed from the solar corona. §
Solifluction - Slow,
downslope flow of water-saturated materials common to permafrost areas. §
Solstice - The
time when the vertical rays of the Sun are striking either the Tropic
of Cancer or the Tropic of Capricorn. Solstice represents the longest or
shortest day (length of daylight) of the year. §
Solum - The
O, A, and B horizons in a soil profile. Living roots and other plant and
animal life are largely confined to this zone. §
Sorting - The
process by which solid particles of various sizes are separated by moving
water or wind. Also, the degree of similarity in particle size in sediment or
sedimentary rock. §
Source region - The area where an air mass
acquires its characteristic properties of temperature and moisture. Specific
gravity The ratio of a substance's weight to the weight of an equal volume
of water. § Specific
humidity – The mass of water vapor per unit mass of air, including
the water vapor (usually expressed as grams of water vapor per kilogram of
air). § Spectral class - A classification of a star according to the characteristics of its spectrum. §
Spectroscope - An instrument for directly
viewing the spectrum of a light source. §
Spectroscopy - The
study of spectra §
Spheroidal weathering - Any weathering process that
tends to produce a spherical shape from an initially blocky shape. §
Spicule - A
narrow jet of rising material in the solar chromosphere. §
Spiral galaxy - A flattened, rotating galaxy
with pinwheel-like arms of interstellar material and young stars winding out
from its nucleus. §
Spit - An elongate ridge of sand that projects from
the land into the mouth of an adjacent bay. §
Spring - A flow of groundwater that emerges naturally
at the ground surface. §
Spring equinox - The equinox that occurs on
March 21-22 in the Northern Hemisphere and on September 21-23 in the Southern
Hemisphere. §
Spring tide - Highest tidal range that
occurs near the times of the new and full moons. §
Stable air - Air
that resists vertical displacement. If it is lifted, adiabatic cooling will
cause its temperature to be lower than the surrounding environment; if it is
allowed, it will sink to its original position. §
Stable platform - That part of the era-ton that
is mantled by relatively undeformed sedimentary rocks and underlain by a
basement complex of igneous and metamorphic rocks. §
Stalactite - The
icicle-like structure that hangs from the ceiling of a cavern. § Stalagmite
- The columnlike form that grows upward from the floor of a cavern. § Star dune - Isolated hill of sand that exhibits a complex form and develops where wind directions are variable. §
Stationary front - A situation in which the
surface position of a front does not move; the flow on either side of such a
boundary is nearly parallel to the position of the front. §
Steam fog - Fog having the appearance of steam,
produced by evaporation from a warm water surface into the cool air above. §
Stellar parallax - A measure of stellar distance. §
Steppe - One of the two types of dry climate. A
marginal and more humid variant of the desert that separates it from bordering
humid climates. §
Stony-iron meteorite - One of the three main
categories of meteorites. This group, as the name implies, is a mixture of
iron and silicate minerals. §
Stony meteorite - One of the three main
categories of meteorites. Such meteorites are composed largely of silicate
minerals with inclusions of other minerals. §
Storm surge - The
abnormal rise of the sea along a shore as a result of strong winds. §
Strata - Parallel
layers of sedimentary rock. §
Stratified drift - Sediments deposited by glacial
meltwater. §
Stratopause - The
boundary between the stratosphere and the mesosphere. §
Stratosphere - The
layer of the atmosphere immediately above the troposphere, characterized by
increasing temperatures with height, owing to the concentration of ozone. §
Stratovolcano See Composite cone. §
Stratus - One
of three basic cloud forms; also, the name given one of the flow clouds. They
are sheets or layers that cover much or all of the sky. Streak The color of a
mineral in powdered form. §
Stream valley - The channel, valley floor, and
sloping valley walls of a stream. §
Striations (glacial) - Scratches or grooves in a
bedrock surface caused by the grinding action of a glacier and its load of
sediment. §
Strike-slip fault - A fault along which the
movement is horizontal. §
Stromatolite - Structures
that are deposited by algae and consist of layered mounds of calcium
carbonate. §
Subarctic climate - A climate found north of the
humid continental climate and south of the polar climate and characterized by
bitterly cold winters and short cool summers. Places within this climatic
realm experience the highest annual temperature ranges on Earth. §
Subduction - The process of thrusting oceanic lithosphere
into the mantle along a convergent boundary §
Subduction zone - A long, narrow zone where one
lithospheric plate descends beneath another. §
Sublimation - The
conversion of a solid directly to a gas without passing through the liquid
state. §
Submarine canyon - A seaward extension of a
valley that was cut on the continental shelf during a time when sea level was
lower, or a canyon carved into the outer continental shelf, slope, and rise
by turbidity currents. §
Submergent coast - A coast with a form that is
largely the result of the partial drowning of a former land surface either
because of a rise of sea level or subsidence of the crust or both. §
Subpolar low - Low
pressure located at about the latitudes of the Arctic and Antarctic circles,
In the Northern Hemisphere the low takes the form of individual oceanic
cells; in the Southern Hemisphere there is a deep and continuous trough of
low pressure. §
Subsoil - A
term applied to the B horizon of a soil profile. §
Subtropical high - Not a continuous belt of high
pressure but rather several semipermanent, anticyclonic centers characterized
by subsidence and divergence located roughly between latitudes 25 and 35
degrees. §
Summer solstice - The solstice that occurs on
June 21-22 in the Northern Hemisphere and on December 21-22 in the Southern
Hemisphere. §
Sunspot - A
dark spot on the Sun, which is cool by contrast to the surrounding
photosphere. §
Supercooled - The
condition of water droplets that remain in the liquid state at temperatures
well below 0°C. §
Supergiant - A
very large star of high luminosity. §
Supernova - An
exploding star that increases in brightness many thousands of times. §
Superposition - In any undeformed sequence of
sedimentary rocks, each bed is older than the layers above and younger than
the layers below. §
Supersaturation - The condition of being more
highly concentrated than is normally possible under given temperature and
pressure conditions. When describing humidity, it refers to a relative
humidity that is greater than 100 percent. §
Surf - A
collective term for breakers; also, the wave activity in the area between
the shoreline and the outer limit of breakers. § Surface area -
the area of a rock’s surface exposed to weathering. The more area exposed
the faster chemical weathering can proceed. § Surface soil - The uppermost layer in a soil profile: the A horizon. §
Surface waves - Seismic waves that travel along
the outer layer of Earth. §
Suspended load - The fine sediment carried
within the body of flowing water. §
Swells - Wind-generated
waves that have moved into an area of weaker winds or calm. §
Syncline - A linear downfold in sedimentary strata;
the opposite of anticline. §
Synodic month - The period of revolution of
the Moon with respect to the Sun, or its cycle of phases. §
System - Any
size group of interacting parts that form a complex whole (ES11e, pg 21). § Talus
- An accumulation of rock debris at the base of a cliff. § Tarn - A small lake in a cirque §
Tectonics
- The study of the large-scale processes that collectively deform Earth's
crust. §
Temperate – free
of extremes, mild, (from dictionary.com) §
Temperature - A measure of the degree of hotness
or coldness of a substance; a measure of the average kinetic energy
of individual atoms or molecules in a substance. §
Temperature inversion - A layer in the atmosphere of
limited depth where the temperature increases rather than decreases with height. §
Temporary (local) base level - The level of
a lake, resistant rock layer, or any other base level that stands above sea
level. §
Terminal moraine - The end moraine marking the
farthest advance of a glacier. §
Terrace - A flat, benchlike structure produced by a
stream, which was left elevated as the stream cut downward. §
Terrae - The extensively cratered highland areas of the Moon. §
Terrane - A crustal block hounded by faults, whose
geologic history is distinct from the histories of adjoining crustal blocks. §
Terrestrial planets - Any of the
Earth-like planets, including Mercury, Venus, Mars, and Earth. §
Terrigenous sediment - Seafloorsediments
derived from terrestrial weathering and erosion. §
Texture - The size, shape, and distribution of the
particles that collectively constitute a rock. §
Theory - A well-tested and widely accepted view that
explains certain observable facts. §
Thermal gradient - The increase
in temperature with depth. It averages 1°C per 30 meters (1-2°F per 100 feet)
in the crust. §
Thermal metamorphism See Contact
metamorphism. §
Thermocline - A
layer of water in which there is a rapid change in temperature in the
vertical dimension. §
Thermohaline circulation - Movements of ocean water caused
by density differences brought about by variations in temperature and
salinity. §
Thermosphere - The
region of the atmosphere immediately above the mesosphere and characterized
by increasing temperatures due to absorption of very shortwave solar energy
by oxygen. §
Thrust fault - A low-angle reverse fault. §
Thunder - The
sound emitted by rapidly expanding gases along the channel of lightning
discharge. §
Thunderstorm - A
storm produced by a cumulonimbus cloud and always accompanied by lightning
and thunder. It is of relatively short duration and usually accompanied by
strong wind gusts, heavy rain, and sometimes hail. §
Tidal current - The alternating horizontal
movement of water associated with the rise and fall of the tide. § Tidal delta - A deltalike feature created when
a rapidly moving tidal current emerges from a narrow inlet and slows,
depositing its load of sediment. § Tidal flat - A marshy or muddy area that is covered and uncovered by the rise and fall of the tide. §
Tide - Periodic
change in the elevation of the ocean surface. §
Till - Unsorted
sediment deposited directly by a glacier. §
Tombolo - A ridge of sand that connects an island to
the mainland or to another island. §
Tornado - A
small, very intense cyclonic storm with exceedingly high winds, most often produced
along cold front, in conjunction with severe thunderstorms. §
Tornado warning - A warning issued when a tornado
has actually been sighted in an area or is indicated by radar. §
Tornado watch - A warning issued for areas of
about 65,000 square kilometers (25,000 square miles), indicating that
conditions are such that tornadoes may develop; it is intended to alert
people to the possibility of tornadoes. §
Trade winds - Two
belts of winds that blow almost constantly from easterly directions and are
located on the equatorward sides of the subtropical highs. § Transform fault - A
major strike-slip fault that cuts through the lithosphere and accommodates
motion between two plates. § Transform fault boundary - A boundary in which two plates slide past one another without creating or destroying lithosphere. § Transpiration - The release of water vapor to
the atmosphere by plants. § Transported soil - Soils that form on unconsolidated deposits. §
Transverse dunes - A series of long ridges
oriented at right angles to the prevailing wind; these dunes form where
vegetation is sparse and sand is very plentiful. §
Travertine - A form of limestone (CaCO3) that
is deposited by hot springs or as a cave deposit. §
Trellis pattern - A system of streams in which
nearly parallel tributaries occupy valleys cut in folded strata. §
Trench - An
elongated depression in the seafloor produced by bending of oceanic crust
during subduction. §
Trophic level - A nourishment level in a food chain.
Plant and algae producers constitute the lowest level, followed by herbivores
and a series of carnivores at progressively higher levels. §
Tropical depression - By international agreement, a
tropical cyclone with maximum winds that do not exceed 61 kilometers (38
miles) per hour. §
Tropical rain forest - A luxuriant
broadleaf evergreen forest; also,
the name given the climate associated with this vegetation. §
Tropical storm - By international agreement, a
tropical cyclone with maximum winds between 61 and 119 kilometers (38 and 74
miles) per hour. §
Tropical wet and dry - A climate that is transitional
between the wet tropics and the subtropical steppes. §
Tropic of Cancer - The parallel of latitude, 23
1/2 degrees north latitude, marking the northern limit of the Sun's vertical
rays. §
Tropic of Capricorn - The parallel of latitude, 23
"1 /2 degrees south latitude, marking the southern limit of the Sun's
vertical rays. §
Tropopause - The boundary between the troposphere and the
stratosphere. §
Troposphere - The lowermost layer of the
atmosphere. It is generally characterized by a decrease in temperature with
height. §
Tsunami - The
Japanese word for a seismic sea wave. §
Tundra climate - Found almost exclusively in the
Northern Hemisphere or at high altitudes in many mountainous regions. A
treeless climatic realm of sedges, grasses, mosses, and lichens that is
dominated by a long, bitterly cold winter. §
Turbidite - Turbidity
current deposit characterized by graded bedding. §
Turbidity current - A downslope movement of dense,
sediment-laden water created when sand and mud on the continental shelf and
slope are dislodged and thrown into suspension. §
Turbulent flow - The movement of water in an
erratic fashion often characterized by swirling, whirlpool-like eddies. Most
streamflow is of this type. §
Ultimate base level - Sea level;
the lowest level to which stream erosion could lower the land. §
Ultramafic - Igneous
rocks composed mainly of iron and magnesium-rich minerals. §
Ultraviolet - Radiation
with a wavelength from 0.2 to 0.4 micrometer. §
Umbra - The central, completely dark
part of a shadow produced during an eclipse. §
Unconformity -
A surface that represents a break in the
rock record, caused by erosion or nondeposition §
Uniformitarianism - The
concept that the processes that have shaped Earth in the geologic past are
essentially the same as those operating today. §
Unstable air - Air
that does not resist vertical displacement. If it is lifted, its temperature
will not cool as rapidly as the surrounding environment, so it will continue
to rise on its own. §
Upslope - fog
Fog created when air moves up a slope and cools adiabatically. §
Upwelling - The
rising of cold water from deeper layers to replace warmer surface water that
has been moved away. §
Urban heat island - The fact that
temperatures within a city are generally higher than in surrounding rural
areas. §
Valence electron - The
electrons involved in the bonding process; the electrons occupying the
highest-principal energy level of an atom. §
Valley breeze
- The
daily upslope winds commonly encountered in a mountain valley. §
Valley glacier - See
Alpine glacier. §
Valley train - A
relatively narrow body of stratified drift deposited on a valley floor by
meltwater streams that issue from a valley glacier. §
Vapor pressure
- That
part of the total atmospheric pressure attributable to water-vapor content. §
Vein deposit
- A
mineral filling a fracture or fault in a host rock. Such deposits have a
sheetlike, or tabular, form. §
Ventifact
- A
cobble or pebble polished and shaped by the sandblasting effect of wind. §
Vesicular
- A
term applied to igneous rocks that contain small cavities called vesicles,
which are formed when gases escape from lava. §
Viscosity
- A
measure of a fluid's resistance to flow. §
Visible light - Radiation
with a wavelength from 0.4 to 0.7 micrometer. §
Volatiles
- Gaseous
components of magma dissolved in the melt. Volatiles will readily vaporize
(form a gas) at surface pressures. §
Volcanic bomb
- A
streamlined pyroclastic fragment ejected from a volcano while molten. §
Volcanic island arc - A
chain of volcanic islands generally located a few hundred kilometers from a trench where active subduction
of one oceanic slab beneath another is occurring. §
Volcanic neck - An isolated, steep-sided, erosional remnant
consisting of lava that once occupied the vent of a volcano. §
Volcano
- A
mountain formed of lava and/or pyroclastics §
Warm front -
A front along which a warm air
mass overrides a retreating mass of cooler air. §
Wash
- A
common term for a desert stream course that is typically dry except for
brief periods immediately following a rain. §
Water table - The upper level of the saturated zone of
groundwater. §
Wave (ocean)
- are surface waves that occur in the upper
layer of the ocean. They usually result from wind or
geologic effects and may travel thousands of miles before striking land. They
range in size from small ripples to huge tsunamis. There is little actual forward
motion of individual water particles in a wave, despite the large amount of
energy and momentum it may carry forward. §
Wave (not liquid) - a wave is a mode of energy transfer from one place to
another, often with little or no permanent displacement of the particles of
the medium (i.e. little or no associated mass transport); instead there are oscillations around almost fixed
positions. Thus, while mechanical waves require a medium to transverse the
distance, electromagnetic waves can travel through a vacuum. §
Wave-cut cliff - A
seaward-facing cliff along a steep shoreline formed by wave erosion at its
base and mass wasting. § Wave-cut
platform - A
bench or shelf in the bedrock at sea level, cut by wave erosion. § Wave depth – for the purposes of CRC geology instructions, this is defined as ½ of the wavelength of an ocean wave. It is the depth beneath water surface at which a wave begins to “feel” the bottom. §
Wave height - The
vertical distance between the trough and crest of a wave. §
Wavelength
- The
horizontal distance separating successive crests or troughs. §
Wave of oscillation - A
water wave in which the wave form advances as the water particles move in
circular orbits. §
Wave of
translation - The
turbulent advance of water created by breaking waves. §
Wave period - The
time interval between the passage of successive crests at a stationary
point. § Wave
refraction - See
Refraction. § Weather - The state of the atmosphere at any given time. §
Weathering
- The
disintegration and decomposition of rock at or near Earth's surface. §
Welded tuff - A
pyroclastic rock composed of particles that have been fused together by the
combination of heat still contained in the deposit after it has come to rest
and by the weight of overlying material. §
Well
- An
opening bored into the zone of saturation §
Westerlies
- The
dominant west-toeast motion of the atmosphere that characterizes the regions
on the pole-ward side of the subtropical highs. §
Wet adiabatic rate - The
rate of adiabatic temperature change in saturated air. The rate of temperature
change is variable, but it is always less than the dry adiabatic rate. §
White dwarf
- A
star that has exhausted most or all of its nuclear fuel and has collapsed to
a very small size; believed to be near its final stage of evolution. §
White frost - Ice
crystals instead of dew that form on surfaces when the dew point is below
freezing. §
Wind
- Air
flowing horizontally with respect to Earth's surface. §
Wind vane
- An
instrument used to determine wind direction. §
Winter solstice - The
solstice that occurs on December 21-22 in the Northern Hemisphere and on
June 21-22 in the Southern Hemisphere. §
Yazoo tributary - A
tributary that flows parallel to the main stream because a natural levee is
present. §
Zodiac
- A
band along the ecliptic containing the 12 constellations of the zodiac. §
Zone of
accumulation - The
part of a glacier characterized by snow accumulation and ice formation. Its
outer limit is the snowline. §
Zone of aeration - Area
above the water table where openings in soil, sediment, and rock are not
saturated but filled mainly with air. § Zone of
fracture - The
upper portion of a glacier consisting of brittle ice. § Zone
of saturation - Zone
where all open spaces in sediment and rock are completely filled with water. § Zone
of wastage - The
part of a glacier beyond the zone of accumulation where all of the snow from
the previous winter melts, as does some of the glacial ice. § Zooplankton - Animal plankton. |