Geoscience Reference
In-Depth Information
Pyroclastic material Fragmented rock materials result-
ing from a volcanic explosion or ejection from a volcanic
vent.
rock An amorphous mass of consolidated mineral
matter. 310
rockfall A mass-wasting process in which rocks break
free from cliff faces and rapidly tumble into the valley
below. 382
rock outcrop
361
r
r horizon Unweathered bedrock that underlies soil. 281
radial dikes A long, wall-like feature of intrusive igne-
ous rock that forms when magma is injected into thin cracks
within older rock and cools. 328
radiation Energy that is transmitted in the form of rays or
waves. 70
radiation budget The overall balance between incoming
and outgoing radiation on Earth. 76
radiation fog Fog that develops at night when a temperature
inversion exists. 153
radioactive isotopes Unstable isotopes that emit radioac-
tivity as they decay from one element to another. 324
rain shadow The body of land on the leeward side of a
mountain range that is relatively dry and hot (compared to the
windward side) due to adiabatic warming and drying.
A place where rocks are exposed at the sur-
face of Earth.
311
The internal arrangement of rock
rock structure
layers. 341
rossby waves Undulations that develop in the polar front
jet stream when significant temperature differences exist be-
tween tropical and polar air masses.
120
s
salic horizon The diagnostic horizon of salinization that
forms due to the recrystallization of secondary salts. 296
salinity Concentration of dissolved solids in water that is
measured in parts per thousand (‰). 507
salinization A regional soil-forming process in which
soluble salts are cycled within the soil. 295
salt-crystal growth A weathering process involving the
buildup of salts on rock surfaces through evaporation. These
salts weaken the cement that bonds rock particles, allowing
them later to be washed or blown away. 375
sandstone A sedimentary rock created when individual
sand grains are deposited in thick layers by wind or water and
lithify. 315
saturated zone The zone of rock below and including
the water table where pore spaces are completely filled with
water. 393
scattering The redirection and deflection of solar radiation
by atmospheric gases or particulates. 73
sea A subdivision of an ocean that is partially enclosed by
land. 506
sea breeze Daytime circulatory system along coasts where
winds flow from a zone of high pressure over water to a zone
of relatively low pressure over land. 128
sea fog Fog that develops when cool, marine air comes into
direct contact with colder ocean water. 153
sediment Solid fragments of rocks that are transported to
some location and deposited by wind, water, or ice. 313
sedimentary rocks Rocks that form through the deposition
and lithification of small fragments or dissolved substances
from other rocks or, in some cases, marine animals. 313
seismic waves Vibrations that travel through the Earth
when stress is released in an earthquake. 306
sensible heat Heat that can be felt and measured with a
thermometer. 74
shale Sedimentary rock consisting of lithified clay-sized
sediments.
160
reflection The process through which solar radiation
is returned directly to space without being absorbed by
Earth. 73
regolith The fragmented and weathered rock material that
overlies solid bedrock. 271
relative humidity The ratio between the specific and maxi-
mum humidity of a definable body of air. 143
relief The difference between the high and low elevation of
an area. 274
remote sensing The method through which information is
gathered about the Earth from a distance. 32
residual parent material Parent material that forms by the
weathering of bedrock directly beneath it. 271
retrogradation The process through which a shoreline
retreats through erosion. 517
reverse fault A steeply inclined fault in which the hanging
rock block moves relatively upward. 352
ria A former river valley along the coast that is flooded by
rising sea level. 508
richter scale The logarithmic scale used to measure the
strength of an earthquake. 350
rifting The spreading apart of the Earth's crust by magma
rising between fractures in the Earth's plates. 339
rills Small drainage channels that are cut into hillslopes by
running water. 421
riparian zone The strip of land bordering a body of
water that supports plants and animals adapted to water
systems. 254
roche moutonnée A landform produced by glacial abrasion
and plucking that has a shallow slope on one side and a steep
slope on the other side.
457
315
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