Geoscience Reference
In-Depth Information
B
B horizon
The soil horizon that forms below the E horizon
because translocated minerals recrystallize. 281
Backshore
The part of the beach that lies between the berm
scarp and foredune and is covered by water only during strong
storms. 519
Backslope
The gradual slope of a dune that faces the
prevailing winds. 490
Backswamps
Marshy floodplain landforms that develop
behind natural levees in which fine-grained sediments settle
after a flood. 431
Bajada
A landscape consisting of overlapping alluvial fans
along a mountain front. 484
Bankfull discharge
The amount of discharge at which the
stream channel is full. 417
Barrier island
An elongated bar of sand that forms parallel
to the shore for some distance. 522
Base flow
The amount of stream discharge at any given
place and time that is solely the product of groundwater
seepage. 416
Base level
The lowest level at which a stream can no longer
lower its bed, because it flows into the ocean, a lake, or
another stream. 425
Bay
An indentation in the shoreline that is generally associ-
ated with an ocean, sea, or gulf. 507
Baymouth bar
A spit that entirely encloses a bay. 521
Beach drift
Sediment that is transported in the surf zone by
swash and backwash, which form due to the oblique approach
of waves. 513
Berm scarp
A miniature cliff created by wave erosion that
fronts a beach berm. 519
Big Bang theory
The theory that the Universe originated
about 14 billion years ago when all matter and energy
erupted from a singular mass of extremely high density and
temperature. 44
Biomass
The amount of living matter in an area, including
plants, animals, and insects. 239
Biome
The complex of living communities maintained by
the climate of a region and characterized by a distinctive type
of vegetation. 241
Biosphere
The portion of Earth and its atmosphere that
supports life.
Butte
A steep-sided hill or peak that is often a remnant of a
plateau or mesa.
483
C
C horizon
Unaltered soil parent material. 281
Calcic horizon
A diagnostic soil horizon of calcification
enriched in illuviated calcium carbonate. 293
Calcification
A regional soil-forming process in which
calcium carbonate is cycled within the soil. 292
Canyon
A very steep-sided valley that is cut into
bedrock. 483
Capillary action
The process through which water is able to
move upward against the force of gravity. 138
Caprock
A unit of relatively resistant rock that caps the
top of a landform and thus protects underlying rocks from
erosion. 372
Carbonation
A type of chemical weathering caused by
rainwater that has absorbed atmospheric carbon dioxide
and formed a weak carbonic acid that slowly dissolves
rock. 378
Carrying capacity
The maximum number of organisms that
can live in a given area of habitat without degrading it and
causing social stresses that result in population decline.
538
Cartography
The design and production of maps. 22
Cation exchange capacity (CEC)
The total amount of
exchangeable cations that a soil can absorb. 279
Cations
Positively charged ions, such as sodium, potassium,
calcium, and magnesium. 279
Cave
A cavity in rock, produced by the dissolution of
calcium carbonate, that is large enough for someone to
enter. 402
Celestial dome
A sphere that shows the Sun's arc, relative
to the Earth, in the sky. 54
Chemical weathering
The decomposition and alteration
of rocks due to chemical actions of natural physical and
biological processes. 375
Chinook winds
Downslope airflow that results when a zone
of high air pressure exists on one side of a mountain range and
a zone of low pressure exists on the other. 129
Cinder-cone volcano
A small, steep-sided volcano that con-
sists of solidified magma fragments and rock debris that may
form in only one eruption. 361
Circle of illumination
The great circle on Earth that is the
border between night and day. 47
Cirque
A bowl-like depression that serves as a source area
for some alpine glaciers. 455
Cirrus clouds
Thin, wispy clouds that develop high in the
troposphere. 153
Climate
Average precipitation and temperature
characteristics for a region that are based on long-term
records.
8
Bioturbation
The mixing of soil by plants or animals.
272
Brackish
Water that has salinity less than 35‰. 507
Braided stream
A network of converging and diverging
stream channels within an individual stream system that
are separated from each other by deposits of sand and
gravel. 422
Breaker
A wave that rises and crashes when the forward
momentum of oscillations cannot be maintained.
512
Water that has salinity greater than 35‰.
507
202
Brine
