Glossary of Terms: B
- Background Extinction - Normal extinction of species that
occurs as a result of changes in local environmental
conditions. Also see mass
- Backscattering - Portion of solar
radiation directed back into space as
a result of particle scattering in
- Backshore - Area behind the shore.
This coastal feature is located between the beach berm and
the backshore slope.
- Backshore slope - Sloping bank landward of
This coastal feature is composed of relatively non-mobile sediments.
- Backswamp - Marshy low lying area in a stream's floodplain.
Commonly found behind levees.
- Backwash - The return water flow of swash.
This sheet of water flows back to ocean because
- Bacteria - Simple single celled prokaryotic organisms.
Many different species of bacteria exist. Some species
of bacteria can be pathogenic causing
disease in larger more complex organisms. Many species
of bacteria play a major role in the cycling of nutrients in
ecosystems through aerobic and anaerobic decomposition. Finally, some species form symbiotic relationships
with more complex organisms and help these life forms
survive in the environment by fixing atmospheric nitrogen.
- Badlands - (1) Term used to describe a part of South Dakota. (2) Term used to describe a semi-arid landscape
that has been influenced by heavy fluvial erosion.
Characterized by deep ravines and gullies, shape
ridges, and a generally barren surface.
- Bajada - Consecutive series of alluvial
fans forming along the edge of a linear
mountain range. Surface of this feature undulates
in a rolling fashion as one moves from the center
of one alluvial fan to another. Normally occurs
in arid climates.
- Bank-Caving - Collapse of stream
bank material into a stream
- Bar - (1) Coarse grained deposit of sediment from
a stream or ocean currents. (2) A unit of measurement for quantifying force.
Equivalent to 1,000,000 dynes per
- Barchan Dune - Crescent shaped sand
dune that has its long axis transverse
to the wind and its crescent tips pointed downwind.
- Barometer - Instrument that measures atmospheric pressure.
- Barrier Beach - A long and narrow beach of sand and/or gravel that runs parallel to the coastline and
is not submerged by the tide.
- Barrier Island - Long, narrow islands of sand and/or gravel that
are usually aligned parallel to the shore of some
- Basal Sliding - The sliding of a glacier over
the surface it rests on. Caused by the gradient of
the slope and the weight of the glacier's mass.
- Basalt - A dark colored fine grained igneous
rock formed from mafic magma.
- Basalt Plateau - Extensive continental deposits of basaltic volcanic
- Basaltic Magma - Mafic magma that
forms basaltic igneous rocks.
- Base - (1) Substance having a pH greater
than 7. (2) Substance that releases hydroxide ions (OH-).
- Base Flow - Rate of discharge in
a stream where
only the throughflow and groundwater
flow from subsurface aquifers contribute
to the overall flow.
Level - The subterranean elevation below which a stream cannot
vertically erode sediment.
For many streams this hypothetical elevation is sea-level.
- Basement Rock - Very old granite and metamorphic
rocks found in continental
crust. These rocks make up the continental shield.
- Basic - Substance having a pH greater
- Basic Solution - Any water solution that is basic (pH
greater than 7) or has less hydrogen ions (H+) than
hydroxide ions (OH-). Also see acidic
solution and neutral
- Basin - A topographic rock structure
whose shape is concave downwards.
- Batholith - A large mass of subsurface intrusive
igneous rock that has its origins from mantle magma.
- Bay - A body of sheltered water found in a crescent shaped
coastal configuration of land.
- Bayhead Beach - An extensive deposit of sand and/or gravel in
the form of a beach at
the back of a bay.
- Bay-Mouth Bar - A narrow deposit of sand and/or gravel found
across the mouth of a bay.
- Beach - The terrestrial interface area in between land
and a water body where there are accumulations of
unconsolidated sediments like sand and gravel. These deposits are
laid down by the action of breaking waves.
- Beach Drift - The lateral movement of sediments on
a beach when the
angles of swash and backwash differ.
- Bearing - A system that measures in reference to the cardinal
points of a compass in 90 degree quadrants.
- Beaufort Wind Scale - Descriptive system that determines wind speed
by noting the effect of the wind on the environment.
Originally developed for use at sea by Admiral Beaufort
of the British Navy in 1806.
- Bed - Sedimentary structure that usually represents a
layer of deposited sediment.
Plane - A layer in a series of sedimentary beds that
marks a change in the type of deposits.
- Bed Load - Portion of the stream
load that is carried along the stream
bed without being permanently suspend
in the flowing water.
- Bedrock - Rock at
or near (beneath soil and regolith) the Earth's surface that is solid
and relatively unweathered.
- Benthos - The plant and animal organisms that live on the sea floor.
Often divided into two categories: deep-sea
benthos, below 200 meters and the littoral
benthos, from 200 meters to the high-water spring
- Bergschrund - A deep crevasse commonly
found at the head of an alpine glacier.
Forms when the glacial ice pulls away from the mountain
- Berm - Low hill of sand that
forms along coastal beaches.
High - High pressure system
that develops over the western subtropical North
Atlantic. Also called Azores
- Beta Particle - Electron emitted
from the nucleus of
a radioactive isotope.
Also see alpha particle and gamma
- B Horizon - Soil horizon normally
found below the A
horizon and above the C
horizon. This layer is characterized by the
- (1) Enrichment of clay because
of illuviation from
the A horizon.
- (2) Enrichment of iron and aluminum oxides because
of illuviation of these materials from the
A horizon. In some cases the precipitation of iron
can cause the development of a hardpan.
- (3) Accumulation of calcium carbonate, calcium
sulfate, and other salts.
- (4) Higher bulk density because of the illuvial deposition of
- Biennial Plant - Plant species that completes its life in two growing
- Bifurcation Ratio - Quantitative ratio determined between the parts
of systems that display branching. For example,
trees have a main stem that bifurcates into smaller
and smaller branches. The ratio between the branches
that are derived from a larger branch or main stem
is the bifurcation ratio.
- Big Bang - Theory that suggests that about 15 billion years
ago all of the matter and energy in the Universe was
concentrated into an area smaller than a atom. At
this instant, matter, energy, space and time did
not exist. Then suddenly, the Universe began to expand
at an incredible rate and matter, energy, space and
time came into being. As the Universe expanded, matter
began to coalesce into gas clouds, and then stars
and planets. Some scientists believe that this expansion
is finite and will one day cease. After this point
in time, the Universe will begin to collapse until
a Big Crunch occurs.
- Big Crunch - Collapse of the Universe into
its original form before the Big
Bang. At the end of this process matter,
energy, space, and time will not exist.
- Biodiversity - The diversity of
different species (species
diversity), genetic variability among individuals
within each species (genetic diversity), and variety of ecosystems
Abbreviation of biological diversity.
- Biogeochemical Cycling - Cycling of a single element, compound or
chemicals by various abiotic and biotic processes
through the various stores found in the biosphere, lithosphere, hydrosphere, and atmosphere.
- Field of physical
geography that studies the spatial pattern
of living organisms.
- Biological Amplification - Increase in concentration of toxic fat-soluble
chemicals in organisms at successively higher trophic
levels of a grazing food chain or food web because of the consumption of
organisms at lower trophic
- Biological Weathering - The disintegration of rock and mineral due
to the chemical and/or physical agents of an organism.
- Biomass - The weight of living tissues usually measured per
unit area over a particular time interval. Can include
the dead parts of organisms like bark, hair, and
- Biome - Largest recognizable assemblage of animals and plants on
the Earth. The distribution of the biomes is controlled
mainly by climate.
- Bioregion - A unique region on the Earth that has distinct
soils, landforms, watersheds, climates, native plants,
and/or other particular natural characteristics.
- Biosphere - Part of the Earth where life is found. The biosphere
consists of all living things, plant and animal.
This sphere is characterized by life in profusion,
diversity, and clever complexity. Cycling of matter
in this biosphere involves not only metabolic reactions
in organisms, but also many abiotic chemical
reactions. Also called ecosphere.
- Biotic - (1) Referring to life. (2) Influences caused by living organisms.
- Biotic Potential - Maximum rate that a population of
a given species can
increase in size (number of individuals) when there
are no limits on growth rate.
- Biotite - Rock forming mineral of
the mica group.
- Bird - Group of warm blooded vertebrate animals whose
body is covered with feathers.
- Black Body - Is a body that emits electromagnetic
radiation, at any temperature,
at the maximum possible rate per unit surface
area. This body also absorbs all electromagnetic
radiation that is intercepted by it.
- Blizzard - Winter severe weather condition characterized by
strong wind, blowing snow, and cold temperatures.
- Blowout Depression - Saucer shaped depressions created by wind erosion.
At the leeward end of the feature there usually
is a deposit of
sand. Blowouts are found in coastal beach areas and
in arid and semiarid regions of the world. These
features are smaller than a deflation
- Body Wave - Type of seismic
wave that travels through the interior
- Bog - A habitat that consists of waterlogged spongy ground.
Common vegetation are sedges and
Bogs are common in Canada, Russia, and Scandinavia.
- Bolson - Is a closed desert basin with no drainage outlet,
surrounded by mountains.
- Boulder - Large fragment of rock that
has a diameter greater than 256 millimeters (200
millimeters in the United Kingdom).
- Bora - Term used to describe a katabatic
wind in Yugoslavia.
- Boreal Forest - High to mid-latitude biome dominated
by coniferous forest.
Predominant vegetation of this biome is various species
of spruce, fir, pine, and cedars. Also called Taiga.
- Bottomset Bed - Horizontal deltaic deposit
of alluvial sediment composed of fine silt and clay.
- Bowen Reaction Series - Model that explains the origin of the various types
of igneous rocks. It suggests that the presence
or absence of particular minerals in
igneous rocks depends on the temperature of crystallization
and on the magma's original chemical composition.
- Brackish - Environment that is influenced by seawater with
a salinity less
than 35 parts per thousand (usually caused by the
presence of an inflow of fresh
- Braided Stream - Shallow stream channel that is subdivided into a number
of continually shifting smaller channels that are
separated by bar deposits.
- Breaker - The quick collapse of an overextended water wave as
it approaches the shoreline.
The collapse occurs when the ratio of wave
height to wavelength exceeds
1:7. This phenomenon also produces swash.
- Breccia - Coarse grained sedimentary
rock composed of cemented angular rock fragments.
- Brine - Seawater with
a salinity greater
than 35 parts per thousand. Usually occurs in isolated
bodies of seawater that have high amounts of water
loss due to evaporation.
- British Thermal Unit (Btu)
- Measurement unit for heat.
It is the amount of energy required to raise the
temperature of one pound of water one degree from
62 to 63° Fahrenheit. One Btu is equal to 252 calories and
to 1055 joules.
- Bromeliad - Plants of
the bromeliad family (Bromeliaceae).
These plants grow from the dry deserts of the subtropics
to equatorial tropical rain forests. Many bromeliads
grow high up on the branches and trunks of trees
in the tropical rainforest. Based on growth habits
and other characteristics, Bromeliaceae is divided
into the subfamilies Pitcairnioideae, Tillandsioideae,
Soil - Soil order
(type) of the Canadian
System of Soil Classification. This soil
type is associated with forest vegetation. It is
usually poorly developed and immature. The most identifying
trait of this soil is the presence of a brown B
M. (2010). "Glossary of Terms: B". In: Glossary of Terms, www.our-planet-earth.net. Date