Glossary of Terms: B

Background Extinction

Normal extinction of species that occurs as a result of changes in local environmental conditions. Also see mass extinction.

 

Backscattering

Portion of solar radiation directed back into space as a result of particle scattering in the atmosphere.

 

Backshore

Area behind the shore. This coastal feature is located between the beach berm and the backshore slope.

 

Backshore slope

Sloping bank landward of the shore. 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 of gravity.

 

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 channel.

 

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 square centimeter.

 

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 coasts.

 

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 rock.

 

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.

 

Base 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 than 7.

 

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 solution.

 

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.

 

Bedding 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 tide level.

 

Bergschrund

A deep crevasse commonly found at the head of an alpine glacier. Forms when the glacial ice pulls away from the mountain side.

 

Berm

Low hill of sand that forms along coastal beaches.

 

Bermuda High

High pressure system that develops over the western subtropical North Atlantic. Also called Azores High.

 

Beta Particle

Electron emitted from the nucleus of a radioactive isotope. Also see alpha particle and gamma rays.

 

B Horizon

Soil horizon normally found below the A horizon and above the C horizon. This layer is characterized by the following features:

(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 clay particles.

 

Biennial Plant

Plant species that completes its life in two growing seasons.

 

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 (ecosystem diversity). 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.

 

Biogeography 

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 levels.

 

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 nails.

 

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 animals, 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 hollow.

 

Body Wave

Type of seismic wave that travels through the interior of Earth.

 

Bog

A habitat that consists of waterlogged spongy ground. Common vegetation are sedges and sphagnum moss. 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 water).

 

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, and Bromelioideae.

 

Brunisol 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 horizon.

 

 

Citation: Pidwirny, M. (2006). "Glossary of Terms: B". Fundamentals of Physical Geography, 2nd Edition. Date Viewed. http://www.physicalgeography.net/physgeoglos/b.html