geography 15-17

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Hygroscopic water

Soil water held so tightly by sediment grains that it is unavailable for plant use.

Field Capacity

The amount of water remainig in the soil after the soil is completely drained of gravitational water.

Unsaturated zone

The area between the soil water belt and the water table where pore spaces arenot saturated with water.

Aquiclude

An impermeable body of rock that may contain water but does not allow transmission of water through it.

Saturated zone

The zone of rock below and including the water table where pores spaces are completely filled with water.

Aquifer

A geological formation that contains a suitable amount of water to be accessed for human use.

Water Table

The top of the saturated zone.

Artesian well

A well in which water form a confined aquifer rises to the surface through natural pressure.

Cone of depression

Teh cone-shaped depression of water the water table that occurs around a well.

Subsidence

The sttling or sinking of a surface as a result of the loss of suport fom underlying water, soils, or strata.

Karst topography

Terrain that is generally underlain by soluble rocks, such as limestone and dolomite, where the landscape evolves largely through the dissolution of rock.

Cave

A cavity in rock, produced by the dissolution of calcium carbonate, that is lrge enough for someone to enter.

Sinkhole

A topographic depression that forms when underlying rock dissolves, causing the surface to collapse.

Disappearing Stream

A surface river or stream that flows into a sinkhole and subsequently moves into an underground river system.

Drainage basin

The geographical area that ocntributes groundwater and runoff to any particular stream.

Drainage divide

An area of raised land that forms a seperating rim between two adjacent drainage basins.

Trunk Stream

The primary stream of a drainage basin.

Tributary

A stream of river that flows into a larger tream or river.

Interfluves

Topographic high points in a drainage basin that seperate one tributary from another.

Confluence

The place where two streams join together.

Drainage density

The measure of stream channel length per unit area of drainage basin.

Base Flow

The amount of stream discharge at any given place and time that is solely the product of groundwater seepage.

Bankfull discharge

The amount of discharge at which the stream channel is full.

Stream hydrograph

The graphical representation of stream discharge over a period of time.

Flood stage

The level at which stream discharge begins to spill out of the channel into the surrounding area.

Rills

Small drainage channels that are cut into hill slopes by running water.

Meandering stream

A river or small stream that curves back and forth across its valley.

Braided stream

A network of converging and diverging stream channels within an individual stream system that are seperated from each other by deposits of sand and gravel.

Aggradation

The progressive accumulation of sediment along or within a stream.

Degradation

The topographic lowering of a stream channel by stream erosion.

Graded Stream

A stream that is capable of transporting the average sediment load provided to it over time.

Longitudinal profile

A graph that illustrates the change in stream gradient in cross section along a stream from its source to its mouth.

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.

Oxbow lake

A portion of an abandoned stream channel that is cut off from the rest of the stream by the meandering process and is filled with stagnant water.

Natural levee

A small ridge that develops along the channel of a stream through the deposition of relatively coarse sediment when flooding occurs.

Backswamps

Marsh floodplain landforms that develop behind natural levees in which fine-grained sediments settle after a flood.

Alluvial terrace

A level, step-like landform that forms when a stream erodes its bed so that an essentially horizontal surface is raised relative to the channel.

Alluvium

Sediment deposited by a stream.

Alluvial fan

A fan-shaped landform of low relief that forms where a stream flows out of an area of high relief into a broad, open plane where the gradient is less and deposition occurs.

Delta

A low, level plain that develops where a stream flows into a relatively still body of water so that its velocity decreases and alluvial deposition occurs.

Artificial levee

An engineered structure along a river that effectively raises the height of the river bank and thus confines flood discharge.

Dam

A barrier that blocks or restricts the downstream movement of a stream.

Glacier

A slow-moving mass of dense ice.

Firn

The compact, granular substance that is the transition stage between snow and glacial ice.

Zone of accumulation

The geographical region where snow accumulates and feeds the growth of a glacier.

Zone of ablation

The part of a glacier where melting exceeds snow accumulation.

Equilibrium line

The place on a glacier where snow accumulation and melting are in balance.

Crevasse

A deep crack in a glacier.

Ice cap

A large ice mass in mountainous regions that is approximately circular in form.

Ice field

A large ice mass in mountainous regions that is generally linear in form.

Alpine glacier

A glacier in mountainous regions that flows down pre-existing valleys.

Cirque

A bowl-like depression that serves as a source area for some alpine glaciers.

Continental glacier

An enormous body of ice that covers a significant part of a large landmass.

Glacial abrasion

An erosional process caused by the grinding action of a glacier on rock.

Glacial striations

Scratches in rock produced by glacial abrasion.

Glacial grooves

Deep furrows in rock produced by glacial abrasion.

Glacial plucking

An erosional process by which rocks are ripped out of the ground by a glacier.

Glacial erratics

Large boulders that have been plucked and transported a great distance before they are deposited.

Roche moutonnee

A landform produced by glacial abrasion and plucking that has a shallow slope on one side and a steep slope on the other side.

Tarn

A small lake that forms within a glacial cirque.

Arete

A sharp ridge that forms between two glacial cirques.

Horn

A mountain with three or more aretes on its flanks.

Glacial trough

A deep, U-shaped valley carved by an alpine glacier.

Hanging valley

An elevated U-shaped valley (with respect to a glacial through) formed by a tributary alpine glacier.

Glacial drift

Sediment deposited indirectly or directly by a glacier.

Glacial till

Sediment deposited directly by a glacier.

Moraine

A winding ridge-like feature that forms at the front or side of a glacier or between two glaciers.

Drumlin

A streamlined landform created when a glacier deforms previously deposited till.

Glacial outwash

Sediment deposited by meltwater streams emanating from a glacier.

Outwash plain

A broad landscape of limited relief created by deposition of glacial outwash.

Kame

A large mound of sediment deposited along the front of a slowsly melting or stationary glacier.

Esker

A winding ridge formed by a stream that flows beneath a glacier.

Kettle lake

A lake that forms when a block of ice falls off the glacial front, is buried by glacial drift, and then melts, forming a depression that fills with water.

Laurentide Ice Sheet

The continental glacier that covered eastern Canada and parts of northeastern United States during Pleistocene Epoch.

Cordilleran Ice Sheet

The ice cap that covered much of the mountains in the northwestern part of North America during the Pleistocene Epoch.

Oxygen isotope stages

Periods of time that have distinct 0-18/0-16 ratios, which are used to reconstruct prehistoric climate change.

Milankovitch theory

The theory that best explains Pleistocene glacial interglacial cycles through long-term variations in the Earth's orbited eccentricity, tilt, and axial precession.

Periglacial processes

The suite of processes involving frost aaction, permafrost, and ground ice that occurs in artic enviornments or along the margins of ice sheets.

Permafrost

Ground that is permanently frozen.

Ground ice

Distinct zones of frozen water that occur in permafrost regions.

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