Geology Glossary Part 2

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accordant

drainage pattern controlled by the structures over which the stream or river flows

acre foot

unit of volume used for lakes and reservoirs equal to an area of 1 acre to a depth of 1 foot

adret

the sunny slope of a valley favored for farming

aggradation

raising of level of the land surface b/c inability of river to transport its load leading to deposition

alluvial fan

large pile of sediment that usually forms @ apex

apex

point of emergence of a stream from mountains

alluvium

products of sedimentation by rivers

antecedent

describing a stream that maintains its original course despite later deformation of the land

bank

either side of a river channel

bar

ridge of sediment deposited in the middle or along the banks of a stream

bayou

marshy area of an estuary or where a lake outflows

bed load

material carried along the bottom of a stream or sea by moving water or along the ground by the wind

bluff

steeply sloped river bank on the outside of a meander

bog

waterlogged area of land b/c poor drainage; no standing water; vegetation partly decomposes to acid peat

braided stream

a stream that flows in a network of interconnected rivulets around numerous bars before rejoining

canyon

deep, steepsided section of a river valley in arid or semiarid regions

capacity

total load that a stream can carry as bedload

catchment area

the area from which a river and its tributaries obtain their water

cavitation

type of erosion in fast streams where bubbles form and collapse exerting stress on channel walls

competence

largest size of grain that a stream can move as bed load

delta

body of sediment deposited at the mouth of a river when the river velocity decreases

wave-dominated delta

delta w/ barrier islands along oceanward side

tide-dominated (delta)

strong ties reshape the sediment into tidal bars aligned parallel to a tidal current

stream-dominated delta

sedimentation forms fingerlike distributaries; aka bird footed

foreset beds

main body of the delta deposited at an angle to the horizontal

topset beds

nearly horizontal beds of varying grain size above the foreset

bottomset beds

deposits of the finest sediment in front of foreset

dendritic

describing drainage pattern like the branches of a tree, entirely random b/c of uniform lithology

deranged

describing drainage pattern of recently glaciated areas; not coordinated w/ many small local drainage basins and lakes

discharge

the volume of water that flows past a given point in a unit of time; multiply cross-sectional area by velocity.

dissolved load

part of a river‟s load carried in chemical solution

distributary

small river channel carrying water away from the main river w/o rejoining it

divide

area of higher ground separating one drainage basin from another

drainage basin

the total area drained by a stream and its tributaries

downcutting

valley-deepening process caused by erosion of a stream bed

base level

theoretical limit for erosion of the Earth's surface

effluent

stream that flows out of a lake or other stream

effluent

waste material discharged as a liquid from a sewer or nuclear power plant

ephemeral stream

stream that contains water only immediately after rainfall

epilimnion

warm upper layer of water in a lake or shallow sea w/ photosynthesis

flash flood

local flood with a large volume and short duration from thunderstorms

flood

the state of a river when the volume of water flowing in it exceeds bankfull

floodplain

level area bordering a river made up of sediments deposited by the river

fluvial

of or relating to a river

frazil ice

small crystals of ice that form at the edges of fast-flowing streams or in moving seawater

gaining stream

stream that receives water from the zone of saturation

gorge

narrow steep valley formed in hard rocks by erosive action of stream or river

graded stream

stream exhibiting a delicate balance btwn transporting capacity and sediment load available

gully

small narrow channel on hillside w/o vegetation formed by the rapid runoff

headward (headwater) erosion

increase in length of valley b/c erosion at the upper end

headwaters

upper part of a stream near its source in the mountains

helical flow

most significant turbulence in streams; net corkscrew movement

hydraulic action

he ability of flowing water to dislodge and transport particles

hydrography

study of water bodies on Earth and the strips of land bordering them

hypolimnion

cool lower layer in a lake or shallow sea w/o photosynthesis

incised meander

meander of a stream that is cut deeply into bedrock

intermittent stream

stream that flows only certain times of the year

lake

body of water completely surrounded by land in a depression

Lake Bonneville

prehistoric pluvial lake that covered much of North America's Great Basin region; now Great Salt Lake

laminar flow

slow smooth flow w/ each drop of water traveling parallel to its neighbor

limnology

the scientific study of lakes and other bodies of freshwater

lateral erosion

erosion and undercutting of stream banks b/c stream swinging from side to side across its valley

levee

low ridge of flood-deposited sediment formed on either side of a stream channel

load

material that is moved or carried by a natural transporting agent

loch

Scottish name for a lake

losing stream

stream that loses water to the zone of saturation

meander

pronounced sinuous curve along a stream‟s course

meander cutoff

new, shorter channel across the narrow neck of a meander

meander scar

abandoned meander filled with sediment and vegetation

misfit river

river that is apparently too small for its valley

mouth

place where a stream enters a larger body of water

muskeg

type of bog that occurs in tundra areas b/c melting permafrost

oligotrophic

describing a lake/other body of water deficient in plant nutrients w/ very clear water

oxbow (lake)

crescent-shaped lake in abandoned meander isolated by a meander cutoff

perennial (stream)

a stream or river that flows permanently throughout the year

placer deposit

place in a stream where the running water has mechanically concentrated heavy sentiment

pluvial period

period of time w/ greater rainfall than other periods, oft on geologic timescale

pluvial lake

lake formed during an earlier time of abundant rainfall

point (bar)

stream bar deposited on the inside curve of a steam

pothole

depression eroded in stream bed by abrasive action of sediment load

radial drainage pattern

drainage pattern in which streams diverge outward like spokes of a wheel; on mtns

rapids

stretch of fast-flowing turbulent broken water over series of small steps

ravine

small narrow deep-sided valley carved by river

rectangular drainage pattern

drainage pattern where tributaries join each other at right angles; on rock with regular fractures

recurrence interval

the average time between floods of a given size

rejuvenation

action of stimulating a stream to renewed erosive activity

riparian

pertaining to or situated on the bank of a body of water (oft river)

riparian rights

principle that all landowners w/ property adjacent to a stream have the right to use it

rill

minute ephemeral channel @ head of drainage systems forming where sheet wash is concentrated

saltation

mvmt of bed load by short leaps or bounces off the bed

sheetwash

thin layer of unchanneled water flowing downhill

soda lake

alkali lake w/ high dissolved sodium salt content (Na2CO3)

stream

moving body of water in a channel running downhill b/c gravity

streambed

bottom of the channel through which a stream flows

stream cross section

V-shaped valleys

stream gradient

downhill slope of the bed of a stream (ft/mi)

stream headwaters

upper part of a stream; near the source

stream mouth

place where a stream enters a larger body of water

stream order

classification of a stream in drainage system

(stream) piracy

natural diversion of the headwaters of one stream into the channel of another w/ more erosion

stream velocity

the distance water travels in a stream per unit time

suspended load

sediment in a stream light enough in weight to remain lifted indefinitely

swamp

area of soft wet land w/ poor drainage and trees

thalweg

line connecting the lowest points along a stream bed or valley

topset bed

in a delta, a nearly horizontal sediment bed of varying grain size

tortuosity

the ratio of the actual (middle) length of a river channel to its axial length

traction

movement by rolling, sliding, or dragging of sediment along bed

trellis (drainage pattern)

drainage pattern w/ parallel main streams with short tributaries meeting them at right angles; parallel ridge & valley

tributary

a stream which flows into another

turbulent flow

eddying swirling flow where water drops travel along erratic path

V-shaped valley

characteristic profile of a stream-cut valley

waterfall

vertical wall of water; steep break in profile of stream

watershed

aka drainage basin

yazoo stream

tributary stream that flows parallel to the mainstream for awhile

acid (mine) drainage

water from coal and metal mines that contain sulfuric acid

aquifer

body of saturated rock through which water can move readily (yields groundwater)

aquitard

body of rock that prevents the movement of groundwater

artesian

describing water that moved underground from its original source

artesian well

well in which water rises to a level above the top of the aquifer

capillarity

mechanism whereby capillary water moves vertically up the soil profile

capillary water

water held in small pores within soil, existing as a film around particles; used by plants

cave(rn)

naturally formed underground chamber oft b/c acid + limestone

concretion

hard, rounded mass of cementing material carried into place by groundwater

cone of depression

depression of water table; formed around a well when water is pumped out

confined (artesian) aquifer

aquifer completely filled with pressurized water and separated from the land surface by aquitard

darcy

unit used to measure the porosity of rock; represents resistance of fluid to flow through it

Darcy's law

rate of flow through a porous material prop to product of permeability and pressure

drawdown

lowering of the water table near a pumped well

dripstone

deposits of calcite built up by dripping water in caves

field capacity

the maximum amount of water a soil can retain after gravitational water has drained away

gaining stream

stream that receives water from the saturated zone

geode

partly hollow, globe-shaped rock with crystals in cavity

geothermal energy

energy produced by harnessing naturally occurring steam and hot water

geyser

type of hot spring that periodically erupts hot groundwater & steam

groundwater

water that lies beneath the surface

hardpan

layer of hard material just below surface preventing good drainage

hard (water)

natural water w/ dissolved Ca Mg ions; + soap = scum

hot spring

spring in which the water is warmer than human body temperature

hydrologic cycle

mvmt of water (sea->atm->land->sea)

hydrology

study of the properties, distribution, and circulation of water

hydrosphere

all the waters of the Earth

hydrostatic pressure

pressure exerted by a liquid

impermeable

describing a rock that is nonporous and therefore does not absorb water

impervious

describing rock w/o cracks or fissures so does not allow water to pass through

infiltration

the movement of water downward into the ground

karst topography

area with many sinkholes and a cave system beneath the land surface of limestone

losing stream

stream that loses water to the saturated zone

mud pot

type of hot spring containing boiling mud

perched water table

water table separated from main water table beneath by unsaturated zone

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