Unit 9: Weathering, Erosion and Hydrology (H) 2025

abrasion

The grinding away of rock by contact with other rock particles carried in water, ice, or wind

animal burrowing

the weathering of rock by animal or insect digging

aquifer

A body of rock or sediment that stores groundwater and allows the flow of groundwater.

bedload

the larger sediment carried along the bed of the river

butte

An isolated hill with steep sides and a flat top (similar to but narrower than a mesa).

cap stone

protects softer rock in the column below

capacity

the amount of sediment a stream carries based on its discharge

Chemical weathering

the processes by which the internal structure of a mineral is altered by the removal and/or addition of elements

columnar joints

a pattern of cracks that forms during cooling of molten rock to generate columns

competence

the maximum size sediment a stream can carry given its velocity

cone of depression

lowering of the water table around a pumping well

continental divide

mountain ridge that separates drainage basins flowing toward opposite sides of a continent, in the US it is toward the Atlantic Ocean and the Pacific Ocean

creep

when soil moves down hill very slowly, imperceptible

cut-off

the shortcut with a steeper gradient that a river takes between two meanders

cutbank

eroded stream bank on the outside of a meander curve

delta

A landform made of sediment that is deposited where a river flows into an ocean or lake

Deposition

Process in which sediment is laid down in new locations.

desert varnish

a black coating that forms on the surface of a rock when the air interacts with magnesium

discharge

the amount of water flowing through a river in a given amount of time calculated as cross-sectional area x velocity

dissolved load

The stream load of dissolved materials such as sodium and calcium.

distributary

When a river branches off of the trunk stream at the mouth of the river, and is located in the delta.

divide

a high point or ridge that determines the direction that water flows, separating two drainage basins

drainage basin

the land area bordered by divides that contributes water through runoff and groundwater to a river system

Erosion

the physical removal of material by mobile agents such as water, wind, or ice.

exfoliation

A mechanical weathering process in which rock layers that have cracked perpendicular to the expansion direction of intrusive igneous rocks that have undergone pressure reduction will break loose and 'peel off'

Exfoliation domes

Large domed shaped structures usually composed of granite, formed by sheeting. when a rock forms deep underground from lots and lots of pressure.

Floodplain

a flat area along a river that forms from sediments deposited when the river overflows its banks

Frost wedging

The mechanical breakup of rock caused by the expansion of freezing water in cracks or crevices

gradient

slope of a land surface

Haboob

dust storm

headwaters

the source of a stream or river

hoodoo

a column of weathered and eccentrically shaped rock

hydrolysis

the weathering of feldspar into clay and ions with exposure to water

impermeable

not allowing water to flow through it

Mass wasting

the transfer of rock and soil downslope under the influence of gravity

meander scar

Dried up oxbow

mechanical weathering

rock breaks into smaller pieces (disintegration) without changing its composition

mesa

broad, flat-topped landform with steep sides; smaller than a plateau

middle aged Stream

a stream that flows down a medium slope or a medium valley, most of the rocks that cause waterfalls have been eroded away. the stream starts to erode more along its sides forming small meanders, while transportation dominates there is both erosion and deposition occurring

monument

butte that has shrunk to a pointed top

natural levee

raised river bank that parallels the channel that results when a river deposits its heavier sediment along the river bank as it floods into the floodplain

neck

the narrow strip of land separating two meander loops that will cut-off to form an oxbow

old age stream

a stream that is flowing over a very gentle slope and large discharge with primarily side-to-side erosion, many exaggerated meanders, and meander scars, a floodplain, oxbow lakes, delta, deposition dominates

oxbow

A meander that has been cut off from the river

oxidation

the weathering of metallic minerals in rock by interaction with humid air

permeability

Ability of rock or sediment to allow water to flow through it

Petroglyphs

Carved or scratched drawing of simple figures in rock. Carved through Desert Varnish.

point bar

a crescent-shaped accumulation of sand and gravel deposited on the inside of a meander

porosity

The percentage of the total volume of a rock or sediment that consists of open spaces.

river

water that flows downslope in a channel

meander

A large bend in a river

river mouth

the point where a river enters a lake or sea

River pothole

holes carved in a bedrock channel by sediment in a youthful river

river system

a river and its tributaries

root wedging

weathering of rock caused by the expansion of roots as they grow in cracks

sediment

the broken down bits of rock, categorized by size

spring

A flow of groundwater that emerges naturally at the ground surface

suspended load

the small sediment carried within the current of flowing water

talus slope

An accumulation of rock debris at the base of a cliff

tributary

A river that flows into a larger river

trunk stream

the primary river of a river system, the one that empties at the mouth

Unloading

in the lower rock layers occurs when the top layer of rock erodes away and therefore reduces the pressure on the lower layers causing sheeting, or separation of layers of rock.

velocity

another name for the speed of the current in a river

ventifact

any rock that is polished and shaped by wind abrasion

volcanic neck

middle part of volcano, hardened pipe

water table

the level below which the pores in the rock/sediment are saturated with groundwater.

waterfall

a vertical drop in a river that water flows over

weathering

The breaking down of rocks on the Earth's surface.

well

hole drilled into the ground to reach groundwater

youthful stream

a stream flowing down a steep slope with a straight channel, v-shaped valley, with some rapids and uneven drops, erosion dominates

zone of aeration

above the water table where pores in the rock/sediment are not filled with water

zone of saturation

below the water table where all the pores in the rock/sediment are filled with groundwater

stage

The height of the water in a river

saltation

The movement of sand or other sediments by short jumps, skipping, and bounces that is caused by wind or water

Sea Arch

an arch formed by wave erosion when caves on opposite sides of a headland unite

Sea Stack

column of rock remaining after the collapse of a sea arch

Aquiclude

Any. rock or sediment that water can not flow through EX: clay

infiltration

the process by which water on the ground surface enters the ground.