Earth Science: Streams, Groundwater, Glaciers, and Deserts

Stream direction

Streams move water from higher elevations to lower elevations.

Headwaters

The beginning of a stream; steep slopes, fast-moving water, mostly erosion.

Trunk Stream

The main river channel where transportation of sediment occurs.

Mouth

Where a river enters a lake or ocean; deposition dominates.

Watershed

The land area drained by one river system.

Divide

A high area separating drainage basins.

Tributary

A smaller stream flowing into a larger stream.

Stream Erosion Processes

Streams erode by hydraulic action, abrasion, and dissolution.

Velocity vs. Erosion

Fast-moving water erodes more than slow water.

Dissolved Load

Invisible minerals dissolved in stream water.

Suspended Load

Fine sediment, such as clay and silt, suspended in water.

Bed Load

Sand, gravel, and pebbles that roll or bounce along the bottom.

Capacity

The total amount of sediment a stream can transport.

Competence

The largest particle size a stream can move.

Stream Velocity and Sediment Load

Fast streams have greater capacity and competence.

Deposition Trigger

Stream deposition occurs when water velocity decreases.

Deposition Landforms

Creates deltas, alluvial fans, floodplains, and sand bars.

Cut Bank

The outside bend of a meandering stream where erosion occurs.

Point Bar

The inside bend of a meandering stream where deposition occurs.

Meander Evolution

Meander → cutoff → oxbow lake over time.

Flooding Cause

Occurs when stream discharge exceeds channel capacity.

Urbanization and Flooding

Increases flooding because pavement prevents water infiltration.

Flood Control Methods

Levees, dams, floodwalls, and channelization.

Groundwater Storage

Stored underground in pore spaces and rock fractures.

Porosity

The amount of empty space in a rock or sediment.

Permeability

The ability of water to flow through a rock or sediment.

Clay Porosity and Permeability

High porosity but low permeability.

Gravel Permeability

High permeability.

Water Table

The upper surface of groundwater.

Aquifer

A rock or sediment layer that stores and transmits groundwater.

Good Aquifer Materials

Sand, gravel, and sandstone.

Poor Aquifer Materials

Clay and shale.

Cone of Depression

A depression in the water table formed by pumping groundwater.

Overpumping Consequences

Lower water table, drying wells, and land subsidence.

Artesian Well

Water rises under pressure from a confined aquifer.

Spring

A place where groundwater naturally reaches the surface.

Karst Topography

Landscape formed in limestone, featuring sinkholes, caves, and underground streams.

Stalactites

Cave features that hang from the ceiling.

Stalagmites

Cave features that grow up from the ground.

Groundwater Problems

Saltwater intrusion, contamination, overpumping, and subsidence.

Glacier Formation

Snow accumulates, pressure changes it to ice, and gravity causes movement.

Alpine Glacier

A mountain glacier that moves through valleys.

Continental Glacier

A huge ice sheet covering vast continental areas.

Glacial Erosion Processes

Plucking (pulling rocks) and abrasion (scraping smooth rock surfaces).

Cirque

A bowl-shaped depression at the beginning of a glacier.

Arête

A sharp ridge forming between glaciers.

Horn

A sharp peak formed by glaciers, such as the Matterhorn.

U-shaped Valley

A wide valley with a flat bottom and steep walls.

Moraine

A pile of unsorted glacial sediment.

Drumlin

A football-shaped hill indicating the direction of ice movement.

Esker

A long winding ridge created by streams beneath a glacier.

Kettle Lake

A lake formed when a buried block of ice melts.

Outwash Plain

Sorted sediment deposited by glacial meltwater.

Ice Age Causes

Orbital changes, solar variation, atmospheric composition, and plate tectonics.

Desert Rain Limit

Receives less than 25 cm (10 inches) of rain annually.

Desert Formations Causes

Subtropical highs, rain shadows, continental interiors, and cold ocean currents.

Deflation

Wind erosion that removes loose sediment.

Wind Abrasion

Wind erosion involving the sandblasting of rocks.

Desert Pavement

A surface covered with pebbles after fine particles are removed.

Ventifacts

Rocks polished and shaped by wind.

Playa

A dry lake bed in a desert.

Pediment

A gentle rock slope at the base of a mountain.

Alluvial Fan

A fan-shaped sediment deposit often formed after flash floods.

Sand Dune Requirements

Requires wind, a sand supply, and an obstacle.

Sand Dune Types

Barchan, transverse, longitudinal, parabolic, and star dunes.

Loess

Wind-blown silt that forms highly fertile soil.

Desert Weathering Type

Mostly mechanical weathering driven by temperature changes.

Desert Flash Floods

Common due to little vegetation and hard ground preventing infiltration.