geo test two new

Weathering

The breakdown of rocks into smaller pieces or altered materials.

Erosion

The movement of weathered rock and sediment.

Mechanical weathering

Physical breaking of rock into smaller pieces without changing its composition.

Chemical weathering

Breakdown of rock that changes its chemical composition.

Environment promoting chemical weathering

Places with liquid water.

Environment promoting mechanical weathering

Places with little or no liquid water, as emphasized in the review slides.

Frost wedging

Water enters rock cracks, freezes, expands, and pries the rock apart.

Biological activity

Plant roots grow into cracks and pry rocks apart.

Salt crystallization

Salty water enters cracks; growing salt crystals push the rock apart.

Exfoliation joints

Rock cracks and peels apart as pressure on it decreases.

Dissolution

Water completely dissolves rock material, carrying it away in solution.

Leaching

Some rock material dissolves and is removed, leaving other material behind.

Oxidation

Iron in rock reacts chemically and rusts.

Differential weathering

Different rock types weather and erode at different rates.

Shale

Weak rock that is vulnerable to mechanical weathering.

Limestone

Strong rock that dissolves in water but resists weathering in dry deserts.

Sandstone

Very strong rock that resists most weathering processes.

Sandstone cliffs vs. shale slopes

Resistant sandstone forms steep cliffs; weaker shale weathers into gentler slopes.

Joints in rock

Fractures that guide where weathering and erosion occur.

Rock fins

Thin walls of rock created as erosion follows joints.

Arches

Openings formed when the undersides of rock fins weather and break away.

Hoodoo

A tall, narrow pillar of rock left behind by weathering and erosion of weakened rock fins.

Steps of arch and hoodoo formation

Hard rock overlies softer rock; joints guide erosion; fins form; fins become arches or hoodoos.

Bed load

Sediment that rolls along a streambed.

Suspended load

Sediment particles carried while floating in stream water.

Dissolved load

Dissolved ions carried in stream water.

Straight stream channel

A steep stream that erodes rapidly downward.

Meandering stream channel

A winding stream channel commonly found on flatter terrain.

Braided stream channel

A stream that splits into channels when carrying too much sediment.

Rectangular drainage pattern

Stream network associated with fractured bedrock.

Radial drainage pattern

Streams flowing outward from a central high point such as a volcano.

Trellis drainage pattern

Streams arranged along long ridges and valleys in folded mountains.

Dendritic drainage pattern

Branching streams associated with horizontal rock layers or granite.

Parallel drainage pattern

Streams flowing roughly side by side in the same direction, often down a uniform slope.

Groundwater

Water that infiltrates the ground and fills spaces between rock particles.

Porosity

The percentage of a rock made up of holes or pore spaces.

Permeability

How easily fluid can flow through rock.

Zone of saturation

Underground region where all rock pore spaces are filled with water.

Water table

Boundary between air-filled rock pores above and water-filled pores below.

Cave formation

Usually occurs when groundwater dissolves limestone along fractures.

Mesa Verde caves

Form when water dissolves the mineral cement holding sandstone grains together.

Sinkhole

A depression caused when the roof of a large underground cave collapses.

Precipitation of calcite

Dissolved ions crystallize into solid calcite as dripping cave water evaporates.

Stalactite

Calcite deposit that forms hanging from a cave ceiling.

Stalagmite

Calcite deposit that grows upward from a cave floor.

Alpine glacier

A glacier that flows down mountain valleys.

Continental glacier

A giant ice sheet that spreads outward in several directions.

Glacial valley

A U-shaped valley carved by a glacier.

Stream valley

A V-shaped valley carved by a stream.

Till

Unsorted sediment of many sizes transported and deposited by glacial ice.

Loess

Very fine-grained sediment carried by wind after a glacier melts.

Glacial erratic

A large boulder transported by glacial ice.

Moraine

A ridge of glacial till showing how far a glacier reached.

Glacial striations

Scratches on rock that reveal the direction a glacier flowed.

Wave-cut terraces

Wave-eroded ledges from lower sea levels that indicate water stored in glaciers.

Sandstone cliffs vs. shale slopes

Resistant sandstone forms steep cliffs; weaker shale weathers into gentler slopes.

Parallel drainage pattern

Streams flowing roughly side by side in the same direction, often down a uniform slope.

Mesa Verde caves

Form when water dissolves the mineral cement holding sandstone grains together.

Sinkhole

A depression caused when the roof of a large underground cave collapses.