Erosion

Downcutting

downcutting is a geological process that deepens the channel of a stream or valley by removing material from the stream's bed or the valley's floor.

Components of erosion

1. an agent of erosion, such as a stream, glacier, wave, current, wind, or human activity 2. the sediments being moved 3. a driving force *the driving force for most types of erosion comes from gravity*

Q: A pebble is being transported on a stream by rolling. How does the velocity of the pebble compare to the velocity of the stream? A. The pebble is moving more slowly than the stream. B. The pebble is moving more quickly than the stream. C. The pebble is moving at the same velocity as the stream.

A

Q: The area drained by a river and its tributaries is called its A. watershed B. mouth C. source D. divide

A

Q: The primary force responsible for most of the transportation of rock material on the surface of Earth is A. gravity B. wind C. running water D. glaciers

A

Q: Which erosional force acts alone to produce avalanches and landslides? A. gravity B. running water C. winds D. sea waves

A

Q: Which material would most easily be carried in suspension by a slow-moving stream? A. clay B. sand C. silt D. pebbles

A

V-shaped valley

A V-shaped valley is a narrow valley with steeply sloped sides that appear similar to the letter "V" from a cross-section. They are formed by strong streams, which over time have cut down into the rock through a process called downcutting.

Q: By which processes are rocks broken up and moved to different locations? A. evaporation and condensation B. weathering and erosion C. burial and cementation D. compaction and transportation

B

Q: Much of the erosion by wind is caused by A. pushing sediments over cliffs B. abrasion by blowing sand C. deposition of silt and clay in dunes D. scraping and gouging deep depressions in Earth's surface

B

Q: The increase of dissolved materials in the ocean is primarily the result of the A. abrasion of the ocean floor B. transporting of material by rivers C. melting of continental glaciers D. deposition of materials by ground water

B

Q: Wind erosion is most active in regions that have A. a hot climate B. much loose sediment C. weak or non-resistant bedrock D. bedrock exposed to the atmosphere

B

Q:The best evidence that erosion has taken place would be provided by A. deep soil formed in place on a hillside B. sediment observed at the bottom of a cliff C. folded rock layers observed on a mountain D. faulted rock layers observed on a plateau

B

Q: Which agent probably contributes most to the general wearing down of Earth's surface? A. wind B. glaciers C. running water D. ocean waves and currents

C

Two main aspects of wind erosion

Deflation and sandblasting (abrasion)

Deflation process

Deflation takes place in areas with small, loose sediments exposed to the atmosphere. Winds blow away the loose sediments, lowering the land surface. The lowering of the land surface can continue until there are no longer any small solid sediments exposed to the winds.

Fan-shaped delta

Deltas are wetlands that form as rivers empty their water and sediment into another larger body of water.

Sandblasting process

Sandblasting occurs when winds blow sand or silt grains against rocks and other objects. The pelting by the grains can erode, or abrade rocks.

Levees

Sediment mounds (piles) that are along the banks of a stream

Q: Describe the relationship between mass movement and gravity.

The downhill movement of rock or sediment without being carried by water, wind, or ice is called mass movement and it starts going down because of gravity.

Mass Movement (mass wasting)

The downhill movement of rock or sediment without being carried by water, wind, or ice. Material can slide, flow, or fall to its resting place.

Mouth (of a stream)

The end of a stream

Gradient

The slope of the stream

Erosion

Weathering of rock produces particles that are transported as sediments. Erosion is the transportation of weathered sediments.

Floodplain

a flat area of land that is prone to flooding. It is usually next to a river or stream.

Glacier

a naturally formed mass of ice and snow that moves downhill on land under the influence of gravity.

Tributary

a smaller stream that flows into a larger stream.

Agents of erosion

a stream, glacier, wave, current, wind, or human activity

Channel

a waterway between two land masses that are close to each other.

Watershed (drainage area)

an area of land drained by a stream.

Stream

running water that is confined to a channel.

Meanders

Bends or turns in a stream

Finger lakes

Bodies of water in U-shaped valleys carved by glaciers

Q: How are dissolved particles of sediment carried in a river? A. by bouncing and rolling B. by precipitation C. in solution D. in suspension

C

Q: The velocity of a stream at a particular location is controlled mainly by the... A. elevation of the stream at the location B. distance of the location from the source C. slope of the stream channel at the location D. amount of sediments carried at the location

C

Q: Two streams, A and B, carry the same volume of water, but stream A has a greater velocity. The most likely cause of this greater velocity would be that stream A A. has more tributaries B. has a wider stream bed C. flows down a steeper slope D. travels over less resistant bedrock

C

Q: What is the most important reason that sediments at beaches are usually rounded and smooth? A. The water dissolves the edges of the sediments. B. The high heat at beaches partly melts the sediments. C. The moving water causes sediments to abrade against each other. D. The coastal storms move rounded sediments toward the beach from deep ocean areas

C

Q: Which statement best describes a stream with a steep gradient? A. It flows slowly, producing a V-shaped valley. B. It flows slowly, producing a U-shaped valley. C. It flows rapidly, producing a V-shaped valley. D. It flows rapidly, producing a U-shaped valley.

C

U-shaped valley

A U-shaped valley is formed by the process of glaciation (being covered by glaciers). It has a U shape, with steep, straight sides and a flat bottom. Glaciated valleys are formed when a glacier travels across and down a slope, carving the valley by the action of friction.

Erratics

A rock of unspecified shape and size (different), transported a significant distance from its origin by a glacier or iceberg and deposited by melting of the ice.

Q: The composition of sediments on Earth's surface usually is quite different from the composition of the underlying bedrock. This observation suggests that most A. bedrock is formed from sediments B. bedrock is reduced by weathering C. sediments are formed from local bedrock D. sediments are transported

D

Q: Which agent of erosion formed the long U-shaped valleys now occupied by the Finger Lakes in central New York State? A. running water B. ocean currents C. wind D. glacial ice

D

Stream abrasion

Stream abrasion is the process in which sediment rolls across the bottom of the stream bed which smooths the sediment because of the constant friction. The individual particles of sediment also collide as they are transported, breaking them down into smaller particles.

Discharge

The volume of water in the stream

Glacial grooves and glacial parallel scratches

grooves/ scratches that cut into the bedrock by gravel/sediments and rocks carried by glacial ice and meltwater.

Stream channel shape

the shape of the bed of rock or loose materials that confine the stream.