EROSION

What is Erosion? The transport of sediments from one location to another

Erosion of Montauk Point Lighthouse 1838 1990 200 feet of land lost in 200 years

EROSION IS DRIVEN BY THE FORCE OF GRAVITY

What are the agents of erosion?

Gravity Landslides, Avalanches

Avalanche

Gravity Fallen rocks are sharp and angular

Landslide

Wind Erosion

Wind Erosion occurs primarily in arid climates

Wind Erosion: When the wind picks up and carries away loose particles it is known as deflation. Abrasion exposed rock is worn away by wind blowing particles.

Wind Erosion Ventifact: a loose rock particle (too heavy to be carried by the wind) that are abraded by wind blown particles.

Wind Erosion

Factors Affecting Wind Erosion Speed -The faster the wind blows  the larger the particles it can transport Particle size -The larger the particles the greater the abrasion of exposed surfaces Length of time -The longer the wind blows  the more wind erosion

Desert Sandstorm

Glaciers ICE

Glaciers

exposed rock is worn away by smaller particles carried by the ice. Glaciers erode the surfaces over which they move by: Abrasion: exposed rock is worn away by smaller particles carried by the ice. 2. Plucking: loosening rocks, picking them up and carrying them away

Small sediments (such as clay and silt) carried by glaciers smooth and polish the rock surface below.

Larger sediments carried by glacier scratch and striate the rock surface below.

Glaciers create parallel striations in the bedrock. Direction of glacial movement is indicated by striations

Polished and Striated Bedrock

Glacial erratics are large rocks that have been transported by glacial ice without being broken into pieces

Running Water Streams, Rivers, Oceans

Running water is the primary agent of erosion!!! Water affects more of the Earth’s surface than any other agent of erosion.

Running water: Rounds and smoothes the rock Makes the rock smaller because jagged edges are broken off due to abrasion.

Each agent of erosion produces its own characteristic shape and texture in rocks.

Stream Basics Stream: any body of running water moving downhill due to gravity in a narrow channel Discharge: the volume of water in the stream at any given location during a specific amount of time. Stream Bed: the bottom of the stream channel and each side is known as the stream bank. Stream source: area where streams begin, usually in mountains or hills where rain water collects. Stream mouth: the place where a stream ends up – usually in a lake, sea or ocean. Stream gradient: the change in elevation from a stream’s source to its mouth.

The velocity of a stream depends on… Stream Discharge -The more water in the stream, the faster the stream will flow

Gradient: the steepness of the slope down which the stream is flowing. -The more of a hill there is the faster the water will flow.

Flat gradient = slow moving water Merrill ES Snyder Feather Hesser Flat gradient = slow moving water

Steeper slope = faster moving water

Particle Size The faster the stream moves, the bigger the particles it can transport.

Relationship of Transported Particle Size to Water Velocity R.T. pg. 6 Relationship of Transported Particle Size to Water Velocity ESRT

What happens to the size of the particle What happens to the size of the particle the stream can carry as the velocity of the stream increases? -The particle size increases. What happens to the size of the particle

The minimum velocity needed to carry a pebble is: 90 cm/sec

WHAT IS THE MINIMUM VELOCITY NEEDED TO CARRY A BOULDER? 325 cm/sec

Boulder What is the largest size particle that can be carried by a stream flowing 400 cm/sec? Boulder

If a stream is flowing 150 cm/sec, what is the largest size sediment it can carry? Pebbles

Name all of the sediments a stream can carry if it is flowing 50 cm/sec? Clay, silt

PARTICLES ARE CARRIED IN SEVERAL WAYS DEPENDING ON THEIR SIZE EROSION BY WATER:

Four ways streams transport materials: Solution: sediments are dissolved in water (salt ions)

2. Suspension: sediments are held in the middle of the stream but not dissolved. (clay, silt, sand)

3. SaltationRolled, bounced, or dragged along stream bed (pebbles, cobbles, boulders)

Floatation Some sediments float on the surface of the water.

Smaller sediments are dissolved or are suspended Larger sediments are rolled or dragged on bottom

The fastest flowing water in the stream is the area with the least friction. Friction from air Friction Friction No Friction from side from side Friction from bottom