EROSION DEPOSITION What is erosion Erosion is the

EROSION & DEPOSITION

What is erosion? -Erosion is the removal of rock particles and soil from an area -Erosion requires energy (usually supplied by gravity)

There are 4 distinct agents of erosion -Rivers/streams -Glaciers -Wind -Wave Action

Transport of Sediments in Streams -Sediment transport is dependent on 2 variables: -Velocity (speed) of water -Particle Size *Shape and density are of some importance

Particle Size Increasing Size -Rock Particles are categorized into 6 types: -Boulders -Cobbles -Pebbles -Sand -Silt -Clay *Dissolved minerals are also transported

Quantified Sediment Sizes

Sediment Transport Chart -In general, the chart shows that larger particles require an increased water velocity (speed) to be transported -If water velocity falls below that level, sediment is deposited on the bottom of the river

Water Velocity and Stream Morphology -Water velocity is not a constant along a river nor is it constant across a transect

Water Velocity and Stream Morphology -Because this is true, rivers have different channel shapes -In a straight line path, rivers are fastest in the middle, leaving a channel deepest in the center -As river water enters a curve, the faster water is on the outside causing more erosion and a greater depth

Stream Meanders -As water slows on the inside bend of a meander sediments are deposited in a process called deposition -Erosion takes place on the outside of a curve; particles are removed by the faster water -The meanders will look like this

Sorting of Sediments -Faster moving water removes smaller sediments -Therefore, a stream bottom will have larger particles on the bottom in faster moving water and smaller particles on the bottom in slower moving water -Streams result in sorted sediments based on water velocity

Streams Entering Lakes -The stream flow slows and the largest sediments are deposited first

Stream Valley Shape -As streams downcut through soil and bedrock, they create a V-shaped valley

Glaciers -Glaciers form when repeated snowfall accumulates in an area and forms into an ice pack that is able to flow

Types of Glaciers -For our purposes, there are 2 types of glaciers: -Continental (Ice sheet): Spans all or some of a continent -Valley (Alpine): Restricted to a valley

Glacial Presence in NYS -A massive glacier covered New York (most recently around 10, 000 years ago), and it is important to understand how it shaped landforms in the area

Glacial Weathering -Abrasion is the dominant form of weathering underneath a glacier -Rocks and other sediment are ground against bedrock as they are dragged overhead -Evidence: We find parallel grooves, called striations, in bedrock

Glacial Erosion -As glaciers erode a landscape, they leave evidence of having been there -Valleys take on a “U” shape

Finger Lakes -Glacial erosion can leave behind a variety of observable features -Finger Lakes are carved out of bedrock in the direction that the glacier moved

Drumlins -Elongated hills called drumlins are also found in areas that have undergone glaciation -The drumlins align with the direction of glacial movement

Erratics -Large boulders that do not match local bedrock type or are found in awkward elevations or places were likely transported there by a glacier

Eskers -Long, winding hills of sediment deposited by streams beneath a glacier -Sediment will be sorted and rounded

Kames -Rocky debris that is deposited in crevasses within a glacier to form a hill

Kettle Lakes -When large chunks of the glacier break off and are partially buried, they melt to form a kettle lake

Moraines -Moraines are long hills that are composed of material that a glacier has pushed or pulled along -Rocks in moraines are unsorted angular

Outwash Plain -An outwash plain is where many streams (or just a few) flow out of the glacier as it melts -The plain is relatively flat with sorted and rounded sediments due to abrasion in the streams

Cirques, Aretes, Horns -All features found in mountainous areas once covered by glaciers Horn: Sharp point at mountain peak Cirque: Bowl-shaped depression caused by abrasion -Arete: Sharp ridge carved out of the mountainside

Wind Erosion and Weathering -Abrasion is the dominant form of weathering in dry climates -Rocks become “sandblasted” and the particles are blown away

Wind Deposition -Sand other particles are deposited in dunes

Wave Erosion and Weathering -Abrasion is the dominant form of weathering -Particles are washed on shore, swept back out, and gradually move in the direction of the current

Long Shore Current -Long shore currents flow parallel to the beach -This steadily drags sediments along the shore in what is called long shore drift

Mass Movement -The final, though less substantial type of erosion is called mass movement -Mass movement is the sliding of any rock material or soil downhill as a result of gravity -Some mass movement is slow, and some is sudden

Landslide -Landslide is a commonly used for the movement of a mass of bedrock or loose soil and rock down the slope of a hill, mountain or cliff http: //www. youtube. com/watch? v=23 NZTzpw 6 c. Y

Creep -Slow, imperceptible movement of soil down a slope

Slump -Blocks of land that have tilted and moved downhill along a surface that curves into the slope

Mudslides/Flows -Rapid movement of Earth saturated with water