Erosion Transportation of sediments from one location to another

Review of Soil Formation Soil is formed by the physical and chemical weathering of rock. Soil is a mix of weathered rock and the remains of living organisms which plants can grow.

Layers of Soil Layers O thru C were made by weathering.

Types of Soil Residual Soil: soil that forms in place from the parent bedrock and remains there. Transported Soil: soil that was formed in one location and transported to another location by an agent of erosion.

What are the agents of erosion? Mass Movement (gravity) WaterAirGlaciers The most important FORCE of erosion is GRAVITY. The most important AGENT of erosion is WATER.

Mass Movement (Gravity) Gravity by itself can transport sediments. Evidence of erosion by mass movement: Rocks are Sharp-edged Rocks are Sharp-edged Sediments are Unsorted Sediments are Unsorted no limit in size of sediments no limit in size of sediments often causes “mass wasting” such as landslides and downhill creep often causes “mass wasting” such as landslides and downhill creep

Examples of Mass Movement Downhill Creep of Soil A living tree trunk bent by downhill creep. -Medina Seattle August 2004

Erosion by Water Water based on its velocity, can transport a variety of sediments. (see p. 6 of your reference table) sediments get rounded and polished. Sorting occurs. particles can be fairly large. deposition occurs where the water slows down. ex.: where the river widens or where it dumps into a large body of water. ex.: where the river widens or where it dumps into a large body of water. As water slows gradually, smaller and smaller particles drop out causing horizontal sorting

Relationship of Transported Particle Size to Water Velocity (p.6 of reference table)

What is Deposition? Deposition is the process by which sediments are released from an erosional agent.

Characteristics of Sediments and Rate of Deposition Many aspects of the sediments themselves affect how fast they will be deposited in the air or water environments. These factors include: Size Size Shape Shape Density Density Saturation of dissolved minerals Saturation of dissolved minerals

Factors of Depositon Size: The larger sediments settle out first when wind or running water slows down. Shape: The shape of a particle will determine how fast it will be deposited from wind or running water. The more rounded a sediment the faster it will settle out The more rounded a sediment the faster it will settle out The more flattened it is the greater its resistance. The more flattened it is the greater its resistance.

Factors of Depositon (continued ) Density: The higher the density of a sediment, the faster it will settle out or air or water. Saturation of Dissolved Minerals Evaporation, temperature changes or increases in the amount of dissolved minerals in a water body may result in a saturated condition. Evaporation, temperature changes or increases in the amount of dissolved minerals in a water body may result in a saturated condition. In this condition, the dissolved mineral(s) will settle out and crystallize (i.e.: limestone, dolostone) In this condition, the dissolved mineral(s) will settle out and crystallize (i.e.: limestone, dolostone)

Horizontal Sorting As water velocity begins to decrease, larger sediments begin to settle out followed by the smaller sediments.

Formation of Crossbeds and Graded Bedding Crossbeds are formed when several horizontal sorting events happen on top of each other such as in a river delta as the stream meanders back and forth. Graded bedding occurs when flooding occurs.

Vertical Sorting Vertical Sorting- caused by larger, rounder, denser sediments settling first.

Waves Wave action as seen under the waves

Evidence in Rock of Erosion by Water A V-shaped valley is evidence of water erosion.

Erosion by Wind sediments are rounded and have a frosty appearance (tiny pits from impacts of flying sand) sorting occurs. particles are small

Answer this question Taken from the August 2002 ES Regent Exam

Wind Erosion in a Desert

Erosion by a Glacier (Ice) Sediments are sharp-edged May have scratches or a polished side where they came in contact with the ground Deposits are unsorted and can be very large.

Glacial Till Deposition by a glacier is unsorted and unlayered.

Features associated with alpine glaciation Some of the other features associated with glacier erosion in alpine regions are cirques, horns, and arêtes cirqueshornsarêtescirqueshornsarêtes CirquesCirques are the bowl shaped depressions found at the head of glacial valleys. For most alpine glaciers, cirques are the areas in the alpine valleys where snow first accumulated and was modified into glacial ice. Cirques HornsHorns are pyramidal peaks that form when several cirques chisel a mountain from three or more sides. Horns ArêtesArêtes are the narrow serrated ridges found in glaciated alpine areas. Arêtes form when two opposing cirques back erode a mountain ridge. Arêtes

Evidence of Glacial Erosion Scratches (striations) in rock

Evidence of Glacial Erosion (continued) A U shaped valley results from glacial erosion. (Mt. Marcy) Another U-Shaped Valley in Alaska

Glacier Characteristics

Erratics Erratics are boulders that are transported a great distance from their place of origin by a glacier. boulders

Outwash Plain Outwash plainOutwash plain develops when there are a great number of meltwater streams depositing material ahead of the glacier Outwash plain

Kames Where sediment rich water flows into a crevasse or depression in the ice, a conical-shaped pile of sand and gravel, known as a kame, can form. Many kames are often found on or at the edge of moraines kame

Eskers Glaciers can also contain sinuous flows of meltwater that occur in ice tunnels at the base of the ice. The beds of these sub-surface glacial streams are composed of layers of sand and gravel. When the ice melts from around the meltwater tunnels, the beds of sand and gravel are deposited on the Earth's surface as long twisting ridges known as esker sandgraveleskersandgravelesker

Drumlins Another feature of continental glaciation are hill shaped deposits of till known as drumlins drumlins The streamline shape of these glacial features resembles a extended teaspoon laying bowl down. The gently sloping tapered end of the drumlin points in the general direction the glacier traveled.

Drumlins

Kettle Lakes When glaciers are rapidly retreating, numerous blocks of ice can become detached from the main body of the glacier. If glacial drift is then placed around the ice, a depression on the surface called a kettle hole can be created when the ice melts. Kettle holes are commonly found on moraine and outwash plain deposits. Large kettle holes that reach below the water table can form into lakes retreatingkettle holeretreatingkettle hole

Kettle Lakes Kettle Lakes, Northwest Territory, Canada

Comparison of Water and Glacial Erosion U shaped valley, evidence of a Glacier V shaped valley, evidence of a stream

Comparison of Water and Glacial Erosion Glaciers U shaped Valley U shaped Valley Sediments are Sediments areUnsortedUnlayered Kettle Lakes Kettle Lakes Kames Kames Drumlins Drumlins Scratches in underlying rock Scratches in underlying rockWater V shaped valley Sediments are Sorted Layered