III Depositionthe process by which sediments are released

III. Deposition-the process by which sediments are released, settled from or dropped from an erosional system. It occurs when the velocity or speed of an erosional agent slows down.

A. Factors Affecting Deposition 1. Velocity of the Transporting Agent. a. The faster the transporting agent, b. the larger the particles it can carr b. As the velocity decreases, the sediments are deposited, larger on the bottom, smaller on top. c. The smallest particles tend to remain in suspension for a long time.

2. Shape of the sediment Settling Rate a. Rounder particles(less surface area) b. settle faster than flatter particles c. in water. b.

3. Density of the sediment. a. Denser particles will settle faster b. than less dense particles. Settling Rate b. Density

B. Depositional Features 1. From Gravity: a. Talus conesediment that is found at the base of a hill or mountain.

2. From Running Water and Wave Action a. Sandbars-a build-up of sediment by wave action

b. Deposition takes place on the side of the groin that the long-shore current is coming from. t n o L h s g e r o n e rr cu Sand is trapped by the jetty(groin).

c. Delta: fan-shaped deposit of sediment at the mouth of a river. Nile River Delta

d. Sediment deposits are sorted. Horizontal Sortingoccurs when a stream enters a lake; as the stream velocity decreases, the larger, rounder, and high density sediments are deposited near the mouth of the stream.

Horizontal Sorting

Vertical Sorting or Graded Beddingresults when a sediment-laden current slows, particles are deposited.

3. From Wind a. Sand Dunes-the gentle slope faces the direction the wind comes from. d n i w

Draw a sand dune:

b. Deposits are sorted sediments, as the wind slows, the larger sediments are on the bottom, smaller on top. c. Cross-beddingdiagonal sand deposits caused by varying wind direction. Checkerboard Mesa, Zion National Park

4. From Glaciers a. Till(drift)-unsorted sediments b. deposited by the glacier. Moraine-till found along the sides or leading edge of the glacier.

b. Drumlins-elongated hills sculpted by a glacier’s retreat; they indicate the direction of flow. N S

c. Eskers-are long, winding ridges of sand gravel typically oriented parallel to ice flow. They were deposited by glacial melt water, streams, flowing in channels or tunnels beneath the ice.

d. Kames-mounds or hills are created when drift fills a hole in a glacier. When the glacier recedes the mound is left behind.

e. Kettle Lakes-formed when large blocks of ice break from the face of the glacier and are buried in sediment. When these blocks melt, they leave circular depressions.

f. Erratics-large boulders that were. deposited when the glacier melted. NYC-Central Park

g. Outwash Plain-melt water that washes out from under the glacier carrying sediments. Sorting will occur with a decrease in velocity of the water.