Topic 9 Deposition

Regents Earth Science

deposition Is the “dropping” of transported materials Or the processes by which transported materials

are left in new locations

Factors Affecting Deposition

Particle size Larger particles settle more quickly than smaller

particles (if they have the same shape and density) Colloids remain suspended indefinitely

Particle Size

Settl

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Particle Size

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Particle Shape Particles of the same size and maximum diameter

will settle out in this order: round, oval, flat The more spherical the particle, the faster the

settling rate. As flatness increases, settling time increases.

Remember: A short time is a high rate!

Particle density The denser the particle, the faster it will settle in

particles that have the same size and shape.

The rate at which particles are deposited by a stream is least affected by

1. size and shape of the particles 2. velocity of the stream 3. the stream’s elevation above sea level 4. density of the particles

A mixture of sand, clay, pebbles, and silt, of uniform shape and density, is dropped from a boat into a calm lake. Which material most likely would reach the bottom of the lake first?

1. sand 2. pebbles 3. clay 4. silt

sorting the separation of particles during deposition

In sediments of mixed sizes, shapes, and densities

Roundest, largest, and densest particles will be at the bottom of each layer.

Smallest, flattest, and least dense will be at the top of each layer.

Vertical sorting Sorting from top to bottom throughout a layer

Graded bedding Layers of sediment that are each vertically sorted Usually occurs in shallow, quiet bodies of water or

in the ocean Degree of sorting is usually greater in the bottom

layer than in the top layer

Process of forming graded beds

Graded bedding

Horizontal sorting The sorting of sediments into layers in which the

particles are sorted horizontally, ranging from largest to smallest in the direction of travel of the transporting agent

Horizontal sorting

delta A deposit formed at the mouth of a river as it

empties into a quiet body of water Named for the Greek letter delta

QuickTime™ and aCinepak decompressor

are needed to see this picture.

Nile Delta

Mississippi Delta

Alluvial fan A deposit of sediment formed where the velocity of a river slows as it

flows out of the mountains onto the flatland Also called a land delta

Sediments deposited by water are well sorted (either vertically or horizontally) rounded smooth may show graded bedding