Download
1 / 12
120 likes | 258 Views
Topic10: Deposition. Deposition = the process by which sediments are released, settled from or dropped from an erosional system. **Deposition usually occurs when the velocity or speed of any erosional system decreases or stops moving** ex: A stream slowing down. Rate of Deposition.
E N D
Topic10:Deposition Deposition = the process by which sediments are released, settled from or dropped from an erosional system. **Deposition usually occurs when the velocity or speed of any erosional system decreases or stops moving** ex: A stream slowing down
Rate of Deposition • The faster a stream flows, the larger the size sediments it can carry. ESRT chart pg. 6 • Larger sediments settle out faster, they tend to be heavier and sink faster • The more rounded a sediment, the faster it will settle • The larger the density, the faster it will settle
Sorting of sediments and deposition • When a mixture of sediment sizes in water settle out rapidly, a horizontal bed or layer develops. The sediment size will decrease from the bottom to the top. This is called graded bedding. • In a delta, the larger, denser and more rounded sediments will settle first.
Glacial and Mass Movement Deposits • In a glacier and mass movements, sediments of all sizes, shapes and densities are deposited together. This will produce a unsorted un-layered deposit
Dynamic Equilibrium if an Erosional System • Since all sediments picked up by the stream during erosion must eventually be deposited, the system is said to be in dynamic equilibrium. • Meaning: Rate of erosion = Rate of deposition
Features produced by deposition of a Stream ~ In a stream itself, deposition occurs on the inside of meanders, where the velocity is low. ~ When a stream overflows, sediments form levees at the edge of the river. Sediments also spread out in the floodplain ~ If the stream changes its path, you can have a meander or bend that is cut off, creating a curved lake (oxbow lake)
Features produced by deposition of a Glacier ~ At the end of a glacier, sediments are dropped in unsorted sheets called a moraine. ~ If sediment deposits at the bottom of a glacier, it tends to be a low, long, narrow, streamlined oval mound. This is called a drumlin. ~ When a block of ice is left behind and melts it forms a depression called a kettle. When they get filled with water, it is called a kettle lake. ~ As a glacier melts, running water will produce a sorted deposit called a outwash plain (broad delta like feature).
Deposition on Coastlines by waves and currents ~Wave movement towards the shore builds up sediment at the coastline, called a beach. ~ If a sandbar rises above sea level, vegetation can stabilize and grow, creating a barrier island.
Deposition by Mass Movement ~ The most recognizable feature of mass movement is a pile of sediment often found at the base of cliffs.
Deposition by Wind • When wind slows down or stops blowing, sediments are dropped-but these particles are typically smaller than sand. • Particles smaller than sand are usually categorized as dust. Much of the dust is deposited over a large expansive area. • Sand particles are deposited in layers or mounds called sand dunes. Sand dunes typically have a gentle slope on the windward side and a steep slope on the leeward side. They will “migrate” in the direction of the wind creating layers of sloping sorted sediment that is cross-bedded.
