Erosion and Deposition Pages D58-D64

Mass Wasting

The downhill movement of Earth’s material caused by gravity. Depends on how steep a slope is It can happen slowly, particle by particle, over the years. It can happen suddenly when a buildup of loosened particles can no longer be supported by material beneath. It can happen after a heavy rain, earthquake, or anytime

Deposition

The dropping off of particles These particles are called sediments. Changing the shape of the land. As materials are picked up and dropped off the land changes shape. Mountains wear down from steep pinnacles to low hills. Valleys widen, fill up with rock and soil, and become plains.

Wind

Easily picks up fine particles, like clay and sand The faster the wind is, the larger the size of the particles it can carry. As the wind slows down, it drops the sediment off The biggest, densest particles are dropped first.

Wind can blow sediment against rocks These rocks act like tiny sandblasters. They can dig into hillsides and polish stones. As the sand is dropped off, it can build into a dune. The dunes continue to change shape over time

Flowing Water

Can toss loose particles of rock around and carry them along as it flows downhill. The faster the water is moving, the bigger and denser the particles it carries can be Large particles are carried along by rolling, sliding, or bouncing along the bottom Smaller particles swirl along in the water or get dissolved in the water

The rocks being carried by the water slam into and chip away at rocks along the sides, the river bank. The particles are dropped off whenever the water slows down These dropped off particles form a mound or layer The flatter the stream or river is, the curvier it is

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What Causes Moving Water to Slow Down An obstacle could block the flow of water. A steep river could flow onto a flat plain. The water could flow into a big standing body of water, like a lake or ocean. In each of the above cases sediments are deposited when the water slows down and forms a mound or layer.

In which part of the river would deposition take place?

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Glaciers

Huge moving sheets of ice. Glaciers form when more snow falls in the winter than melts in the summer Over time the snow gets deeper and deeper As snow piles up, the weight of the snow on top squeezes the snow at the bottom into a solid mass of ice. The weight above makes the ice at the bottom like a super-thick syrup and the whole sheet of ice moves downhill

They move like huge, slow bulldozers and push loose rocks and soil out of their path Loose rocks and soil get pushed up in piles along the front and sides of the glacier Rocks get frozen back into the ice as it is moving These rocks can scrape against the land as it is moving Polishes rocks smooth They act like blades on a huge plow.

When glaciers melt The reach areas that are warm and begin to melt. The rocks that were frozen into it fall to the ground in a jumble known as a till. Some piles of till get smoothed out if a glacier flows over them called drumlines.

A deposit of many sizes of sediment from a glacier that collects in front or along the sides of a glacier is a moraine. Left behind in mounds or long ridges.

Forms ponds or lakes Chunks of ice get buried in the till When the ice chunks melt, the till above collapses forming a hole in the ground The holes fill up with water.

Or They scrape huge bowl shapes in the ground The bowls fill up with meltwater when the glacier melts The moraines act like dams, trapping the meltwater into lakes