Erosion and Deposition

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

*Turn to the back of your notes to copy the following:

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?

*Turn to the back of your notes to copy the following:

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