Chapters 7-9 . Weathering Erosion Deposition. Chapter 7: Weathering and Soil Weathering: surface processes that work to break down rock
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1) Mechanical weathering: breaks apart rocks without changing their chemical composition (without changing the type of rock)
2) Chemical weathering: the reaction of water, air, and other substances with the minerals in rocks which changes the chemical composition of the rocks
Find 3 ways to move the soil from one side of the plate to the other.
You may not touch the soil with your hands! But, you can touch the plate.
Do not spill!
Erosion: process that wears away surface material and moves them from one place to another
Deposition: the dropping of sediments that occur when an agent of erosion looses its energy of motion and is no longer able to carry the load
What causes erosion and deposition?
- Gravity! What is gravity? The force of attraction that exists between all objects
- Since Earth is so large, all objects are attracted to it.
- The Earth is the source of all our gravity.
- Any loose material will be pulled down a slope (hill), due to gravity.
- When gravity alone causes material to slide down a slope this is called mass movement.
2) Creep: sediments slowly inch their way down a hill…most common in freezing areas.
Rockfalls (tumble) and Rock Slides: when large rocks break loose and tumble down a hill…can be very destructive!
4) Mudflows: a thick mixture of sediment and water flowing down a slope…dry areas with thick layers of sediment that suddenly get really wet from rain…
How can you prevent these problems?
We can try all we want to avoid erosion and deposition problems, but in the long run…gravity will still be too powerful!
IE – video of mudslide…
Transporting and Scouring – as glaciers move forward over land, they can transport huge volumes of sediment and rock. The rock leaves marks behind as it moves.
Moraine Deposits – large ridges of rocks and soil deposited by a glacier when it stops moving forward.
But…strong wind with dry soil…nothing will stop erosion by wind!
Creates a variety of land forms…
Loess: wind deposits of fine- grained sediment…packed together creates a thick unlayered yellowed- brown colored deposit
What happens when wind blows sediment against an obstacle? = dune!
Dunes: created when sediment settles behind an obstacle
Dunes can be moved as sand is lifted and deposited downwind…(picture )
Overall…Erosion and Deposition constantly shape and reshape the land!
Deposition of Surface Water