1. Erosion and Deposition
Science: 7th grade Ch.8
8th grade Ch.

2. Review: What is weathering?
The process that breaks down rock and other substances on the Earth’s surface

3. Erosion
The process by which natural forces move weathered rock and soil from one place to another.
Gravity
Running water
Glaciers
Waves
wind

4. Example of Erosion
Heavy rains washing out soil and gravel from a drive way

5. Sediment
Material moved by erosion is called sediment

6. Deposition
Deposition occurs where the agents of erosion lay down sediment
Changes the shape of the land

7. Analogy
Tearing down a lego tower and taking the individual legos to another location.
Use the legos to build something else.

8. Gravity The force that moves rock and other materials downhill
Gravity causes mass movement
Landslides
Mudslides
Slump
Creep

9. Landslide
Occurs when rock and soil slide quickly down a steep slope

11. Mudslide Rapid downhill movement of a mixture of water, rock and soil
Often occur in dry areas after a heavy amount of rain
Can be a catastrophic event

14. Slump
A mass of soil and rock suddenly slips down a slope in one large mass
Often occurs when the base of the mass is soaked with water

16. Creep The very slow downhill movement of rock and soil
Happens very slowly
Results from the freezing and thawing of water in cracked layers of rock beneath the soil

19. Water Erosion

20. Runoff
Moving water that runs over the Earth’s surface that causes erosion
Sediment is carried with the running water

21. Runoff

22. Factors Affecting Runoff
Amount of rain
Vegetation (grasses, shrubs and trees)
Type of soil
Shape of the land
How people use the land (concrete or soil?)

23. Gully
A large groove, or channel, in the soil that carries runoff after a rainstorm
As water flows, rocks and soil are carried with it
Only flows after it rains

24. Gully

25. Stream Gullies join together to form a stream
– a channel that has water continually flowing down a slope
Rarely dry up
Also called a brook or creek

26. Stream

27. River
As streams flow together, they form larger and larger bodies of flowing water called a river

28. River
Stream

29. Tributary A tributary occurs when one stream flows into another
Creek  River
River  River

30. River
Tributary
Stream

31. Erosion by Rivers Rivers often form on deep mountain slopes
Rapids are formed where water tumbles over rocks
Waterfalls occur due to erosion – rock is worn away

32. Stream Processes and Floodplain Development

36. Flood Plain The flat, wide area of land along a river
A river covers the flood plain when it floods

38. Meander When the river flows through easily eroded rock or sediment
A loop-like bend in the course of a river
Erosion takes place along the banks of the meander
Gets wider and wider, more curvy

39. River
Tributary
Stream
Meander

40. Oxbow Lake A meander that has been cut off from the river.
An oxbow lake may form when a river floods.
Sediments dam up the ends of a meander.

42. Oxbow Lakes

43. Oxbow Lake

44. Deposition As water moves, it carries sediment with it.
Anytime the water slows down, fine particles fall to the river’s bed.
Larger stones quit rolling and sliding.
Deposition creates landforms such as alluvial fans and deltas.
It can also add soil to a river’s flood plain.

48. Alluvial Fan Where a stream flows out of a steep, narrow valley
The water slows down and sediments are deposited.
A wide, sloping deposit of sediment is formed where a stream leaves a mountain range.

50. Deltas
Sediments deposited where a river flows into an ocean or lake and builds up a landform called a delta.

54. Assignment: Finish the vocabulary flash cards – turn in today!
Color code the river diagram in your notes – turn in today!
Complete the weathering and erosion worksheet – due tomorrow but get it done today!