1. Earth’s Changing Surface
Water
Earth’s Changing Surface

2. Running Water
The major agent of the erosion that has shaped Earth’s land surface.

3. Runoff Water that moves over Earth’s surface.
Amount of runoff in an area depends on:
Amount of rain
Vegetation
Type of Soil
Shape of the land
How people use the land

4. Generally
More runoff, more erosion

5. The Course of a River
Runoff moves down hill and forms rills and gullies
Gullies join together to form a stream
Stream grow larger and combine with other streams and rivers called tributaries.

6. Rills and Gullies

7. Streams and Rivers
Stream – a channel along which water is continually flowing down a slope.

8. Tributary
Tributary – a stream or river that flows into a larger river.
Example: Wisconsin River is a tributary to the Mississippi

9. Erosion by Rivers
Waterfall – occur where a river meets an area of rock that is very hard and erodes very slowly.
The water then flows over softer rock downstream

11. Flood Plain The river usually flows over more gently sloping land.
The river spreads out and erodes the land, forming a wide river valley
Flood Plain – the flat, wide area of land along a river.

13. Meanders and Oxbow lakes
Meander – a loop like bend in the course of a river
Oxbow lake – a meander that has been cut off from the river.

15. Deposits by Rivers Deposition creates landforms!
Alluvial Fans
Deltas
It can also add soil to a river’s flood plain

16. Alluvial Fans
A wide, sloping deposit of sediment formed where a steam leaves a mountain range.

17. Delta
Sediment deposited where a river flows into an ocean or lake builds up a landform.

19. Deposition During Floods

20. The Course of a River

21. Groundwater Erosion
Groundwater – water that fills the cracks and spaces in underground soil and rock layers.
Can cause erosion through a process of chemical weathering.

22. Caves
The action of carbonic acid on limestone can result in deposition
Stalactite – deposits in caves that hang like an icicle from the roof of the cave.
Stalagmite – slow dripping builds up a cone-shape from the cave floor.