1. Water Erosion
Chapter 9
Section 2

2. Runoff and Erosion
Moving water is the major agent of the erosion that has shaped Earth’s land

3. Water Cycle Power source Condensation Precipitation Evaporation Runoff
Groundwater
Water Cycle
Runoff

4. Runoff and Erosion Runoff is water that moves over Earth’s surface
Five factors that influence amount of runoff
Amount of rain
Vegetation
Type of soil
Shape of the land
How people use the land
Generally, more runoff means more erosion

5. Runoff and Erosion
As water runoff travels it forms grooves in the soil
rills – tiny grooves
gullies – formed after a rain as
rills flow together
streams – formed as gullies flow
together. They rarely dry up

6. Runoff and Erosion River – a large stream
Tributary – a stream or river that feeds
into a larger stream or river

7. Runoff and Erosion Drainage basins or
watersheds are areas from where rivers and tributaries collect their water

8. Erosion by Rivers
V-shaped valleys – caused by fast flowing rivers that carve steep slopes along the sides

9. Erosion by Rivers
Waterfalls – where water flows over hard rock that erodes slowly, then flows over softer rock that erodes quickly

10. Erosion by Rivers
Rapids – areas of rough water where a river tumbles over hard rock.

11. Erosion by Rivers
Flood Plain – where a river slows down, spreads out and erodes the land forming a wide river valley

12. Characteristics
Steep sides
Mountainous or hilly regions
Rapidly flowing water
White water rapids and water falls
Curving stream
Gradual slope
Erodes sides
Less swiftly moving
Meanders
Flood plains
Very slow
Broad flat flood plain
Oxbow lakes

13. Erosion by Rivers
Meanders – bends in the river as it erodes softer rock on its bank
Oxbow Lakes – a meander that has been cut off from the main river

14. Deposits by Rivers
Alluvial fans – when a river comes off a mountain and widens, it slows down and deposits sediment as new soil

15. Deposits by Rivers
Deltas – When a river flows into a body of water, slows down and drops its sediment.

16. Groundwater Erosion
Groundwater – water that soaks into the ground. It fills in the spaces and cracks of soil and rock.
- can cause erosion through chemical weathering

17. Groundwater Erosion
Caves – water that mixes with CO2 forms a weak acid that can break down buried limestone and produce hollows
Sinkholes –
caused when
caves fall in

18. Groundwater Erosion
Carbonic acid and calcite can be deposited on cave roofs and floors to form stalactites, stalagmites, and columns.
stalactite
stalagmite
column

19. Groundwater Erosion
Karst Topography – an area where there are a lot of sinkholes due to the underground erosion of limestone.