Water Erosion

Chapter 9

Section 2

Runoff and Erosion

• Moving water is the major agent of the erosion that has shaped Earth’s land

Runoff

Groundwater

Runoff

Condensation

Precipitation

Power source

Water Cycle

Evaporation

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

Runoff and Erosion

• As water runoff travels it forms grooves in the soil

rills – tiny groovesgullies – formed after a rain as

rills flow togetherstreams – formed as gullies flow

together. They rarely dry up

Runoff and Erosion

River – a large stream

Tributary – a stream or river that feeds

into a larger stream or river

Runoff and Erosion

• Drainage basins or

watersheds are areas from where rivers and tributaries collect their water

Erosion by Rivers

• V-shaped valleys – caused by fast flowing rivers that carve steep slopes along the sides

Erosion by Rivers

• Waterfalls – where water flows over hard rock that erodes slowly, then flows over softer rock that erodes quickly

Erosion by Rivers

• Rapids – areas of rough water where a river tumbles over hard rock.

Erosion by Rivers

• Flood Plain – where a river slows down, spreads out and erodes the land forming a wide river valley

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

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

Deposits by Rivers

• Alluvial fans – when a river comes off a mountain and widens, it slows down and deposits sediment as new soil

Deposits by Rivers

• Deltas – When a river flows into a body of water, slows down and drops its sediment.

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

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

Groundwater Erosion

• Carbonic acid and calcite can be deposited on cave roofs and floors to form stalactites, stalagmites, and columns.

stalactite

stalagmite

column

Groundwater Erosion

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