Water Erosion Chapter 9 Section 2

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

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

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 grooves gullies – formed after a rain as rills flow together streams – 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.