Earth’s Changing Surface Water Earth’s Changing Surface

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

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

Generally More runoff, more erosion

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.

Rills and Gullies

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

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

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

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.

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.

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

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

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

Deposition During Floods

The Course of a River

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.

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.