Water Erosion
- RUNOFF AND EROSION:3Moving water is the major agent of the erosion that has shaped Earths land surface.
- Erosion by water begins with the splash of rain, Some rainfall sinks into the ground. Some of the water evaporates or is taken up by plants. The force of a falling raindrop can loosen and pick up soil particles. As water moves over the land, it carries these particles with it. This moving water is called runoff.
- Runoff is water that moves over Earths surface. When runoff flows in a thin layer over the land, it may cause a type of erosion called sheet erosion.
- AMOUNT OF RUNOFF:The amount of runoff in an area depends on five main factors. Factor one is the amount of rain the area receives, factor two is the amount of vegetation, factor three is the type of soil the area has, factor four is the shape of the land, finally the fifth factor is how the people use the land.
- More runoff means more erosion. Runoff also increases when farmers cut down their crops.
- RILLS AND GULLIES:As runoff travels, it forms tiny grooves in the soil called rills. As many rills flow into one another, they grow larger, forming gullies.
- A gully is a large groove, or channel, in the soil that carries runoff after s rainstorm. As water flows through gillies through erosion. Gullies contain water only after it rains.
- STREAMS AND RIVERS:A stream is a channel along which water is continually flowing down a slope. Unlike gullies streams rarely dry up. Small streams are often called creeks or brooks. As streams flow together, they form larger and larger bodies of flowing water.
- TRIBUTARIES:A tributary is a stream or river that flows into a larger river.
- EROSION BY RIVERS:Through erosion a river creates valleys, waterfalls, floodplains, meanders, and oxbow lakes.
- MEANDERS:A meander is a loop like bend in the course of a river. As the river winds from side to side, it tends to erode the outer bank and deposit sediment on the inner bank of the bend.
- OXBOW LAKES:An Oxbow lake is a meander that has been cut off from the river. It may form when a river floods. As the flood water fall, sediments dam up the ends up a meander. The meander has become an oxbow lake.
- ALLUVIAL FANS:Deposition creates landforms such as alluvial fans is a wide, sloping deposit of sediment formed where a stream leaves a mountain range.
- DELTAS:Sediment deposited where a river flows into an ocean or lake builds up a landform called a delta
- Deltas can be a variety of shapes. Some are arc shaped, others are triangle shaped.
- SOIL ON FLOOD PLAINS:Deposition can also occur during floods. Then heavy rains or melting of snow cause a river to rise above its banks and spread out over its floodplain. When the flood water finally retreats, it deposits sediment as new soil.
- GROUNDWATER EROSION:Groundwater is the term geologists use for this underground water. Like running water on the surface, groundwater affects the shape of the land.Groundwater can cause erosion through a process of chemical weathering.
- CAVE FORMATIONS:A deposit that hangs like an icicle from the root of a cave is known as a stalactite.
- Slow dripping builds up a cone shaped stalagmite from the cave floor.
- KARST TOPOGRAPHY:This type of landscape is called Karst topography after a region in Eastern Europe.