Erosion
The primary force of erosion is gravity which pulls sediment and water down hill. The end result of erosion is deposition, which is the process in which sediment is laid down in new locations. Most sediment moved by the flowing water is the major agent of erosion which shapes the earth’s surface.
Erosion begins when runoff carries small particles of soil down hill. Runoff gradually form channels in soil which join together and form bigger channels called gullies. Gullies can erode large quantity of soil and flows together to form streams. Most sediment in streams is carried in suspension, in which tiny grains move along with the water. Larger particles of sediment slide, roll, and bounce on the bottom of the stream. This is called saltation. Faster streams carry more sediment, which increases abrasion. A stream’s ability to erode depends mainly on speed. Water in mountains flow faster because water is flowing down on steep slopes. As it goes down the sea the flow gets slower, which makes large sediments settle.
Erosion begins when runoff carries small particles of soil down hill. Runoff gradually form channels in soil which join together and form bigger channels called gullies. Gullies can erode large quantity of soil and flows together to form streams. Most sediment in streams is carried in suspension, in which tiny grains move along with the water. Larger particles of sediment slide, roll, and bounce on the bottom of the stream. This is called saltation. Faster streams carry more sediment, which increases abrasion. A stream’s ability to erode depends mainly on speed. Water in mountains flow faster because water is flowing down on steep slopes. As it goes down the sea the flow gets slower, which makes large sediments settle.
Oxbow lakeWater fallDelta |
V-shaped valleyFlood PlainMeander |
Effects of ErosionWater erosions forms V-shaped valleys, waterfalls, meanders, and oxbow lakes.
As a stream erodes the rock of its streamed, it causes the valley's sides to become steeper. Mass movement on the stream slope causes a V shaped valley. Waterfalls develop on V shaped valleys since streams crosses rock layers that differ in hardness. Harder layers resist erosion on top and softer layers are worn away which makes a cliff. A flood plain is a flat area along a stream that is entirely covered only during times of flood. When a flows across a flood plain, it deposits sediment, making it flat. Over time, sediment builds up into long, low ridges called natural levees. Natural levees helps river to spill over banks except for floods. When a river curves, the outside flows rapidly than the inside which causes sediment to deposit inside and erode on the outside. Over time, this process forms a loop like bend in the river called meander. Sediments build up along the new channel, cutting the old meander which makes a separate, curved lake called an oxbow lake. Effect by DepositionFeatures deposited by flowing water includes alluvial fans and deltas. As a stream flows out into the plains, it slows down and sediment settles out, which results a fan shaped deposit of particles of sediment called alluvial fan. When a stream flows into a lake or an ocean, the sediment is deposited in form of delta. Delta os a mass of sediment deposited where a river enters a large body of water.
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Ground Water Erosion
The process of chemical weathering causes much groundwater erosion, including the formation of caves and sinkholes. Carbon dioxide and rain water combine, forms carbonic acid. The acid rain goes underground and reacts with some rocks causing it to be more acidic. Caves usually form when they are in the saturated zone, below water table. Some of the water drips into the cavern form of rock layers above, carrying dissolved minerals. When the mineral laden water reaches to air, the dissolved carbon dioxide escapes and mineral get left behind. This cavern ceiling of icicle like formation is called stalactite. If the water drips down on the floor, a pillar of minerals called stalagmite forms. When erosion weakens the entire layer of limestone, the ground collapse and makes a sinkhole.