Erosion EarthCache

Erosion

What is erosion? 
Erosion is the wearing away of the land by forces such as water, wind, and ice. Erosion has helped to form many interesting features of the Earth's surface including mountain peaks, valleys, and coastlines. 

What causes erosion?
Erosion of land happens in a variety of different ways. It could be caused by water, wind, glacier, sea or people. But for the most part erosion is caused by water, wind, ice and people..

4 Types of erosion:

Erosion by Water

• Water is the main cause of erosion on Earth. Although water may not seem powerful at first, it is one of the most powerful forces on the planet. Here are some of the ways that water causes erosion.
• Rainfall can cause erosion both when the rain hits the surface of the Earth, called splash erosion, and when raindrops accumulate and flow like small streams
• Acid rain has many ecological effects, which includes causing damage to rocks, buildings and monuments. But none is greater than its impact on lakes, streams, wetlands, and other aquatic environments.

• Rushing streams and rivers wear away their banks, creating larger and larger valleys. The third largest canyon created by a River is The Blyde River Canyon. In a span over many years, Blyde River and the Treur River cut deeper and deeper into the land, It eventually formed The Blyde River Canyon, which is  25 kilometres in length and is, on average, around 750 metres deep.
• Erosion by water changes the shape of coastlines. Waves constantly crash against shores. They pound rocks into pebbles and reduce pebbles to sand. Water sometimes takes sand
• away from beaches. As was the case in March 2007 when a storm event along the KwaZulu-Natal (KZN) coastline resulted in approximately 4 000 000 m³ of sand being eroded from the coastline, which is equitable to nine years’ worth of sediment.

• Water erosion occurs from the chemicals in the water, and the force of the flow of water in the river. There are many chemicals in the water of a river, and those chemicals can break down certain rocks, such as limestone or chalk. A prime example of this is Bourke's Luck Potholes in the Blyde River Canyon.

Erosion by Wind

• Wind is also an agent of erosion. It carries dust, sand, and volcanic ash from one place to another. Wind can sometimes blow sand into towering dunes.

• In dry areas, windblown sand blasts against rock with tremendous force, slowly wearing away the soft rock.

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Erosion by Ice

• Ice erosion, besides that of hail, comes mostly in the form of glacier erosion
• Glaciers are giant rivers of ice that slowly move carving out valleys and shaping mountains.
• Glaciers move slowly downhill and across the land. As they move, they pick up everything in their path, from tiny grains of sand to huge boulders. The rocks carried by a glacier rub against the ground below, eroding both the ground and the rock. 
• The classic U-shaped valley is a typical expression of glacial erosion, but situations can occur where the glacier effects little to no change in the landscape.
• There has been much discussion regarding possible glaciation in southern Africa but recent work by Mills (2006) has provided the first scientific evidence pointing to a possible limited glaciation in parts of the Lesotho-Drakensberg area, however this evidence does not support glacier erosion.

• Today, in places such as Greenland and Antarctica, glaciers continue to erode the earth. These ice sheets, sometimes more than a mile thick, carry rocks and other debris downhill toward the sea. Eroded sediment is often visible on and around glaciers. This material is called moraine.

Erosion and People

• Erosion is a natural process, but human activity can make it happen more quickly. This happens through farming, ranching, cutting down forests, and the building of roads and cities.
• Trees and plants hold soil in place. When people cut down forests or plow up grasses for agriculture or development, the soil washes away or blows away more easily. Landslides become more common. Water also rushes over exposed soil rather than soaking into it, causing flooding.
• Soil erosion pays the biggest price to farmers. Flooding, wind etc. can carry the topsoil away from farmlands, and make the soil unfertile. Human activity has caused about one million acres of topsoil to erode each year. 

Reference:

http://www.ducksters.com/science/earth_science/erosion.php

http://environment.nationalgeographic.com/environment/global-warming/acid-rain-overview/

https://www.capetown.gov.za/en/DRM/Pages/CoastalErosion.aspx

http://repository.up.ac.za/xmlui/bitstream/handle/2263/15429/Hall_Shape%282010%29.pdf?sequence=1&isAllowed=y

http://pubs.usgs.gov/pp/p1386g/africa.pdf

http://www.odec.ca/projects/2004/derk4d0/public_html/differenttypesoferosion.htm

http://education.nationalgeographic.com/encyclopedia/erosion/

http://www.grainsa.co.za/soil-erosion-in-south-africa---its-nature-and-distribution

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