Weathering and Erosion

Weathering

• Weathering causes the disintegration of rock near the surface of the earth. Plant and animal life, atmosphere and water are the major causes of weathering. Weathering breaks down and loosens the surface minerals of rock so they can be transported away by agents of erosion such as water, wind and ice. There are two types of weathering: mechanical and chemical.

Types of weathering

Mechanical Weathering

Mechanical weathering is the disintegration of rock into smaller and smaller fragments. Frost action is an effective form of mechanical weathering. When water trickles down into fractures and pores of rock, then freezes, its volume increases by almost 10 percent. This causes outward pressure of about 30,000 pounds per square inch at -7.6 Fahrenheit. Frost action causes rocks to be broken apart into angular fragments. Idaho's extreme temperature range in the high country causes frost action to be a very important form of weathering.

Chemical Weathering

Chemical weathering transforms the original material into a substance with a different composition and different physical characteristics. The new substance is typically much softer and more susceptible to agents of erosion than the original material. The rate of chemical weathering is greatly accelerated by the presence of warm temperatures and moisture. Also, some minerals are more vulnerable to chemical weathering than others. For example, feldspar is far more reactive than quartz.FIGURE : Chemical weathering of a statue, caused by acid rain

Erosion

Once the small pieces of rocks are changed or broken apart by weathering, they may start to be moved by wind, water, or ice. When the

smaller rock pieces (now pebbles, sand or soil)are moved by these natural forces, it is called erosion.

Types of Erosion

Wind Erosion

• Wind erosion, though it may be small where you live, can take quite a toll on areas of the world covered in desert. Wind erosion is simple... light objects, such as rocks and pebbles are carried by the wind and can hit landforms, eroding materials off them, that are carried off in the wind.

Glacier Erosion

• Ice erosion, besides that of hail, comes mostly in the form of glacier erosion. Glaciers are giant bodies of ice that can pick up huge pieces of rock, some even as big as houses. A combination of the water, ice, and picked up sediment, create a powerful eroding machine.

Soil Erosion

• Soil erosion pays the biggest

price to farmers. Flooding, wind etc.

can carry the topsoil away from

farmlands, and make

the soil unfertile.

Erosion caused by rain or irrigation, showing how

water can wash away the soil

Soil erosion caused by rain

Erosion by waves, forming a natural bridge

Chemical weatheringcausing minerals in

therocks to dissolve, andthen form stalactitesand stalagmites in a

cave.

Mechanical weathering called exfoliation causing the rocks to break

into layers

REFERENCE

• http://www.doe.virginia.gov/instruction/gifted_ed/project_promise/science_curriculum/grade_two/handouts/earth_science/weathering_erosion_pictures.pdf

• http://imnh.isu.edu/digitalatlas/geo/basics/weathrng.htm

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

Made byUROOJ AYAZ

VIII – BBEACONHOUSE SCHOOL

All the information is used for educational purpose only…..