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| Acid rain. 1 | acidic moisture with a pH below 5.6 . |
| Weathering. | is a mechanical or chemical surface process that breaks rock into smaller pieces.Freezing and thawing,oxigen in the air,plants,an in some cases,it becomes soil. |
| Mechanical weathering.Figure 1. | breaks rocks into smaller pieces without changing them chemically.Two of the many causes are ice wedging and living organisms. |
| Chemical weathering.Table 1 | occurs when the chemical composition of rock changes.This kind of weathering is rapid in tropical regions where it's moist and warm moist of the time.Two important causes of chemical weathering are natural acids and oxigen. |
| Soil. | is a mixture of weathered rock,organic matter,water and air that supports the growth of plant life. |
| Topography. | or surface features,of an area also influence the types of soils that develop.This is because rock fragments move dowhill constantly. |
| Deposition. | dropping of sediments occurs when an agent of erosion can no longer carry its load. |
| Erosion. | is the wearing away and removal of rock or sediment.Erosion occurs because gravity,ice,wind,and water sculpt Earth's surface. |
| Mass movement.Figure 9. a,b,c,d. | can occur anywhere there are hills.or mountains.One place where they often occur is near volcanoes.Are four types of mass movements. |
| Creep. | is common where freezing and thawing occur.As ice expands in soil,it pushes sediments up.Over time,creep can move large amounts of sediment,causing damage to some structures. |
| A slump. | occurs when a mass of rock or sediment moves downhill leaving a curved scar,Slumps are most common in thick layers of loose sediment,but they also form in sedimentary rock. |
| Rock slides. | during a rock slide layers of rock break loose from slopes.Rock slides can be destructive,sometimes destroying entire villages or causing hazards on roads in mountainous areas. |
| Mudflows. | A mudflow is a mass of wet sediment that flows downhill over the ground surface. |
| Deflation. | This erosion of land by wind is called deflation,and can lower the land's surface by several meters. |
| Abrasion. | is a form of erosion that can make pits in rocks and produce smooth,polished surfaces.Abrasion is common in deserts,and cold regions with strong winds. |
| Runoff. | Is an important agent of erosion,especially if the water is moving fast.The more speed water has,the more material it can carry with it. |
| Climate. | affects soil evolution.This is most likely to happen in tropical regions where the climate is warm and moist.It also affects the amount of organic material in soil is humus. |
| Ice. | in some parts of the world,ice is an agent of erosion.In cold regions.Over many years,the snow can accumulate to form large deep masses of ice called glaciers.As glaciers move over Earths surface,they erode materials from some areas and deposit sediment in other areas. |
| Continental Glaciers. | Today continental glaciers in polar regions cover about ten percent of Earth.These glaciers are so large and thick that can bury mountain ranges.Continental glaciers are located near the poles,in Antartica and Greenland. |
| Valley Glaciers. | these glaciers are much smaller and are located in high mountains on many Continents where the average temperature isn't warm enough to melt the ice sheets they move slowly. |
| Rills and Gullies.Figure 17. | Rills are small channels cut into the sediment at Earth's surface.These channels carry more sediment that can be moved sheet flow.As run off continues to flow through the rills more sediment erodes and the channels widens and deepens,they are called gullies. |
| Deltas. Figure 19. | When rivers enter oceans or lakes,the water slows and sediment is deposited.This can form large accumulations of sediment called deltas.The city of New Orleans is built on the delta formed by the Mississippi River. |
| Acid Rain. 2 | is destroying some of world's most famous monuments.Like the Taj Mahal in India,the Acropolis in Greece,and the Colosseum in Italy have stood for centuries. |
