Weathering, Erosion, and Soil Formation

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Weathering is the process in which rocks and minerals on Earth's surface are broken down by natural agents. These natural agents include water, ice, acids, salt, plants, animas, and temperature. Weathering can smooth and wear away rock. There is no rock that is hard enough not to be weathered.
There are two types of weathering: mechanical and chemical. Mechanical weathering, also called physical weathering causes rocks to crumble or disintegrate. One example of mechanical weathering is when water gets in cracks of rocks. This water could freeze and expand, widening the cracks and breaking the rock. Another example is when the temperature contracts and expands the rock. This can weaken the rock and cause it to break. Salt also weathers rock. It can get in cracks or pores of rock. Salt crystals can be left behind when saltwater evaporates, leaving behind some salt crystals. These crystals can grow, which puts pressure on the rock and breaks it. A seed can sprout in a rock, making cracks. Animals can break rock by digging and walking on the ground.
Chemical weathering changes the materials in soil or rock. One example is when carbonic acid, which is made when carbon dioxide mixes with water, dissolves rock. This is especially effective when dissolving limestone. Another example is when a rock with iron rusts and expands, which breaks the rock. Chemical weathering can cause holes, sinkholes, and caves to form in rocks.
Weathering is natural, but things humans do can speed it up or slow it down. Air pollution increases the amount of weathering, as does acid rain. Both of these are caused by human actions. Air pollution can be caused by burning things that can release certain chemicals. These chemicals can cause acid rain...

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...re the rain water goes. Time influences the amount of development of the soil. The longer amount of time soil is exposed, the more developed it will become.
There are different layers of soil, called horizons, that are made up of different things. The first layer is the O horizon, which is made of leaf litter and humus (decomposed organic material). The next layer is the A horizon, which is made of humus and mineral particles. The E horizon, which comes after A, is made of sand and silt. The B horizon is made of clay and mineral deposits. The C horizon has broken up bedrock and little organic material. The deepest layer is the R horizon. This horizon is unweathered bedrock.
Soil is very important and takes very long to form. Soil is needed for all crops. We would not have food, wood, or many other things without soil. It is crucial for humans to protect our soil.
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