Weathering, Soils, & Erosion

#1 Weathering is the break up of rock due to exposure to processes that occur at the Earth’s surface. Weathering is the break up of rock due to exposure to processes that occur at the Earth’s surface. There are 2 types of weathering There are 2 types of weathering Mechanical weather (disintegration) takes place when a rock is split or broken into smaller pieces of the same rock without changing it’s composition. Mechanical weather (disintegration) takes place when a rock is split or broken into smaller pieces of the same rock without changing it’s composition. Mechanical weathering is also called physical weathering Mechanical weathering is also called physical weathering Chemical weathering (decompostion) occurs when the rock’s minerals are changed into different minerals. Chemical weathering (decompostion) occurs when the rock’s minerals are changed into different minerals. The 2 types of weathering usually occur together. The 2 types of weathering usually occur together.

#2 Water occupies about 10% more space when if freezes Water occupies about 10% more space when if freezes When water falls into cracks in rocks and then freezes it will force the rock apart. When water falls into cracks in rocks and then freezes it will force the rock apart. This is called frost wedging. This is called frost wedging. Frost wedging occurs when the temperature fluctuates above and below the freezing point. Frost wedging occurs when the temperature fluctuates above and below the freezing point. Frost wedging also causes potholes to form on the streets Frost wedging also causes potholes to form on the streets

#3 Wind, water, and ice can move rocks. Wind, water, and ice can move rocks. As rocks are tumbled along, they scape and grind against one another. As rocks are tumbled along, they scape and grind against one another. This process is known as abrasion. This process is known as abrasion. Sand and soil are products of abrasion. Sand and soil are products of abrasion.

#4 Plants and animals can contribute to the weathering of rocks. Plants and animals can contribute to the weathering of rocks. Lichens, mosses, small plants/trees can grow on rocks. Lichens, mosses, small plants/trees can grow on rocks. They can wedge their roots into cracks and crevices and force them open. They can wedge their roots into cracks and crevices and force them open. Ants, moles, rabbits, and other rodents dig holes into the soil which can allow water to reach the bedrock and weather it. Ants, moles, rabbits, and other rodents dig holes into the soil which can allow water to reach the bedrock and weather it.

#5 The upward expansion of rocks that are formed deep underground may result in exfoliation, which is the removal of rock in layers. The upward expansion of rocks that are formed deep underground may result in exfoliation, which is the removal of rock in layers.

#6 Chemical weathering occurs almost everywhere because water is found almost everywhere. Chemical weathering occurs almost everywhere because water is found almost everywhere. All chemical weathering involved water. All chemical weathering involved water. Other agents of weathering include oxygen (oxidation) and acid rain/snow Other agents of weathering include oxygen (oxidation) and acid rain/snow

#7 The chemical weathering by reaction of water with other substances is called hydrolysis. The chemical weathering by reaction of water with other substances is called hydrolysis. Common materials that undergo hydrolysis are feldspar, horneblende, and augite. Common materials that undergo hydrolysis are feldspar, horneblende, and augite.

#8 Water’s chemical effect on minerals is increased by the presence of acids that are dissolved in the water. Water’s chemical effect on minerals is increased by the presence of acids that are dissolved in the water. A common acid found in water is carbonic acid, which forms when carbon dioxide in the atmosphere dissolves in falling precipitation. A common acid found in water is carbonic acid, which forms when carbon dioxide in the atmosphere dissolves in falling precipitation. Carbonic acid has great effect on calcite. Carbonic acid has great effect on calcite. Carbonic acid will completely dissolve calcite. Carbonic acid will completely dissolve calcite. This can cause the formation of great underground caves/caverns in limestone bedrock. This can cause the formation of great underground caves/caverns in limestone bedrock.

#9 The brown or red color in some exposed rocks may be the result of a process called oxidation. The brown or red color in some exposed rocks may be the result of a process called oxidation. Oxidation is the chemical reaction of oxygen with other substances. Oxidation is the chemical reaction of oxygen with other substances. Oxidation is very effective at weathering substances that have iron in them. Oxidation is very effective at weathering substances that have iron in them.

#10 Weathering is usually a very slow process. Weathering is usually a very slow process. The rate at which a rock weathers is affected by the amount of the rock’s surface that is exposed to the chemical weathering process. The rate at which a rock weathers is affected by the amount of the rock’s surface that is exposed to the chemical weathering process.

More #10 Breaking a rock into smaller pieces accelerates the weathering process. Breaking a rock into smaller pieces accelerates the weathering process. The composition of a rock affects the weathering rate also. The composition of a rock affects the weathering rate also. Often, sedimentary rocks weather more rapidly than igneous or metamorphic rocks do. Often, sedimentary rocks weather more rapidly than igneous or metamorphic rocks do.

#11 Climate is another factor that affects the weathering process. Climate is another factor that affects the weathering process. In general, warm and wet climates are conducive to both types of weathering. In general, warm and wet climates are conducive to both types of weathering. In a warm climate, water is not solid and many chemical processes actually speed up when conditions are warm. In a warm climate, water is not solid and many chemical processes actually speed up when conditions are warm.

#12 Mass movement refers to the downward tranportation of materials by gravity. Mass movement refers to the downward tranportation of materials by gravity. Erosion is the removal and transport of materials by natural agents such as wind and running water Erosion is the removal and transport of materials by natural agents such as wind and running water

#13 Geologists use the term talus to refer to rock fragments that have been weathered from a cliff and pulled down by gravity. Geologists use the term talus to refer to rock fragments that have been weathered from a cliff and pulled down by gravity. Landslide is the term for the movement of a mass of rock or loose soil down the side of a hill, cliff, or mountain. Landslide is the term for the movement of a mass of rock or loose soil down the side of a hill, cliff, or mountain.

14 Creep is a slow, imperceptible movement of soil down a slope. Creep is a slow, imperceptible movement of soil down a slope. Slump occurs when blocks of land tilt and move downhill. Slump occurs when blocks of land tilt and move downhill. During earthflow, a mass of weathered material that has been saturated with water flows downhill. During earthflow, a mass of weathered material that has been saturated with water flows downhill. A mudflow is the rapid movement of water that contains large amount of suspended silt and clay. A mudflow is the rapid movement of water that contains large amount of suspended silt and clay.

#15 The material from which soil forms is called parent material. The material from which soil forms is called parent material. A soil whose parent material is the bedrock beneath the soil is called residual soil. A soil whose parent material is the bedrock beneath the soil is called residual soil. Soils formed from transported materials are called transported soils. Soils formed from transported materials are called transported soils.

More #15 A cross section of the earth exposed by digging is called the soil profile. A cross section of the earth exposed by digging is called the soil profile. In mature soil, there are 3 distinct zones called soil horizons. In mature soil, there are 3 distinct zones called soil horizons. The A horizon is the topsoil The A horizon is the topsoil The B horizon starts with the subsoil The B horizon starts with the subsoil The C horizon is made of slightly weathered plant material. The C horizon is made of slightly weathered plant material.

#16 Soil fertility is the ability of soil to grow plants. Soil fertility is the ability of soil to grow plants. Soil depletion occurs when the soil gradually becomes so lacking in nutrients that it can no longer grow crops. Soil depletion occurs when the soil gradually becomes so lacking in nutrients that it can no longer grow crops. Soil depletion can be minimized by farmers doing things such as rotating crops and adding artificial fertilizers. Soil depletion can be minimized by farmers doing things such as rotating crops and adding artificial fertilizers. Runoff from fertilized fields can and do pollute rivers and lakes. Runoff from fertilized fields can and do pollute rivers and lakes.

#17 Irrigation of desert soils can cause mineral buildup in the soils and result in salinization, which means the soil becomes salty. Irrigation of desert soils can cause mineral buildup in the soils and result in salinization, which means the soil becomes salty.