The Role Weathering Plays in Earth Science and Soil

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The term “weathering” is used to describe the effects of exposure to the environmental forces of air, sun, and water. There are two types of weathers: mechanical and chemical. Mechanical weathering involves physical disintegration, while chemical causes decomposition and changes in the elemental properties of the weathered object.

What Does Weathering Do?

Both types of weathering affect everything that comes in contact with atmosphere, from the surfaces of buildings and structures to every living thing, including animals and plants. The long-term effects of the weather on rocks is what creates different types of soil to be formed. Soil, as a result, is a direct product of the weathering process. Soil, also called dirt, is a mixture of rock and mineral particles that support the growth of vegetation.

While it may not seem like rocks are susceptible to change, over the course of many years, they are directly affected by both physical and chemical weathering. They break down, forming minerals inside of the Earth, where the pressure and heat compresses them and changes their physical makeup away from air, sun, and water. When erosion or forces inside the Earth bring those rocks to the surface, exposing them to the elements, the minerals inside the rocks react by expanding and undergoing chemical alterations. Cracks and fissures form in the rocks, allowing the air to seep inside. This process, called oxidation, is what accounts for the rusty red, yellow, and brown colors found within weathered rocks.

Sometimes, plant matter and vegetation can be seen growing out of the cracks of rocks. These plants can root in those cracks under the right conditions, when the cracks allow air, sun and water to seep inside and make ideal conditions for growth.

Resources About Weathering

Information from Georgia Perimeter College about Weathering

Why Weathering is Important to Soil Production and Farming

Chemical weathering changes result when some of the minerals in the rock break down into substances such as clay and iron oxide. As these substances are carried away from the rocks, the rocks begin eroding into smaller and smaller pieces. These small pieces, along with the byproducts created during erosion, help make up new soil.

Soil that is rich in clay is known to be full of nutrients, and is therefore, soil that is exceptional for certain types of farming. The inorganic nutrients in the rock particles that make up the soil vary depending on the composition of the rock that was broken down in the first place. Weather conditions affect the richness of the soil, as the various conditions can deposit more or less valuable minerals in a particular area. The passage of time and the topography of the geographical location, as well as the climate, can have an affect on the fertility of the new soil.

Resources About Soil Producion

University of Wisconsin Information About Soil and Weathering

Weathering and Different Climates

In addition to affecting fertility, weathering also helps soil formation, most rapidly in areas of hot, wet climates, such as the rain forests. These conditions speed the chemicals reactions in the minerals of the rock, and thus, accelerate soil development. But mechanical weathering can also have the same dramatic effects in colder climates. For example, when water caught in the cracks of rocks expands during freezing, it causes pieces of the rock to break off more easily, perpetuating the erosion process. Rock is also worn away by melting snow, as well as the abrasion from particles in the ice, water, or air that run over the rock during the melting process. Salt crystals, plant roots, and burrowing animals also contribute to the mechanical weathering process.

Simulating the effects of weather is possible by placing rocks in a container and then pounding them until the pieces begin to break. This is a simple way to demonstrate and to understand what happens on a large scale throughout the surface of the Earth.

Though soil is a product of weathering, it is not the final stage of the weathering process. Rainfall, condensation and evaporation, among other conditions, cause the soil to shift and erode over time, as does heavy farming. Eventually, the minerals in soil become absorbed by the Earth again, forming rocks, and begin the cycle of development all over again.

Resources About Weathering

About Weathering and Soils at Tulane University

Duke University Slides and Photos of the Weathering Process

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