16: Weathering and Soils
- Page ID
- 55128
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- 16.1: Mechanical Weathering
- This section examines mechanical weathering, the physical breakdown of rock into smaller pieces without changing its chemical composition. Processes such as frost wedging, abrasion, pressure release, and biological activity gradually break exposed rock apart and increase the surface area available for further weathering.
- 16.2: Chemical Weathering
- This section explores chemical weathering, in which minerals in rocks are altered or dissolved through reactions with water, oxygen, acids, and other substances. It examines several important chemical weathering processes and considers how environmental conditions influence the rate at which rocks and minerals break down.
- 16.3: The Products of Weathering and Erosion
- This section examines what happens to Earth materials as weathering breaks them down and erosion transports them. Weathering produces particles and dissolved materials that can be moved by water, wind, ice, and gravity, connecting the breakdown of rock at Earth’s surface with sediment transport and deposition.
- 16.4: Weathering and the Formation of Soil
- This section explores how weathered rock, organic material, water, and air combine over time to produce soil. It examines the development of soil horizons and the factors that influence soil formation, showing how geology, climate, organisms, topography, and time contribute to the soils found at Earth’s surface.
Chapter 16: Weathering and Soils - Introduction
Earth’s surface is constantly being changed. While the previous chapter examined processes driven largely by energy from within Earth, such as plate tectonics, earthquakes, and volcanism, this chapter turns to processes operating at and near the surface. Once rocks are exposed to the atmosphere, water, and living organisms, they begin to break down and change.
Weathering is the breakdown or alteration of rock at or near Earth’s surface. Mechanical weathering physically breaks rock into smaller pieces without changing the minerals themselves, while chemical weathering changes minerals through chemical reactions. These processes often work together: breaking a rock into smaller pieces exposes additional surface area where chemical reactions can occur.
The products of weathering do not necessarily remain where they form. Erosion removes and transports weathered material through processes involving water, wind, ice, and gravity. Over time, weathering and erosion help reshape landscapes while also supplying the sediment that becomes incorporated into other parts of the geological system.
Weathering also plays an essential role in the development of soil. Soil is more than broken rock; it develops through interactions among mineral material, organic matter, water, air, and living organisms. Its characteristics reflect the rock from which it develops as well as climate, topography, biological activity, and the amount of time available for soil formation. By examining weathering and soils, we can see another way in which the atmosphere, hydrosphere, biosphere, and geosphere continually interact at Earth’s surface.