R OCKS & W EATHERING Section 2.1

R OCKS & W EATHERING Weathering is the process that breaks down rock & other substances at Earth’s surface. Heat, cold, water, ice, oxygen, carbon dioxide, freezing, & thawing all contribute to weathering. Erosion is the removal of rock particles by wind, water, ice, or gravity. Weathering & erosion work together continuously to wear down & carry away the rocks at Earth’s surface.

T YPES OF W EATHERING The principle of uniformitarianism states that the same processes that operate today operated in the past. The type of weathering in which rocks are physically broken down into smaller pieces is called mechanical weathering (physical process). The causes of mechanical weathering include freezing, thawing, release of pressure, plant growth, actions of animals, and abrasion.

T YPES OF W EATHERING Chemical weathering is the process that breaks down rocks through chemical changes. The causes of chemical weathering include the action of water (dissolving), oxygen (oxidation), carbon dioxide (carbonic acid), living organisms (plant acids), and acid rain.

R ATE OF W EATHERING The most important factors that determine the rate at which weathering occurs are the type of rock & the climate. The minerals that make up the rock determine how fast it weathers. Both chemical & mechanical weathering occur faster in wet climates. Chemical reactions also occur faster at higher temperatures.