Weathering PDF

WEATHERING The earth’s surface is composed of water and landmasses. The solid portion is made out of rocks and minerals that could experience changes either physically or chemically.  Weathering the process of breakdown of rocks at the Earth’s surface, by the action of water, ice, acids...

WEATHERING The earth’s surface is composed of water and landmasses. The solid portion is made out of rocks and minerals that could experience changes either physically or chemically.  Weathering the process of breakdown of rocks at the Earth’s surface, by the action of water, ice, acids, salts, plants, animals, gravity and changing temperatures  3 Types of Weathering Physical Chemical Biological  A. Physical Weathering caused by the effects of changing temperatures on rocks, causing the rock to break apart  1. Abrasion It occurs when rocks surface is frequently exposed to water, wind and gravity.  2. Freeze-thaw It occurs when water continually seeps into cracks, freezes and expands, eventually breaking the rock apart.  3. Exfoliation It can happen as cracks develop parallel to the land surface as a consequence of the reduction in pressure during uplift and erosion.  B. Chemical Weathering caused by rainwater reacting with the mineral grains in rocks to form new minerals (clays) and soluble salts.  TYPES OF CHEMICAL WEATHERING  1. Carbonation Carbon dioxide in the air dissolves in rainwater and becomes weakly acidic. This weak “carbonic acid” can dissolve limestone as it seeps into cracks and cavities. Over many years, solution of the rock can form spectacular cave systems.  2. Acidification Polluting gases, like sulfur dioxide and nitrogen oxide dissolve in rainwater to make stronger acids. When this rainwater falls, we get acid rain. This acid attacks many rock types, both by solution and hydrolysis, seriously damaging buildings and monuments. 3. Hydrolysis The breakdown of rock by acidic water to produce clay and soluble salts. Hydrolysis takes place when acid rain reacts with rock-forming minerals such as feldspar to produce clay and salts that are removed in solution. 3. Hydrolysis  4. Hydration A type of chemical weathering where water reacts chemically with the rocks, modifying its chemical structure. Example: H2O (water) is added to CaSO4 (calcium sulfate) to create CaSO4 + 2H2O (calcium sulfate dihydrate). It changes from anhydrite to gypsum.  5. Oxidation The breakdown of rock by oxygen and water, often giving iron-rich rocks a rusty- colored weathered surface  C. Biological Weathering 1. Biological Weathering by Physical Means  C. Biological Weathering 2. Biological Weathering by Chemical Compounds Some plants and animals also produced acidic substances that react with the rock and cause its slow disintegration.  ACTIVITY Write a tagline about weathering. (It could also be a hugot line or a Pick up line