Earth Science Weathering PDF

EARTH SCIENCE WEATHERING  At the end of the lesson, students should be able to: Define how rocks undergo weathering. Identify the different types of weathering.  GIVE YOUR THOUGHTS ABOUT “WEATHERING” WEATHERING Weathering is the process of breakdown of rocks a...

EARTH SCIENCE WEATHERING  At the end of the lesson, students should be able to: Define how rocks undergo weathering. Identify the different types of weathering.  GIVE YOUR THOUGHTS ABOUT “WEATHERING” WEATHERING Weathering is 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.  TYPES OF WEATHERING Physical (Mechanical) Chemical Biological  PHYSICAL WEATHERING Caused by the effects of changing temperatures on rocks, causing the rock to break apart. It occurs either through repeated melting and freezing of water or through expansion and contraction of the surface layer of rocks.  CAUSES OF PHYSICAL WEATHERING  Abrasion It occurs when rocks surface is frequently exposed to water, wind and gravity.  Freeze-thaw It occurs when water continually seeps into cracks, freezes and expands, eventually breaking the rock apart. It occurs in mountainous regions like the Alps or Snowdonia.  Exfoliation It can happen as cracks develop parallel to the land surface as a consequence of the reduction in pressure during uplift and erosion.  CHEMICAL WEATHERING Caused by rainwater reacting with the mineral grains in rocks to form new minerals (clays) and soluble salts. Chemical weathering (especially hydrolysis and oxidation) is the first stage in the production of  TYPES OF CHEMICAL WEATHERING  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.  Acidification Polluting gases, like sulphur dioxide and nitrogen oxide dissolve in rainwater to make stronger acids. When this rainwater falls, we get acid rain.  Hydrolysis It is a common form of a chemical reaction where water is mostly used to break down the chemical bonds that exists between a particular substance. Eventually, rocks will have a clay-like structure  Hydration A type of chemical weathering where water reacts chemically with the rocks, modifying its chemical structure.  Oxidation The breakdown of rock by oxygen and water, often giving iron rich rocks a rusty-colored weathered surface.  BIOLOGICAL WEATHERING Occurs when rocks are weakened by different biological agents like plants and animals. When plant roots grow through rocks, it creates fracture and cracks that result eventually to rock breakage.  CAUSES OF BIOLOGICAL WEATHERING  BIOLOGICAL WEATHERING Biological Weathering by Physical Means. Burrowing animals like shrews, moles and earthworms create holes on the ground by excavation and move the rock fragments to the surface.  BIOLOGICAL WEATHERING Biological Weathering by Chemical Compounds. Some plants and animals also produced acidic substances that react with the rock and cause its slow disintegration.  Performance Task 1 Create a group with 5 members. Bring the following materials: Chalk (at least 2) 2 plastic cups Vinegar (pack) Salt (small pack)