WEATHERING

WEATHERINGWhen rocks (igneous, sedimentary, or metamorphic) are at or near the surface of the earth they are exposed to the processes of weathering.A process that breaks the rocks into smaller pieces or sediments Happened by external force (wind, rain, temperature.)

3 type of weathering: Physical weatheringChemical weatheringBiological weathering

PHYSICAL WEATHERINGBy temperature changes: Heat energy heat up rocks to very high temperatures causes rocks to expand. As temperatures fall, the rocks cool down and contract. Continuous expansion and contraction causes pressure on the outer layers of the rock. It lead cracking to the rock.By water, wind and wave:Winds, water and waves pound on rocks and wears them up. Prolonged action causes larger rocks with rugged surfaces to smoothen. During runoff, water carries sand and smaller debris and smashes them against larger rocks in their path. Caused wearing of rock.Freeze and thawing:When water collects in rock pores and cracks and spaces they expand when they freeze, particularly in cold climates. The freezing widens and causes additional cracks. When the ice thaws, the water enters into new cracks again and causes further cracks as they freeze. Soon the rocks break apart.

CHEMICAL WEATHERINGInvolves the reaction of some chemicals on rocks. Some rocks (limestone and chalk) are more prone to chemical weathering than others such as granite. Because limestone contains minerals such as calcium carbonate, which readily reacts with rainwater. This chemical reaction produces new soluble substances that are easily washed away.Rain water contains an acid (carbonic acid). When acidic rainwater falls and stays on rocks, some minerals in the rocks may react chemically with it and cause weathering.Key fact in the creation of caves and caverns.Hydrolysis - water (H2O) separates into H+ and OH- ions, the elements react with ions in the minerals and destroy their atomic compositions, and form new minerals.Example:Knife exposure to water and oxygen, caused knife becomes a rusty piece of junk. The minerals in the knife have chemically weathered, changing from iron (Fe) to iron oxides (Fe2O3, hematite or FeOOH, goethite) better known as rust. (Oxidation)

BIOLOGICAL WEATHERINGCommom and we see it around - caused by living organismsExample: Trees put down roots through joints or cracks in the rock in order to find moisture. As the tree grows, the roots gradually prize the rock apart.Animal that can burrow into a crack in a rock. There are many insects and bigger animals that live in holes in the ground or rocks. They burrow and widen cracks and end up breaking rocks apart.Walking and construction activities like road building, mining and the like involve people ripping rocks apart.