Weathering, Erosion and Building Soil World Geo, pgs Shaping the Earth: External Forces

Weathering External force that refers to the physical and chemical processes that change the characteristics of rock on or near the Earth’s surface Occurs slowly (over years) Breaks down rock into smaller pieces called sediment- very fine particles of rock ( mud, sand and silt) 2 types: Mechanical vs Chemical weathering

Mechanical Weathering Processes that help break rock into smaller sediment pieces Does not change the composition (the make-up of) the rock, but changes the size. Effects such as frost or plant roots can break apart rocks, even human activity such as construction, drilling/blasting and mining. Example: Crystals growing in cracks/crevices can break apart rocks

Chemical Weathering Occurs when the composition changes into a new substance Interaction between elements in the air or water and the minerals in the rock Decomposition- to break down or break up; to break apart Location and climate also plays apart in how a rock decomposes. Example: Warm/moist climates will produce more chemical weathering than cool dry.

Erosion Occurs when weathered material is moved by wind, water, ice or gravity. For erosion to occur, a transporting agent like water, needs to be present. Erosion helps to forms or reshapes landforms and coastal regions, waterbeds and riverbanks. There is also water, glacial and wind erosion (pages 43-44)

Building Soil Weathering and erosion are part of a process that produces soil Soil- the loose mixture of organic matter, air, rock and water. The variety of soils and the climates in which they are found are determined by the types of vegetation.