Earth Sciences 1022A/B Lecture Notes - Lecture 5: Parent Material, Humus, Pedogenesis
8 Oct 2016
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Document Summary
After rocks are formed, they are weathered when exposed at the surfaces o. This prepares material for transport by erosional processes in the rock cycle. Two main types of weathering include mechanical (disintegration) and chemical (decomposition) what act together and enhance the effectiveness of each other. Mechanical: reduction of rocks to smaller pieces includes: frost wedging (see diagram) by ice forming in cracks in rocks, breaking them apart o. Sheeting (see diagram) due to expansion on removal of overlying material: biological activity: roots open fractures. Depend on how fractured the rock is, types of minerals and climate. Rock characteristics: granite is made of relatively stable minerals and does not weather easily, marble (soluble) and dark silicate minerals weather easily. Silicate weathering is related to bowen"s reaction series: dark minerals from under high pressure, temperature conditions (unstable under weathering conditions) o. Stable lighter ones form under low pressure and temperature (more stable)
