GLGY 353 Study Guide - Midterm Guide: Winnowing, Cross-Bedding, Clastic Rock
23 Mar 2016
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Bedrock gets increasingly broken up as it gets closer to the earth"s surface which enhances chemical weathering along fractures. In addiion, rocks weather at the surface of the earth because it is trying to change into a more stable state, because the pressure/temperature condiions that it formed under was likely diferent than the earth"s surface. The exposure to weathering agents (air, water) also enhances weathering. Relaive resistances to chemical weathering of diferent silicate minerals: Quartz, muscovite, bioite, orthoclase, amphibole, pyroxene, olivine (most resistant-least resistant). Quartz is a tectosilicate (four covalent bonds; all silicate tetrahedral connected to one another). Olivine is a nesosilicate (tetrahedral are only connected by intersiial caions weaker bonds). In addiion, many silicates, such as alkali-feldspar and olivine, are highly suscepible to chemical weathering via hydrolysis, whereas quartz is not. Role of fractures, water, plants/fungi in regolith creaion: Root pry: plant roots mechanically weather the rock. Roots follow nooks and crannies and expand them.
