<P> Thermal stress weathering comprises two main types, thermal shock and thermal fatigue . Thermal stress weathering is an important mechanism in deserts, where there is a large diurnal temperature range, hot in the day and cold at night . The repeated heating and cooling exerts stress on the outer layers of rocks, which can cause their outer layers to peel off in thin sheets . The process of peeling off is also called exfoliation . Although temperature changes are the principal driver, moisture can enhance thermal expansion in rock . Forest fires and range fires are also known to cause significant weathering of rocks and boulders exposed along the ground surface . Intense localized heat can rapidly expand a boulder . </P> <P> The thermal heat from wildfire can cause significant weathering of rocks and boulders, heat can rapidly expand a boulder and thermal shock can occur . The differential expansion of a thermal gradient can be understood in terms of stress or of strain, equivalently . At some point, this stress can exceed the strength of the material, causing a crack to form . If nothing stops this crack from propagating through the material, it will result in the object's structure to fail . </P> <Table> <Tr> <Td> </Td> <Td> Parts of this article (those related to conflating frost weathering and frost wedging and also not incorporating hydrofracturing which makes the science here seem wrong See paper = Matsuoka, N.; Murton, J. 2008 . "Frost weathering: recent advances and future directions". Permafrost Periglac . Process . 19: 195--210 . doi: 10.1002 / ppp. 620 referenced on Frost weathering page) need to be updated . Please update this article to reflect recent events or newly available information . (January 2018) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> Parts of this article (those related to conflating frost weathering and frost wedging and also not incorporating hydrofracturing which makes the science here seem wrong See paper = Matsuoka, N.; Murton, J. 2008 . "Frost weathering: recent advances and future directions". Permafrost Periglac . Process . 19: 195--210 . doi: 10.1002 / ppp. 620 referenced on Frost weathering page) need to be updated . Please update this article to reflect recent events or newly available information . (January 2018) </Td> </Tr>

What is hydrolysis and what type of weathering is it