Editing Weathering (section)

===Thermal stress===
''Thermal stress weathering'' results from the expansion and contraction of rock due to temperature changes. Thermal stress weathering is most effective when the heated portion of the rock is buttressed by surrounding rock, so that it is free to expand in only one direction.<ref name="hall-1999">{{citation|title=The role of thermal stress fatigue in the breakdown of rock in cold regions|journal=Geomorphology|volume=31|issue=1–4|pages=47–63|doi=10.1016/S0169-555X(99)00072-0|year=1999|last1=Hall|first1=Kevin|bibcode=1999Geomo..31...47H}}</ref>

Thermal stress weathering comprises two main types, [[thermal shock]] and [[thermal fatigue]]. Thermal shock takes place when the stresses are so great that the rock cracks immediately, but this is uncommon. More typical is thermal fatigue, in which the stresses are not great enough to cause immediate rock failure, but repeated cycles of stress and release gradually weaken the rocks. Block disintegration, when rock joints weaken from temperature fluctuations and the rock splits into rectangular blocks, can be attributed to thermal fatigue.<ref name="hall-1999"/><ref name=dkp/>

{{Anchor|Insolation weathering}}
Thermal stress weathering is an important mechanism in [[deserts]], where there is a large [[Diurnal temperature variation|diurnal]] temperature range, hot in the day and cold at night.<ref>{{cite book|author=Paradise, T. R.|doi=10.1130/0-8137-2390-6.39|chapter=Petra revisited: An examination of sandstone weathering research in Petra, Jordan|title=Special Paper 390: Stone Decay in the Architectural Environment|date=2005|isbn=0-8137-2390-6|volume=390|pages=39–49}}</ref> As a result, thermal stress weathering is sometimes called '''insolation weathering''', but this is misleading. Thermal stress weathering can be caused by any large change of temperature, and not just intense solar heating. It is likely as important in cold climates as in hot, arid climates.<ref name="hall-1999"/> Wildfires can also be a significant cause of rapid thermal stress weathering.<ref>{{cite journal |last1=Shtober-Zisu |first1=Nurit |last2=Wittenberg |first2=Lea |title=Long-term effects of wildfire on rock weathering and soil stoniness in the Mediterranean landscapes |journal=Science of the Total Environment |date=March 2021 |volume=762 |pages=143125 |doi=10.1016/j.scitotenv.2020.143125 |issn=0048-9697|pmid=33172645 |bibcode=2021ScTEn.76243125S |s2cid=225117000 }}</ref>

The importance of thermal stress weathering has long been discounted by geologists,{{sfn|Blatt|Middleton|Murray|1980|p=247}}{{sfn|Leeder|2011|p=18}} based on experiments in the early 20th century that seemed to show that its effects were unimportant. These experiments have since been criticized as unrealistic, since the rock samples were small, were polished (which reduces nucleation of fractures), and were not buttressed. These small samples were thus able to expand freely in all directions when heated in experimental ovens, which failed to produce the kinds of stress likely in natural settings. The experiments were also more sensitive to thermal shock than thermal fatigue, but thermal fatigue is likely the more important mechanism in nature. [[Geomorphology|Geomorphologists]] have begun to reemphasize the importance of thermal stress weathering, particularly in cold climates.<ref name="hall-1999"/>