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Heat‑driven expansion and contraction in deserts cause rock layers to peel away in a process known as exfoliation. During the day, temperatures can exceed 40 °C (104 °F), forcing rocks to expand. At night, the cooling to around 5 °C (41 °F) or lower causes the outer layers to contract, weakening the structure. Repeated cycles of expansion and contraction fracture the rock, allowing slabs to fall off.
When temperatures fluctuate around the 0 °C (32 °F) mark, water infiltrates rock fractures. Upon freezing, water expands by roughly 9 %, exerting pressure that widens the crack. A cycle of freezing and thawing—documented by the HyperPhysics site at Georgia State University—gradually breaks the rock apart.
Chemical reactions on the rock’s surface dissolve minerals. In warm, humid regions, rainfall contains dissolved carbon dioxide forming weak carbonic acid. This acid reacts with calcium carbonate in rocks such as chalk and limestone, a process called carbonation, making the rock soluble and gradually eroding it. Iron‑rich minerals oxidize (rust), altering the rock’s structure and promoting disintegration.
Plants and animals combine mechanical and chemical forces. Growing roots pry into fractures, physically expanding cracks. When roots decay, they release organic acids that chemically weather the surrounding rock. Human foot traffic and other animal movement also erode rock surfaces through repeated friction. Over time, these processes generate soil and create new habitats for subsequent vegetation.
