Onion skin weathering is a Geological process that happens mainly in deserts. As the rock heats up and expands by day, and cools and contracts by night, stress is often exerted on the outer layers. The stress causes the peeling off of the outer layers of rocks in thin sheets. Though this is caused mainly by temperature changes, thermal expansion is enhanced by the presence of moisture.
Onion skin weathering has to do with rocks mostly in the desert. It is when the hot temperature of the day is then reduced to a cold temperature at night. This change in temperature causes layers of the rock to peel off like onion skin coming off. Therefore it is called onion skin weathering.
