Onion Skin weathering is also known as exfoliation weathering. Onion skin weathering often occurs in hot areas, like deserts where the temperature is often high in the day time and eventually the temperature decreases in the night. During daytime, the rocks are exposed to the sun which causes the rocks to expand. However during the night, the rock contracts because of the cooler temperature. This process is continued and over time, the surface of the rock begins to flake off.
(Picture to the Left) Here you can see the rock has an almost fish scale like texture. This is caused when the rock is exposed to temperature that rapidly changes each time of the day.
(Picture to the Right) The picture here shows a diagram of how onion skin/ exfoliation weathering takes place.