Onion skin weathering is a geological process that occurs when a rock's outer layer peels off due to extreme variations in temperatures. This type of rock weathering typically occurs in desert areas where rocks are subjected to extreme heat during the day, which causes rocks to expand. When temperatures drop during the night, the rocks contract.
The outer layers of rocks will begin to flake off over a period of time due to these temperature extremes. Another name for this type of weathering is exfoliation weathering. This is one type of erosion that rocks can undergo.
Some other types of rock erosion are biological, chemical or freeze-thaw weathering. The weathering process dissolves or breaks down rocks into smaller pieces.