Answer
The process that caused the separation of relatively thin slabs of granite from a rock mass is known as exfoliation or unloading. Exfoliation occurs due to the release of confining pressure on the rock surface, often as a result of erosion or the removal of overlying rock layers.
During the formation of the rock mass, deep within the Earth's crust, the granite was subjected to high pressure and temperature, which caused it to be compacted and tightly bound. Over time, as erosion and weathering processes occur, the overlying layers of rocks are gradually stripped away, reducing the confining pressure on the granite beneath.
As the confining pressure decreases, the granite expands and fractures parallel to the surface, resulting in the formation of thin slabs or sheets. These slabs detach from the rock mass, exposing fresh surfaces. This process is similar to the peeling of layers from an onion, where each layer represents a separate exfoliation event.
Exfoliation is particularly common in areas with a significant daily temperature variation, as thermal expansion and contraction further contribute to the stress on the rock and promote the separation of slabs. The exfoliated slabs may eventually break down into smaller pieces through subsequent weathering processes, further contributing to the process of mechanical weathering and the gradual breakdown of the rock mass.
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