Rock exfoliation is the separation of successive thin shells from massive rock such as granite or basalt. It is thought to be caused by a release of pressure due to unloading, where above rock is eroded away and the expansion of the exposed rock due to reduced pressure results in fracturing.
While often this can be a slow process, a recently released video shows that it can happen rapidly and relatively explosively. In the area of Twain Harte Lake in the Sierra Nevada, starting on August 3rd, outcrops of granite have been furiously exfoliating. Lucky for us, one example has been caught on camera.