A large block of rock fell from this spot! |
Large blocks of limestone fall from these cliffs occasionally, but large blocks of shale rarely do. Why?
Rocks weather (or weaken) and erode (or break away) differently. Limestone is a type of rock made of large and small pieces of shells and skeletons of sea life. These grains are glued together by minerals (natural earth materials which form crystals). These glues may make up more than half of the rock's volume, so limestones weather slowly and break into large chunks. Shale is a type of rock made mostly of tiny grains and few other minerals. After many years, the wind, rain, and ice break shale quickly into small chips.