Cliff-former

A cliff-former is a geological unit of bedrock that resists erosion more strongly than the rock above or below it, so that it stands out as an outcrop with a steep slope angle, a role that is essentially the same as what is elsewhere called a ridge-former and stands in contrast to a slope-former. Which rock type acts as a cliff-former depends on climate: in humid regions sandstone commonly forms cliffs, while in arid regions limestone more often plays that role, and a recent lava flow can also act as a cliff-former. In the Ridge and Valley Appalachians of eastern North America, the Tuscarora, Pocono and Pottsville Formations are the three major ridge-forming rock units, and a Tuscarora Quartzite outcrop in West Virginia is a commonly cited example of a cliff-former in the field.