waxing slope

The component parts of a hillside are (1) the convex waxing slope at the top, eroding from top down; (2) the extensive downward free face, or constant slope; and (3) gentler concave waning slopes at the foot, where fine materials collect after being brought down from erosion on higher slopes. Waning slopes can come to dominate landscapes as erosion erases differences in elevation, and are sometimes used as a metaphor for failing or diminished human expectations.

William Kittredge