Monuments are like inselbergs in that most are isolated outliers of plateaus.

Unlike inselbergs, whose shapes are conical or pyramidal, monuments tend to have vertical sides.

Outstanding examples of tall, massive, steep-sided monuments, resulting from erosion of thick, nearly horizontal beds of sandstone, can be seen in Monument Valley, Arizona.

If the beds are tilted or folded, or otherwise internally inhomogeneous, the isolated erosional remnants show these characteristics by their less regular shapes, and they do not resemble a true monument. The distance of a monument from the parent plateau ranges from meters to kilometers.

Monuments are the result of external erosion by running water and mass wasting, and of weathering along joints and other fractures within flat-lying sedimentary rocks, generally in a plateau. Erosion gradually separates sections of the plateau from its parent mass. As weathering and erosion continue to shrink the margins of the plateau and detached outliers