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Planation surfaces are not to be confused with other flat surfaces of different origin.
An erosion surface is defined as: “A land surface shaped and subdued by the action of erosion, esp. The term is applied to a level or nearly level surface.” Some planation surfaces are extraordinarily flat (figure 1).The origin of landforms in geomorphology is in such disarray that after 200 years, scientists cannot even provide a credible hypothesis for the geomorphology of southeastern England—an area where the science of geomorphology first developed.Geomorphologists still hope that someday they will be able to understand the origin of landforms by studying all these observable processes, of course thinking in strict uniformitarian terms.The definition includes erosion by water because many surficial erosion and planation surfaces are capped by a veneer of generally rounded rocks—rounded by the action of water. Top of the planation surface in the western Cypress Hills.This surface is capped with an average of about 23 m of well-rounded quartzite gravel and boulders from across the continental divide, over 400 km away. Lake Missoula flood bar along the Snake River, Washington, west of Little Goose Dam.