Note 1 — Chapter I · MESA LAND

“Mesas appear to furnish the most direct and convincing testimony we have of the tremendous power of the wind in effecting general erosion under conditions of aridity. That water could not possibly produce such effects is shown in a number of ways. On the continental divide the streams are smallest. Drainage features are necessarily insignificant. Rainfall is the scantiest. These summit plains of the continent are a region of continual high wind and constant sand-storm. By wind action alone there appears to be incontestable testimony that from the entire area of the vast arid region there has been lifted and exported in very recent geologic times a prodigious layer of rock not less than 5000 feet in thickness. Thus it is that arid regions have introduced us to an erosive agent more potent than stream-corrosion, more constant than the washing of rains, more extensive and persistent than the encroachments of the sea.”—Charles R. Keyes, Wind-Graved Mesas and their Message.