THE WIND'S EFFECT UPON TOPOGRAPHY.

Oamaru Mail, Volume XXXIX, Issue 10957, 23 December 1911, Page 1 (Supplement)

THE WIND'S EFFECT UPON TOPOGRAPHY.

In a recent number of Science, Professor Charles R. Keyes, the well-known geologist, makes some very interesting observations as to the probable origin of the present topography of that vast stretch of country lying east of theRocky Mountains, which the geographies used to characterise as the Great American Desert, and which nowadays we commonly speak of as the Great Plains. Professor Keys points out that the imagination of "the geologist has run riot iu attempting to explain the existence of ths vast level territory. In fact, ho says, the varying explanations reflect "a century's, trend of sediirnentative and physiographic thought in America." One explanation has been that the plains represent a normal deposit afc the bottom of the ocean, prior to the vast upheaval that produced the continent; another that the strata that underlie the plains were laid! down >"n great interior lakes; and yet another that they were built up of sediment carried by rivers in a. way that corresponds on a large scale to the formation of the delta of the Mississippi. "To these hypotheses," says Profes-, sor Keyes, "must now be added a fourth —that of eola.tive planation," — that is to say, the levelling action.' of the winds. "In the extreme West n front of the Rocky Mountains," Professor Keyes continues, "is a belt oi deflation where often the substructure forms a typical rock floor. In the broad medium belt, eolian (wind) deposit to a vast extent has taken place, and is still going on. In the Eastern belt, along the Mississippi River, wind effects, although extensive, are almost wholly obscured by moist-chmate phenomena. "The two essential points to be noted here are: First, continental deposits may be as important as marine or lacustrine deposits; and, second, that on the American continent eolic deposits are being formed under conditions whereby they may be preserved effectually through the geologic ages." Professor Keyes declares • that the geologists of tonlay are .finding in the action, of the winds an explanation of" many geological formations that until recently were attributed to the action of water. At the present time, he'says, the geological formations that receive the greatest attention are those continental deposits, or stretches of earth laid down' and preserved on land instead of in lakes or seas. New interest is being aroused in these sub-aerial formations, -.particularly in the great plains and their deposits, inasmuch as these appear to introduce on a grand scale a mode of geological formation hitherto almost ■unrecognised. "Continental deposits thus begin to assume an importance which has never before been accorded them," declares Professor Keyes. And he does not hesitate to predict that the theory of "eolic planation" and deposit, or levelling by the action of the wind, "protnises to be one of the half-dozen great aiid novel thoughts of our country in the domain of geology." ■• As Professor Keyes is one of our foremost authorities oh structural geology, what he says as to the new view' of the. origin, of .the plains is sure" bo command wide attention;