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Show Erosion's Heavy C. it Erosion lias modified the surface of the earth more than the combined activities of volcanoes, earthquakes, tidal waves, tornadoes, and all the excavations of mankind since the beginning be-ginning of history, says the United States Department of Agriculture. The fact that it proceeds slowly, usually us-ually taking a thin layer at a time, does not in the least alter the impoverishing im-poverishing effects of erosion, speeded speed-ed up by man and operating through long periods of time. |