OCR Text |
Show HOW NATURE REMOVES THE SURFACE OP EARTH Investigations by thft United Stales Geological Survey of tho erosion of numerous nu-merous drainage basins of tho United States show that tho surface of tho country coun-try Is being removed at tho average rate of about an Inch In 7G0 years. Though this amount seems trivial when spread over the surface of tho country. It bo-comes bo-comes stupendous when considered an a. total, or even In separate drainage basins. Mlsslsfllppl river, for Instance, carries annually to the sea 136,400,000 tons of dissolved matter and J540.50O.O0O tons of suspended mattor. and of this total Ohio river carries 83.350,000 tons and Missouri Mis-souri river contributes more than twice as much. Colorado river, which has built up for itself a vast delta, brings down more suspended matter than any other river In tho United Slates, delivering deliv-ering annually 3S7 tons for each square mllo of Its drainage bttHln, or a total of 100.740.000 tons. Tho rivers of the United States carry to tidewater every year 270,000,000 tons of dissolved matter and 513.000.000 tons of suspended matter. This total of 783,-000,000 783,-000,000 tons ropreaenls more than 350,-000,000 350,-000,000 cubic yards of rock, or 610,000,000 cubic yards of surface sol). If this erosive ero-sive action had been concentrated on the Isthmus of Panama at tho tlmo of American Ameri-can occupation It would have 'excavated tho prism for an SB-foot level canal In about sovonty-threo days. |