Young-earth "proof" #15: Continents are eroding at a rate which would bring them to sea level in less than 14 million years. Inasmuch as the continents are anything but flat, the earth cannot be billions of years old. (27.5 x 10^9 tons sediment/year are lost to the oceans by erosion; the present mass of the continents above sea level is 383 x 10^15 tons.)
Article by Dave E. Matson on the Secular Web site. Also available in the TalkOrigins Archive.