We have had 50+ ice ages, and we are now coming out of another one, which is being sped up by the increased average ice melt since the beginning of the industrial revolution roughly 150 years ago (If the planet heats up enough to cause, oh let's say...a big enough chunk of ice to break off from the south pole and fall into the ocean; the tsunami wave would be enough to wipe many of us out) -- I refute geologists who say the Grand Canyon was caused by merely uplifting land, and increased gravitationally influenced water erosion -- that is only half the answer...Why is the valley floor not raised by all the falling debris? Take into account the torrents of water which have -- at the end of each ice age -- repeatedly rushed down out of the Rocky Mountain range, into places like Grand Canyon and Sedona, Arizona etc etc etc -- QUESTIONS: If intermontane basins between ranges like those found in nevada are back-filled with great amounts of rock debris descending downslope, so that the valley floors move upwards as the ranges wear down > go to: http://rst.gsfc.nasa.gov/Sect6/Sect6_8.html > why is the grand canyon valley floor not moving upwards as well from all the rock debris descending downslope?