If sediments have been accumulating on the seafloor for three billion years, the seafloor should be choked with sediments many miles deep. Every year water and wind erode about 20 billion tons of dirt and rock debris from the continents and deposit them on the seafloor (check the pic below). Most of this material accumulates as loose sediments near the continents. Yet the average thickness of all these sediments globally over the whole seafloor is not even 1,300 feet (400 m)!!! (WHAAAAT?) Some sediments appear to be removed as tectonic plates slide slowly (an inch or two per year) beneath continents. An estimated 1 billion tons of sediments are removed this way each year. The net gain is thus 19 billion tons per year. At this rate, 1,300 feet of sediment would accumulate ---> in less than 12 million years
Posted on: Tue, 30 Dec 2014 19:33:56 +0000
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