So the world is young

Year by year, rain, wind, frost and waves are eroding soil and rock from our continents and dumping them into the ocean. Gullies, gorges and canyons are growing. Coastlines are disappearing.

Scientists have estimated that some 20 billion tonnes of sediment are disappearing each year.1,2, 3   Eventually the fine material builds up as soft layers of mud on the hard, black, volcanic sea floor.

Surveys indicate that the average depth of all the sediment on the ocean floor is less than 400 metres.4   Some large areas of the ocean floor have hardly any mud at all.5  If the oceans are billions of years old why is there not more sediment?

Perhaps the creeping of the ocean floors by plate tectonic movement, at a few cm per year, is forcing the sediment deep inside the earth via the ocean trenches, also known as subduction zones. But that would only account for one billion tonnes of sediment a year.4 The remaining 19 billion tonnes per year would accumulate the total seafloor sediment in less than 12 million years.  Sediment and mud should be choking the oceans, but it is not there….


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