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Index to Creationist Claims,  edited by Mark Isaak,    Copyright © 2004
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Claim CD220.1:

About twenty-five billion tons of sediment are deposited in the ocean each year, but plate tectonic subduction only removes about one billion tons per year. Currently, ocean sediment thickness averages 400 meters. At the observed deposition rate, it would accumulate in only twelve million years, not the hundreds of millions of years that the oceans have been around.

Source:

Humphreys, D. Russell, 1999. Evidence for a young world. http://www.answersingenesis.org/docs/4005.asp or http://www.rae.org/yworld.html

Response:

  1. Yes, more sediment is deposited in the oceans than is removed by subduction. However, subduction is not the only fate of sediment deposited into the oceans. Some sediment deposited on the continental margin can become part of the continent itself if the sea level falls or the land is uplifted. Some calcium and organic sediments become biomass or ultimately dissolve. Some sediment becomes compacted as it deepens, so its volume is not indicative of the original sediment volume. Some sediment is "scraped" off of subducting plates and becomes coastal rocks.

  2. The uniformitarian assumption in the claim is not valid. Tectonics involves ocean basins forming and spreading, but it also involves them closing up again (the Wilson cycle). When the basins close, the sediment in the oceans is piled up on the edges of continents or returned to the mantle. Much of British Columbia was produced when the Pacific Ocean closed a few hundred million years ago and land in the ocean accreted to the continent.

Links:

Thomas, David E., 1998. "Creation physicist" D. Russell Humphreys, and his questionable "evidence for a young world". http://www.cesame-nm.org/Viewpoint/contributions/Hump.html

Further Reading:

Fichter, Lynn S., 1999. The Wilson cycle. http://csmres.jmu.edu/geollab/Fichter/Wilson/Wilson.html
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created 2000-7-3