Much more sediment is deposited than removed by subduction (Talk.Origins)
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- 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.
CreationWiki response: First of all the wording of the above claim is not an accurate representation of Russell Humphreys's article, in fact the last phrase, "not the hundreds of millions of years that the oceans have been around." was clearly not written by a Young Earth Creationist. It states the 100's of millions of years as fact, but a Young Earth Creationist would say something like alleged 100's of millions of years as Humphreys actually does. By the way Humphreys cites the age of the oceans alleged by evolutionist at 3 billion years not 100's of millions of years (Talk.Origins quotes in blue)
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.
The reference to subduction is a response to a claim by an evolutionist that subduction did remove it. So at this point Humphreys is simply dealing with the only mechanism the evolutionist had given him at the time.
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.
Fine - but what is the average rate per year at which these processes occurs? Without an estimate of the average rate per year at which they occur, there is no way to estimate their net effect.
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.
According to Uniformitarian theory, over the last 12 million years this effect would account for at most 1% of the total. This stretches it only to 12.12 million years. In other words this effect is insignificant to the problem.
- Reference:Continental Drift
The simple fact is that for the oceans to be 3 billion years old the average accumulation of mud would have to be only 96 million tons per year. This means that the methods of removal suggested in point number 1 would have to remove on average 23.9 billion tons of mud per year.