Ok, so I was having a little spat with a YECist on another site, and I went to check some stuff on Answers in Genesis and I found this argument, I'm hoping somebody that understands geology can weigh in on this, as I'm now determined to refute it but I don't know enough about geology to do so. It's not my thing you see.
4. Not enough mud on the sea floor.
Rivers and dust storms dump mud into the sea much faster than plate tectonic subduction can remove it.
Each year, water and winds erode about 20 billion tons of dirt and rock from the continents and deposit it in the ocean.6 This material accumulates as loose sediment on the hard basaltic (lava-formed) rock of the ocean floor. The average depth of all the sediment in the whole ocean is less than 400 meters.7 The main way known to remove the sediment from the ocean floor is by plate tectonic subduction. That is, sea floor slides slowly (a few cm/year) beneath the continents, taking some sediment with it. According to secular scientific literature, that process presently removes only 1 billion tons per year.7 As far as anyone knows, the other 19 billion tons per year simply accumulate. At that rate, erosion would deposit the present mass of sediment in less than 12 million years. Yet according to evolutionary theory, erosion and plate subduction have been going on as long as the oceans have existed, an alleged three billion years. If that were so, the rates above imply that the oceans would be massively choked with sediment dozens of kilometers deep. An alternative (creationist) explanation is that erosion from the waters of the Genesis flood running off the continents deposited the present amount of sediment within a short time about 5,000 years ago.
So, anybody got any opinions on that one? I suspect that they counted loose sediment without noting that it is compressed into rock, but I don't know.
Edited by Adminnemooseus, : Added the "(Sea floor sediment accumulation)" part to the topic title.
Set up as an ideal the facing of reality as honestly and as cheerfully as possible. -Dr. Karl Menninger Repetition does not transform a lie into a truth. - Franklin D. Roosevelt
Good catch on the compression – that's one part. Also, note that "The main way known to remove the sediment from the ocean floor is by plate tectonic subduction" is not substantiated, 'cause it's not true. And, of course, the uniformitarian assumption that they decry so strongly when it suits them.
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.
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.
When you next discuss this, you might ask how your YEC friend explains the variation of thickness of sediment on the ocean floor; e.g. zero at the Mid-Atlantic Ridge, about 150 million years worth at the margins of the Atlantic, and pretty smooth variation in between. Exactly as predicted by slow plate spreading at the ridge over millions of years.
quote: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.
Actually, it's an unsolicited claim by Humphreys in response to nothing in particular. So it's his responisbility to be familiar with the theory he's critcising. He isn't, or he's suppressing relevant information.
quote: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.
Cuts both ways. In the absence of rate information (and I don't know if there is no rate information; I wouldn't accept the anonymous author's word), nobody can estimate the effect of the processes. Especially Humphreys can't. So his claim that there's too much sediemnt is unfounded. Given the vast amount of other evidence for an old Earth and slow tectonic processes, the best Humphreys can come up with is "not proven for this particular process". Yet he claims proof.
quote: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.
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.
The reference to whic they link is irrelevant.
No calculations are presented or refered to in support of the numerical claims. That is, they appear to be made up out of thin air.
Oh, and mainstream science doesn't claim that the oceans are anywhere near three billion years old; Isaak explicitly pointed that out, the reference linked to from your reference shows it clearly. There have been oceans for many billions of years, but that's something else entirely.
The question they raise is that there is not enough mud on the sea floor. It is a classic example of how the leadership in Biblical Christianity and Biblical Creationism con the gullible public, of the dishonesty of Biblical Christian Leadership.
First off, they make the assumption that "seas" are those we are familar with today.
That is of course, patently false, demonstrably false, and frankly, the "Creation Scientists" know that and just lie to the public.
We can identify many ancient oceans. For example, the summit of Mount Everest, the lowest exposed layers of the Grand Canyon, all of central North America, the Sahara Desert, the Gobi Desert, and quite frankly, a significant part of all the land we live on are the very sediments that they say are missing.
Subduction is a force that removes evidence. Those areas that do get subducted are then melted and eventually return to the surface as magma.
Yet according to evolutionary theory, erosion and plate subduction have been going on as long as the oceans have existed, an alleged three billion years.
Possibly true, at today's erosion rates. That would be "erosion rates with mechanized agriculture and forestry stripping huge swaths of land nearly bare-nekkid." I don't have numbers at hand, but I would be very unsurprised if current erosion rates are many times the rates of just 200 years ago.
Even if science didn't know where all the mud went to, that still wouldn't say anything in favor of the creationist model. What I mean to say is that not only is the claim wrong, it's also (and in my opinion - more importantly) irrelevant.
I was just curious, that's all, I wanted to understand what they were saying and WHY it's wrong, I already figured it was wrong, but I wanted to know why. I didn't want to just say they are wrong because it's Answers in Genesis saying it, that's not a terribly scienitific way of deciding something is wrong.
don't forget, you can have sediment buildup at subduction zones. granted, it's a touch wierd, but . . .
you know those mountains on the west coast of california (not the sierra nevada, the other ones)? those are essentially the result of the destruction of the farallon plate (the san andreas transform fault used to be a subduction zone). When plates collide, the sediment doesn't just get subducted, but can build some mountains).
ah, should add, the sierra nevada is from the collision, the extra mountain range is from the sediment. did I confuse people yet?
you know those mountains on the west coast of california
Just a smidgen, having gone to HS and JC there, where I studied biology and geology.
If you want to know where all that marine mud went, go walking around the Morro Bay area after a good rain, chances are it is a few inches thick sticking to the soles of your shoes.
The coast range has one of the most complex jumbles of geologic formations in the world, which is testimony to its history as a plate boundary and an accretion zone. Sure glad field camp was in the Zuni Mountains of New Mexico instead of the Coast Range or I'd probably still be there trying to get that 6 units of credit.
At any rate, what previous posters have said is true, much of the ocean sediment is now continent and/or compressed beyond any YECs imagination.
Well of course there are no references in the original argument so it's impossible to check the numbers. But it assumes that subduction is the only process that removes sediment from the ocean basins. But subduction of sediments is actually fairly insignificant. The numbers sound right; about a 20th of all sediment being subducted. And once it's subducted you never see it again, except in it's geochemical signature in arc magmas. But California's Great Valley has over 50,000 feet of sediment that was never subducted. The stratigraphic thickness of sediments exposed in the mountains of the western U.S is substantially more than this. The total stratigraphic thickness of sediments deposited and then metamorphosed to form the Appalachians is staggering to even imagine. Accretion (that is closing of ocean basins, scraping off sediment, adding it to the continent) is the primary plate tectonic process that removes sediment from the ocean basins.