Copyright 2001 by Glenn R. Morton. This may be freely linked to and freely distributed so long as no changes are made and no fee is charged. (home.entouch.net/dmd/erosion.htm)
Creationists are always claiming that erosion occurs very rapidly. In their model, it has to because long times taken to erode something will blow their time scheme out of the water. Austin writes:
“Regional unconformities do exist between some strata in Grand Canyon, but the evidence favors rapid erosion.” ~ Steven A. Austin, “Interpreting Strata of Grand Canyon,” in Steven A. Austin, editor, Grand Canyon: A Monument to Catastrophe, (Santee: Inst. for Creation Research, 1994), p. 52
So, lets look just a bit north of the Grand Canyon, where similar rocks were deposited and see how much erosion has taken place in 100 years.
One can see that very very little erosion has taken place at Bowknot Bend in Utah. A close examination of the original photo shows that some of the rocks in the foreground are identical today as to shape as they were 100 years earlier. Clearly erosion, even with a major river going through these channels, doesn't do much eroding in 100 years. Even in a thousand years (ten times what you see here), it doesn't look like much geologic work would be done to these rocks.
Given the tiny tiny difference between these two photos, one must wonder how long it would take to have eroded away the cliff material seen in the background. That rock, you must realize, used to cover the area and it was eroded away by this slow eroding river.
Think about this when you consider the erosion of 10s of thousands of feet of sediment like we see in the Appalachians and the North Sea.
The Appalachians see (home.entouch.net/dmd/appalach1.htm) this is from A. W. Bally, _Seismic Expression of Structural Styles, Vol. 3, AAPG Studies in Geology Series, #15, p. 3.4.1-82. There is about 10,000 feet of erosion from the reflector marked ‘bed a’ up to the horizontal line marked ‘unconformity’ :
At the Green River rates of erosion, it would take many millions of years to erode 10,000 feet off of the Appalachians.
The North Sea (see home.entouch.net/dmd/northseatime.htm)
There is 12,000 feet of erosion here in the Broad Fourteen Basin of the North Sea. Erosion doesn't happen at the rates YEC leaders claim. And, once again, YEC leaders never show their followers this kind of data.
Daddy, how long until we get there? This is the usual question of children in the back seat on a long trip. Bored, they can do no more than ask this much expected question--often over and over. Patiently, parents answer this question. This is normally where the issue ends. Children understand the logic even if they don't understand how long 2 hours can seem when you are bored out of your skull. But what if the conversation went like this:
“Daddy, how long until we get there?”
“Two hours.”
“Then that means we left the house two hours ago!,” your child beams with pride at this deduction.
Of course, as a parent you would fear you have a defective child. Such logic is highly flawed, indeed it is a non-sequitur. How far you have to go has no bearing on how long you have been traveling. You might have been traveling 20 hours with only 2 left but your young genius deduces from the fact that there are only two hours left that you couldn't have been traveling more than 2 hours! As a parent, you sigh and give up those dreams of your child winning the Nobel Prize in physics.
As clearly logically deficient as we see this illustration to be, it is precisely the logic behind a very often used (and amazingly convincing) young-earth creationist argument. It is the erosion argument.
In 1973, Steve Austin, writing under the pseudonym, Stuart Nevins (1974), published an argument for the age of the earth based upon the rates of erosion presently observed. He took the estimated mass of continental rocks above sea level (383 million billion tons) and divided it by the rate at which sediment is added to the ocean (27.5 billion tons/year). The result (14 million years), Nevins argued, is the maximum age that the continents could have existed. After 14 million years, the continents would be eroded to sea level. Thus, like they mythical child above, he illogically concludes that the earth must be young. He writes:
“The continents are being denuded at a rate that could level them in a mere 14 million years! Yet, evolutionary-uniformitarian geologists feel certain that the continents have existed for at least 1 billion years. During this supposed interval of time the present continents could have been eroded over 70 times! Yet—miracle of miracles—the continents are still here and do not appear to have been eroded even one time!” (icr.org/pubs/imp/imp-008.htm) See also Stuart Nevins, “Evolution: The Oceans Say No!” in Henry Morris, Duane Gish and George Hilstad, editors, Creation, (San Diego, Creation-Life Publishers, 1974), p. 164-172.
What I will show below is the lunacy of the logic displayed above. How long the continents have to go before they are peneplaned is irrelevant to how long they have been eroding. We will calculate how long it would take for the sediments eroding off of the to account for the amount of sediment seen in the Gulf of Mexico. I will say that the amount of sediment in the Gulf is truly astounding. I was manager of geophysics for the Gulf of Mexico for 9 years. I have seen gravity data which shows that along the Louisiana coastline there are 75,000 feet of sedimentary rocks. In the calculation below, I will use only about half that value as the average. I have seen seismic data which shows about 50,000 feet of sedimentary rock 200 miles offshore. So the numbers I am using are conservative for the Gulf. Yet creationists, ignorant of geology have actually claimed incredibly small numbers for the deltas. George McCready Price, the man who heavily influenced Henry Morris, stated:
“The actual depth or thickness of the deposits formed by modern deltas varies greatly, but is generally not very great. ‘The mud of the Nile delta is not over 10 or 15 meters thick.’ some of the deltas in Europe seem to be thicker than this, and that of the Ganges is about 20 meters. ‘The actual delta deposits of the Mississippi range from 9.5 to 16 meters near New Orleans, increasing to 30 meters at the head of the passes, beyond which the thickness rapidly increases.’” ~ George McCready Price, The New Geology, (Mountain View: Pacific Press Publishing Association, 1923), p. 147
Nothing could be further from the truth as we will see.
Two hundred million years ago the mouth of the Mississippi river was at Cairo Illinois, not at New Orleans, Louisiana. The Mississippi and other rivers had to fill in a huge amount of sediment which is now under dry land from Cairo Illinois down to New Orleans.
There are 1,588,604,000,000 sq. meters in the Gulf of Mexico. From seismic data and gravity data, I know that there is an average of 15,200 meters of sediment over this region. We have actually drilled through about 10,000 meters of sediment so that is indisputable. Now, 1,588,604,000,000 x 15200 = 24,146,780,800,000,000 cubic meters.
The Mississippi River carries about 210 x 10^6 tons per year. [see Scott M. Mclennan “Weathering and Global Denudation”, Journal of Geology, 101:2, p. 296)
That works out to be 210 x 10^9 kg per year. There are 2400 kg per cubic meter, so dividing we have 210 x 10^9 kg per year / 2400 kg per cm = 87,500,000 cubic meters per year. A good assumption is that the other rivers emptying into the Gulf probably are equivalent to another Mississippi River. Thus we will assume that 175,000,000 cubic meters per year are deposited.
Dividing this into the volume of the Gulf sediments we find 24,146,780,800,000,000 cubic meters/175,000,000 cubic meters per year = 137,981,604 years. That is 137 million years for the river to fill up the Gulf of Mexico.
Now, lets do something NO YOUNG EARTH CREATIONIST EVER DOES WITH THE EROSION ARGUMENT. Lets put all this sediment back on the Continent. The Mississippi River has a drainage area of 3.27 million square kilometers or 3,270,000,000,000 square meters. Assuming half of the sediment came from the eroded Mississippi drainage area we find that 12,073,390,400,000,000 cubic meters must be put back on the continent. Thus the continents were, 12,073,390,400,000,000 cubic meters / 3,270,000,000,000 square meters = 3692 meters higher before the Gulf was filled in. That means that about two miles of sediment has been eroded off the continents. Does that mean that the continents were 3692 meters higher above sea level back then? NO. The continents sink into the mantle of the earth if you add weight to them. The ratio is about a third of the extra height of sediment is the amount the sediment sinks. Thus if you add 3692 m of sediment the continents sink about 1200 m, leaving the continent only about 2400 meters higher. Thus one can't say that this much sediment is too much.
The Mississippi has been in its present place for about 200 million years. Why 200 rather than 137? Because some of the sediment was deposited in the Jurassic at Cairo Illinois was then re-eroded and deposited in Arkansas, where it was then re-eroded and moved to Louisiana, where it is now being re-eroded and put into the Gulf. The net sediment influx is smaller over the past 200 million years than what we see today. This is true both because of re-erosion as well as in the past the Mississippi's drainage area was much smaller so that it carried less sediment. Today the Mississippi erodes from Arkansas. 200 million years ago, Arkansas was under water and thus couldn't be eroded.
The Nile river presents similar problems for the young-earth creationist. Five million years ago the Nile cut a huge canyon which is 3.5 kilometers deep that lies under Cairo. This was when the Mediterranean was a dry desert with salt and desert dunes found at the bottom of that sea. After the sea waters re-filled the Mediterranean, the Nile spent the next 5 million years filling up this canyon. Only in the last million years has the delta actually begun to protrude from the African coast. (we see the channel on seismic data). Here are the calculations:
The volume of Nile sediments in the canyon (determined by measuring the width and depth of the canyon from seismic data) is 200 x 10^12 cubic meters (Rushdi Said, “The Geological evolution of the River Nile,” in Fred Wendorf and Anthony E. Marks, Editors “Problems in Prehistory: North Africa and the Levant,” (Dallas: Southern Methodist University, 1975), pp 7-44, p. 15).
The Nile River inputs 121 x 10^9 kg of material per year to the delta. That works our to be 50,500,000 cubic meters per year (121 x 10^9 kg/ 2400 kg/m^3). [see Scott M. Mclennan “Weathering and Global Denudation”, Journal of Geology, 101:2, p. 296)
Dividing these two numbers we have 3,960,396 years for the length of time it took for the Nile, with observed depositional rates to fill up the canyon. Thus the delta, which protrudes from the African coast started about 1 million years ago. The Nile has been in place for about 5 million years. This is consistent with radioactive dating of the time of formation of the canyon.
The Scottish Highlands are relatively low when compared with other mountain ranges around the world. They are old, having been uplifted during the Ordovician over 400 million years ago. Using the logic of the creationists, we would calculate that because they are low and could be eroded in less than 14 million years, that they can't be older than that. So the question is, is there any evidence that the Scottish Highlands have been eroded for this long (or longer)? There is.
Much of the sedimentary cover in the highlands has been eroded off. Igneous rock is all that remains--granite, granitic batholiths, etc. But how much has been eroded off? It is possible to tell by looking at the mineral which are found in the granites. Some minerals require high temperature and pressures in order to form. We find this to be the situation when looking at the igneous rocks of the Scottish Highlands. On the west coast, Near Scourie, Scotland the minerals observed formed between 35 and 50 kilometers deep! (R. A. Strachan, “Early Earth History and Development of the Archaean Crust,” in Nigel Woodcock and Rob Strachan, editors, Geological History of Britain and Ireland, (London: Blackwell Science, 2000), p. 49)
What this means is that the rocks above them have now been eroded off. How many years would this take? It is often cited by creationists that the erosion at 1 inch per thousand years can lower the continents in 14 million years. Using 1 inch per year it would take between 1.2 and 2 billion years to erode the highlands to that depth. Interestingly, the radiometric age for these rocks is 2.7 billion years old. Given the lack of knowledge about the rate of erosion, this is amazingly close and granite is very hard so the rate of erosion may be lower than 1 inch per thousand years.
Conclusion
Like the child above, the erosion argument confuses how far one has to go with how far one has already traveled. The illogic is clear to all but the young-earth creationists.
Glenn Morton
Dec 6,2003
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