If the rocks are so old then why haven't they eroded?

Question

According to sedimentologosts the average height reduction for all the continents of the world is about 60 mm per 1,000 years.
In other words, a height of 150 kilometres (93 miles) of continent would have eroded in 2.5 billion years. If erosion had been going on for billions of years, no continents would remain on Earth.
So how come evolutionists can claim that rocks are billions of years old?

People seem to be missing the point!
The rocks in Britain, say, are alleged to be millions of years old, and so far as I am aware evolutionists think they have been above the sea for millions of years. (Some rock must have been to allow for allaged evolution of land animals.)

So the point is why hasn't the exposed rock eroded (many times over!)

Answer 1

Plate Tectonics. The reason the rock erodes is because it has been elevated. (If you notice, the seafloor doesn't see much erosion.) Uplift didn't just happen once, it is still going on today. Look into elevation changes from major earthquakes like the Good Friday Earthquake in Alaska. In a matter of minutes, large areas of the land were pushed up several yards. Right there (in a few minutes of shaking) is several thousand years worth of material to erode.

Biological Sciences (like evolution belongs to) don't generally depend heavily on erosion rates to support their work, so pointing your question in their direction is a little unusual. It also makes it look like you have some other agenda beside finding accurate information.


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For your added details section... They have eroded. Had they not, the land there would be thousands of feet higher.

If it were like it seems like you are trying to suggest, the rock at the surface should all be the same layer, right? Or are you just arguing that the rate of erosion is for some reason much, much faster than what we have observed? But still, this is not a critical component of any major scientific theory, especially evolution. Why do you keep presenting what seems like a strawman argument regarding evolution?

If it is indeed a strawman argument, it would be sad indeed if you could not defeat it with a better explanation. Maybe you should try to provide one instead of just vaguely questioning the accepted one.

Answer 2

Some rocks made up out of eroded rock. Sedimentary rocks like sandstone are. Sand is grains of minerals, mainly quartz, that have eroded off of rocks. The sand has then gathered in thick layers exposed to great pressures and cemented togheter to form new rock. Also sediment layers are continually subducted into the earths mantle through tectonics. The sediment is then molten to again form new rock.

So everything is recycled. Erosion doesn´t destroy the rocks. It just moves it. But the very old rocks you speak of are rocks that for whatever reasons have not been destroyed by either erosion or tectonics. They should be gone. And they almost are so you are partly right. None of the earths primordial crust remain. There are only a few places on earth where very old rock remain.

-edit-
The rocks in Britain are what is left after erosion. Serious erosion. The Scotish highlands and the Scandes (northern Norway/Sweden) were once connected. The have since drifted apart. But once upon a time, HUNDREDS of millions of years ago they were a mountain range on the same scale as the Himalayas... THAT is erosion. Countless iceages have worn these mountains down to the stumps they are today. Mountains can only exist where there is plenty of geological activity to keep pushing them up as they are worn down.

Answer 3

Evolutionists study the origins of life. Not the age of rocks. Geologists do that.

You do realize that 60 mm is small and that that figure breaks down to .06 mm a year. That's like 3 strands of a human hair a year.

Also, erosion continues, but so does deposition. So yes a lot of erosion has happened. But a lot of deposition has happened too. That deposition is mostly made of what has been eroded. As does igneous rock body intrusion and extrusion. They continue to form as well. Earth is dynamic. New rocks are forming all the time at the spreading centres and volcanoes, etc. (look up plate tectonics).

You also have to take into account isostatic rebound. Using Airy's theory, continents are underlain by a root that "balances" them in the mantle. As the continent weathers, it becomes lighter and the root underneath rises and pushes up the continent. So a weathering of 2 m might really only look like half a metre after isostatic rebound (just a guesstimate, I didn't use the formula but you get the picture).

Answer 4

Yes, there is a miscomprehension of the process implicit to the question, mostly addressed in earlier answers. Just to add, one of the problems with your estimation is that you consider this erosion to occur equally at all places, and this is completely untrue. Most of the earth's surface is experiencing accumulation of sediment from the erosion of a much smaller area of elevated land. And in fact, we geologists have identified a number of places on the surface of the earth where the erosion you describe has removed many kilometers of rock through time, leaving just the originally deep heart of the mountains for us to see today.

But by happenstance, you have hit upon one of the primary difficulties faced by geologists in trying to understand the history of the earth. In effect, the further back in time you wish to find evidence, the harder it becomes because more and more of the rock around at that time has been eroded. Younger rocks, of the order of 500 million years or less are easily found and examined. Older rocks, on the order of 2-3 billion years old, are only found in a few dozen particular localities on the earth surface. There is essentially no rock that dates from the first 500 million years of the earth's history that has not been subsequently affected by erosion and-or metamorphism.

Answer 5

Dear Chas Chas,

Please, you must get yourself a basic geological education and try and grasp the essentials of this science, and what geologists are really trying to say. You must pose your questions from an informed standpoint, even if you don't agree with their conclusions. I'm sorry to say that most of what you say in about geology this question (and numerous other questiions and answers) is simply wrong.

Continents (and the rocks which compose them) are "recycled" over millions of years - the well-known processes of plate tectonics: subduction of crust, re-formation of crust via vulcanicity, uplift and erosion. However, there is no such thing as an "average" rate of subduction, uplift, erosion or anything in geology. The margins of continents are often repeatedly deformed, resulting in complex mountain belts, for example the Alps (on the collision zone between the African and European plates) whilst the centres of continents are rigid and highly stable (eg. the ancient Archaean rocks of Finland, canada, etc).

As a result, some areas of rocks have been exposed to erosion not once but many times; other thick sedimentary basins have been subsiding for very long periods of time and have never been eroded.

Geologists can clearly see on seismic data profiles where the sedimentary basins are, and where the uplifted and eroded rocks are. These seismic interpretatons are verified by thousands of boreholes. The erosion is often marked by truncation of strata beneath unconformities, and the resulting former erosion surfaces are clearly onlapped, or draped, by younger strata . Geologists use all this to predict, with great success, where oil-bearing strata might be found.

If you are still in doubt as to whether multiple phases of erosion have happened, then consider this: Relatively young (Tertiary age) Sedimentary sandstone rocks buried kilometres under the North Sea contain specific mineral assemblages, including well-rounded (i.e. eroded, weathered) grains of garnets, zircons, apatites. These minerals can be correlated with 100% accuracy on geochemical grounds to certain ancient Dalradian (pre-Cambrian) rocks in the Scottish Highlands, from where they were sourced via erosion. Not only that, but the mineral assemblages in the Tertiary sandstones vary according to the sequence of erosion (or "unroofing") of the Scottish highlands.

One other thing: "Evolutionists" (whatever that might mean) do not make claims on the ages of rocks, billions of years or otherwise. Geologists use fossils to put the rocks in their correct relative sequences according to the fossils contained within, and then use radiometric techniques to provide estimates of absolute ages. Please don't reply that this is a circular argument - it is not!

I'd be happy to engage in an intelligent off-line discussion if you wish - please post a reply and I'd be happy to forward my email address.

Answer 6

Rocks that haven't been exposed to the elements don't erode like surface rocks, another factor is new rocks are still forming today from low places where settling of sediments occurs. Thats why we have new rocks and old rocks.

Answer 7

Well they do erode, but then they are reformed into sedimentary and metamorphic rocks that are uplifted and the whole cycle starts again. Volcano deposit igneous rocks form deep within the crust which are also eroded.

Answer 8

wow you destoryed darwins theory.
actually rocks only erode when aggrevated by water wind and other forces. there is also sedimentary dust that builds it up, lave from bvolcanos and a constant shifting of the under earths core, we are moving both ways simultaneously

Answer 9

The earths surface is continually being reshaped and renewd by a proccess called Plate Tectonics

http://en.wikipedia.org/wiki/Plate_tectonics

Answer 10

sedement would form into rock in the ocean... thus building the continent out further, even with erosion.. plate tectonics are key too.