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Author Topic:   Deposition and Erosion of Sediments
Percy
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Posts: 20959
From: New Hampshire
Joined: 12-23-2000
Member Rating: 3.1


Message 28 of 127 (192111)
03-17-2005 10:18 AM
Reply to: Message 24 by Faith
03-17-2005 4:08 AM


Hi Faith,

There was a lot in your post, but I'm just going to focus on one small point:

Faith writes:

My problem is with the enormous time frame. The idea that ANYTHING could sit still for 50 million years is simply preposterous to my mind. How can ANYTHING "subtle" happen in a 50-million year period? Hurricanes alter seacoasts and beaches, tornados move tons of stuff from here to there, one good rain causes mudslides all over California that rearrange local landscapes drastically, not subtly, and destroy houses; all in one year; but the redwall limestone stays in place for 50 million years even in the phase where it's quietly sedimenting away and not yet lithifying?

You use the example of the Redwall Limestone layer of the Grand Canyon, so I'm going to focus on that. This layer represents what was once a shallow sea. We can tell by the makeup of the sediments that it was a shallow sea, and it persisted for a long time, perhaps longer than 10 million years. We know that it existed about 340 million years ago by radiometric dating.

The catastrophes that are so devastating on land often go unnoticed under water. The hurricanes, tornados, rains and mudslides that you mention have impacts that are felt primarily on land. Hurricane Andrew devastated southern Florida in 1992, causing billions of dollars worth of property damage, yet if you had visited the ocean floor some miles off into the Atlantic after that hurricane you would have found no sign of it at all.

The redwall limestone layer of the grand canyon does not happen to include the shoreline area of this shallow sea. The massive amounts of sediments that would have been recorded near shorelines after major storm and flood events have no effect far away from shore. Out in the middle of this quiet sea sediments slowly accumulated undisturbed eon after eon.

There are many examples of the accumulation of sediments over time - every ocean is another example. The floor of the Atlantic ocean forms at the mid-oceanic ridge at the rate of about 10 cm per year. The ridge goes pretty much north/south through the center of the ocean - it goes right through Iceland, accounting for its volcanic activity. Sea floor near the ridge is very young, while sea floor near the American, European and African continents is very old. Sea floor cores taken of sediment near the ridge are very shallow before hitting rock, while sedimentary cores taken near continents are deepest. This is because sediments gradually accumulate over time, and in general the oldest sea floor will have the greatest amount of deposited sediment (it also depends upon sediment sources, of course).

The ultimate fate of all sea floor is subduction beneath continents (continental crust is lighter than sea floor crust, so sea floor always subducts beneath continents). While there are continental rocks in some places that are billions of years old, there is no sea floor anywhere in the world older than 200 million years. The only record we have of seas and oceans older than that is those that were pushed up by tectonic forces and became part of continents, such as large areas of Arizona. The Grand Canyon is unique in that it provides visibility to the layers that underlie Arizona, but it is important to keep in mind that these layers extend for miles and miles in all directions, you just can't see them.

--Percy


This message is a reply to:
 Message 24 by Faith, posted 03-17-2005 4:08 AM Faith has not replied

Replies to this message:
 Message 31 by Minnemooseus, posted 03-17-2005 1:22 PM Percy has replied

  
Percy
Member
Posts: 20959
From: New Hampshire
Joined: 12-23-2000
Member Rating: 3.1


Message 33 of 127 (192147)
03-17-2005 1:55 PM
Reply to: Message 31 by Minnemooseus
03-17-2005 1:22 PM


Moose writes:

The only record we have of seas and oceans older than that is those that were pushed up by tectonic forces and became part of continents, such as large areas of Arizona.

I think you threw out a clinker here.

I think your sea deposits in Arizona are from sea transgressions onto the continents. The deposits were always continental, not from the ocean basins.

Oh, okay, that makes sense. Thanks for the correction.

I don't think this affects my arguments, though. The Redwall Limestone layer revealed at the Grand Canyon is from a shallow sea not much exposed to the vagaries of the weather above its surface nor of the distant shores.

--Percy


This message is a reply to:
 Message 31 by Minnemooseus, posted 03-17-2005 1:22 PM Minnemooseus has not replied

  
Percy
Member
Posts: 20959
From: New Hampshire
Joined: 12-23-2000
Member Rating: 3.1


Message 37 of 127 (192163)
03-17-2005 4:40 PM
Reply to: Message 35 by Faith
03-17-2005 2:14 PM


Re: Proposal
Faith writes:

There have been proposals by some on other threads that only one or two of you answer me at once. Could you somehow agree among each other who should have the job of taking down the crazy creationist and the rest just not post on this topic until some further point to be decided on later? I simply can't handle it all.

I'm very sympathetic to this issue. As someone else already mentioned, a Great Debate thread is one way to limit the number of participants. We could nominate our "champion" and he could challenge you and your slingshot. :)

One might ask why you're attracting so many responses, and I can answer by way of example. Imagine if I were to go to a Christian forum and begin arguing that Jesus was baptized by Herod the Great and that Paul was his first apostle. In no time at all that thread would attract a ton of responses as people tried to correct my misimpressions. And that's why you're attracting so many responses. Whether or not they're correct about you, to many people you look like the victim of a number of simple misimpressions, and they all want to help.

Independent of whether the flood of Noah really happened, there is a field of science known as geology that has systematically studied for a couple of centuries now how sediments are layed down (among many other topics). That's not to say that makes them automatically right, but it does mean that the issues have been pretty thoroughly thought through. Arguments from personal skepticism (e.g., "I just can't believe a sea could exist relatively unchanged for millions of years") or ignorance (e.g., "In the Grand Canyon the real erosion is the canyon itself") cannot possibly carry the day against so well established a field.

Understanding what geology actually says about sedimentation and erosion does not mean you have to accept it, but you have to understand it before you can effectively argue against it. We already know you don't accept it, but if these threads have taught us anything at all it's that you don't understand what it is you're rejecting. The approach you're taking isn't, "I've studied and learned the relevant principles of geology, and I reject them because of X, Y and Z." You're instead reasoning that since geology is in league with evolutionists (e.g., "geologists are in thrall to the false evolutionistic theory"), they must be wrong, and so you cast about to and fro searching for valid counterarguments. Such flailing is unlikely to be successful.

I can tell by some of your posts that you're sincerely attempting to study and understand the issues. I urge patience. If geologists are wrong then the better you understand their evidence and arguments, the better you'll be able to pinpoint the errors. But if you continue to rush the discussion all you'll get is a lot of, "No, no, geology doesn't say that at all."

--Percy

PS - The above quotes of you are only intended as paraphrases, but I think they accurately capture your point of view.


This message is a reply to:
 Message 35 by Faith, posted 03-17-2005 2:14 PM Faith has replied

Replies to this message:
 Message 38 by Faith, posted 03-17-2005 5:50 PM Percy has not replied

  
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