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Author Topic:   Limestone Layers and the Flood
Percy
Member
Posts: 22392
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.3


Message 110 of 128 (299560)
03-30-2006 8:50 AM
Reply to: Message 106 by jar
03-29-2006 8:43 PM


Re: One small question.
jar writes:
I was under the assumption that most limestone was originally made of the bodies of diatoms and other similar sized critters. IIRC they are really, really small critters, but often the limestone layers are hundreds to thousands of feet thick. Is that correct?
Edge or Rox are probably better suited to answering this question, but my understanding is that sedimentary limestone layers are formed from a combination of the following:
  1. The skeletal remains of microscopic creatures known collectively as coccoliths, a type of algae.
  2. The same remains but after having passed through the digestive systems of other creatures such as coral or some fish.
  3. In some waters the concentration of calcium carbonate in the sea water is high enough to precipitate directly out of solution onto the seafloor. This is much more common in groundwater environments such as caves, but it apparently can happen in the ocean, too.
The composition of limestone layers ranges from almost exlusively type 1 to almost exclusively type 3. It is part of the reason why limestone building materials are available in such a wide variety of colors, textures and hardnesses. The range of temperatures and pressures and time a layer has been subjected to also have a considerable influence. Limestone under great pressure that is heated beyond a certain point becomes marble, which almost always erases all fossil evidence.
This thread is attempting to address the issue of how a flood could produce hundreds of feet of limestone layers in a single year, which at the rates we observe today would take well over a million years.
--Percy

This message is a reply to:
 Message 106 by jar, posted 03-29-2006 8:43 PM jar has not replied

Replies to this message:
 Message 111 by roxrkool, posted 03-30-2006 9:12 AM Percy has not replied

  
Percy
Member
Posts: 22392
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.3


Message 113 of 128 (299629)
03-30-2006 4:43 PM
Reply to: Message 112 by Christian
03-30-2006 4:09 PM


Re: Request that we address the topic
Christian writes:
And again I am very ignorant in this field, so perhaps I'm misunderstanding something, but doesn't Message 111indicate that there is some debate about the origen of limestone (micrite in particular)?
Debate? Between professional geologists? No, there is no debate.
The short answer is that you're being flim-flammed into thinking there's any scientific doubt on the matter. If you want a longer answer I think you should propose your own thread.
You keep alluding to your ignorance, but I don't think that's really a problem because ignorance is easily remedied. The real problem is that you don't know who to believe. Your inclination is to believe those telling you things consistent with your beliefs. You're also inclined to give credence to professional scientists.
Are you a professional or is there something you're really good at, perhaps a craft or a sport? Let me pick the medical profession, since everyone's been to the doctor. Let's say you're a doctor specializing in backs. You show a patient their X-Ray of a herniated disk with a fragment pressing dangerously against the spinal column. You tell them they're in danger of eventual paralysis without surgery. The patient isn't so sure. He's heard stories that plenty of people do fine without surgery. His chiropractor has told him that weekly manipulation is all he needs. He's read advertisements for magnets that he can wear that will fix his disk. A friend had wonderful results from sleeping next to a model pyramid. A neighbor down the street with a back problem saw a faith healer and now plays rugby. Doesn't all this imply that there is some debate about whether surgery is necessary?
The relevant question: Debate between whom? Between doctors in your profession? No, of course not. The patient is paying the most attention to the message he wants to hear, that he's not really in any danger and that he'll be alright without painful surgury.
And that's your real problem, not ignorance. Your rational side knows that the professionals who make a career in science are much more likely to be right, but they're not telling you the message you want to here. Walt Brown has made a career not out of science, but out of selling books and other materials to support a ministry, but he's got the right message as far as you're concerned.
--Percy
This message has been edited by Percy, 03-30-2006 04:44 PM

This message is a reply to:
 Message 112 by Christian, posted 03-30-2006 4:09 PM Christian has replied

Replies to this message:
 Message 114 by Minnemooseus, posted 03-30-2006 5:05 PM Percy has replied
 Message 117 by Christian, posted 03-30-2006 5:41 PM Percy has not replied

  
Percy
Member
Posts: 22392
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.3


Message 115 of 128 (299635)
03-30-2006 5:20 PM
Reply to: Message 114 by Minnemooseus
03-30-2006 5:05 PM


Re: There are always details to be debated
Moose writes:
I find it mighty surprising that you would make a statement such as the above.
Hey, I'm just full of surprises today!
Was the context more ambiguous than I thought? The point I thought I was making was the very same one you made, that "there is indeed broad agreement that the majority of limestones are of direct or indirect biological origin." Unless there are geologists out there somewhere seriously arguing for a significant non-organic origin, there's no debate about this. I didn't mean to imply there's no debate about any limestone anywhere.
--Percy

This message is a reply to:
 Message 114 by Minnemooseus, posted 03-30-2006 5:05 PM Minnemooseus has not replied

  
Percy
Member
Posts: 22392
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.3


Message 119 of 128 (299700)
03-30-2006 9:17 PM
Reply to: Message 118 by roxrkool
03-30-2006 7:03 PM


Re: One small question.
roxrkool writes:
I THINK it's saying most limestone is biogenically-derived, but I could be wrong, I had a hard time following the bio stuff.
I can't see any other possible conclusion, and he really emphasizes this point with the "probably mythical" parenthesized comment in reference to purely non-biogenic limestone.
If inorganic sedimentary limestone deposits collected in any significant amounts on sea floors in areas with no significant presence of "heterotrophic bacteria" then we would already know about it. All the articles about limestone layers say they formed in warm shallow seas not because geologists just made it up so they could go home early, but because that is where they've observed limestone layers forming today. And I assume they find that cold, deep seas produce much less in the way of limestone deposits.
The more closely you investigate anything the more you find that the picture is more complicated than you thought, but as long as the big picture is informed by the lower level detail that picture will be correct. Simplified, of course, but correct. This is the process of popularization in science. I assume the writers of the popularizations are rendering pictures consistent with lower level details. I assume if such popularizations were largely wrong that geologists would let us know about it. I assume when I read these popularizations that I'm learning a simplified view, not a wrong view that happens to be simple enough for laypeople.
You can point to a picture of a green tablecloth on a page of a magazine and say, "This is green," and then someone can put it under a microscope and say, "Aha! There are dots of red mixed in." And so there are, but that doesn't mean the tablecloth isn't green.
Christian is making the mistake of looking through the microscope before she understands the big picture, and every time the equivalent of one of those dots of red comes into view she thinks she's found something that just doesn't add up. She doesn't realize that the detailed picture is always messy and complicated and confusing. That's why you have to go to college for 8 years to even begin to understand this stuff. That's why they teach 1st grade science in 1st grade and 12th grade science in 12th grade and not the other way around.
Christian will focus her magnifying glass here and there in no particularly connected order and be given little-understood explanations and never fit it all together. And I think Walt Brown, maybe not consciously, knows that his work has this effect. He knows it isn't necessary to convince, only to confuse. I think he's pretty good at what he does.
--Percy

This message is a reply to:
 Message 118 by roxrkool, posted 03-30-2006 7:03 PM roxrkool has not replied

Replies to this message:
 Message 122 by Coragyps, posted 03-30-2006 11:01 PM Percy has replied

  
Percy
Member
Posts: 22392
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.3


Message 123 of 128 (299753)
03-31-2006 8:54 AM
Reply to: Message 122 by Coragyps
03-30-2006 11:01 PM


Re: One small question.
Coragyps writes:
Partly because, IIRC, calcium carbonate snowing down from the photosynthetic zone near-surface largely redissolves before it ever gets to a cold. deep ocean floor. Calcium carbonate is a bit odd in that respect - it's less soluble in cold water than warm. That's why it's the hot-water heater and pipes in your house that scale up if you have hard water.
Jesus Christ I'm dense! I just had a water softener installed a month ago, read all about this effect, but never put 2 and 2 together.
So let's imagine an area of very deep ocean near the equator with an abundance of water life, including algae, near the top of the water column, and with cold, dark water a couple miles below. The rain of particulate calcium carbonate skeletons from above dissolves before it reaches the sea floor. This process goes on for millenia, and one could argue that eventually the cold water at the bottom of the water column will supersaturate with dissolved calcium carbonate and that it would just precipitate out on the sea floor at a steady rate after that.
But once dissolved the calcium carbonate is much more subject to diffusion than to gravity, and so since we can assume marine geologists have in general not found significant formation of limestone layers in such regions, it must diffuse away to an extent sufficient to prevent supersaturation.
If a combination of diffusion and water currents carried such calcium carbonate rich water to shallow regions where it could warm, then the calcium carbonate would precipitate out, and this could be another factor in micrite formation.
Are we really sure that calcium carbonate is more soluble in cold water than warm? Poking about on the web definitely indicates that it is solubility that is the factor, but this makes no sense to me. I've found a couple mentions that when CO2 concentrations in water drop, which happens with higher temperature, that CaCO3 tends to precipitate out, so I don't think solubility is the whole story, but I couldn't find any details.
How does algae build its calcium carbonate shells? Does it just use calcium carbonate that's already dissolved in ocean water? Or does it create calcium carbonate? I've seen hints that they remove calcium from the water to create the shells, but no details. The world is so full of calcium carbonate that we dump it on our lawns, and there does not seem to be any large-scale inorganic source, so I expect the answer is that they create the calcium carbonate from calcium in the sea water.
--Percy

This message is a reply to:
 Message 122 by Coragyps, posted 03-30-2006 11:01 PM Coragyps has not replied

Replies to this message:
 Message 124 by roxrkool, posted 03-31-2006 9:20 AM Percy has replied
 Message 128 by PurpleYouko, posted 03-31-2006 4:35 PM Percy has not replied

  
Percy
Member
Posts: 22392
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.3


Message 125 of 128 (299776)
03-31-2006 9:37 AM
Reply to: Message 124 by roxrkool
03-31-2006 9:20 AM


Re: FYI
roxrkool writes:
Carbonate Compensation Depth.
Ah, thank you!
Isn't this sentence from the last paragraph incorrect:
In the late Eocene the development of Antarctic glaciers resulted in colder deep sea temperatures leading to a deeper CCD.
Presumably, colder deep sea temperatures would mean that CCD is shallower, not deeper. If we can get consensus about this then we should edit the entry.
--Percy

This message is a reply to:
 Message 124 by roxrkool, posted 03-31-2006 9:20 AM roxrkool has not replied

Replies to this message:
 Message 126 by Coragyps, posted 03-31-2006 10:17 AM Percy has replied

  
Percy
Member
Posts: 22392
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.3


Message 127 of 128 (299799)
03-31-2006 11:43 AM
Reply to: Message 126 by Coragyps
03-31-2006 10:17 AM


Re: FYI
Coragyps writes:
A quick Google Scholar look indicates that maybe the Wiki author is oversimplifying - carbon dioxide levels fell dramatically in the late Eocene, which both deepened the CCD and also contributed to Antartica cooling off. You are correct, though, that just colder water would mean shallower CCD.
Well, Wiki is all about getting things right. If we can develop a concensus (hopefully Edge and Rox will chime in) then we should fix it. Here's a proposal (I went for simpler instead of more complex):
In the late Eocene a decrease in carbon dioxide levels resulted in a deeper CCD.
If we decide more information is the way to go, then how about this:
In the late Eocene a decrease in carbon dioxide levels led to the development of Antarctic glaciers and colder deep sea temperatures, which by itself would have led to a shallower CCD, but the decreased carbon dioxided levels more than compensated and caused a deeper CCD.
--Percy

This message is a reply to:
 Message 126 by Coragyps, posted 03-31-2006 10:17 AM Coragyps has not replied

  
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