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Author Topic:   Geologic Column
Minnemooseus
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Posts: 3881
From: Duluth, Minnesota, U.S. (West end of Lake Superior)
Joined: 11-11-2001
Member Rating: 4.0


Message 2 of 55 (50721)
08-16-2003 3:35 PM


I happened to rediscover this topic. Right now, I don't have time to pursue it further, but I thought I'd give it a bump.

quote:
Links:
http://earthsci.org/teacher/basicgeol/geotim/geotim.html
http://www.geol.umd.edu/~tholtz/G104/104Y2K/104Lec04.htm

The above are both nice introductions to geologic study methodology etc.

Perhaps Edge would be up to the task of re-outlining the difference between the textbook version of the geologic column, and the real world version of the geologic column. I know we've had some discussion of this in the past. In short, the textbook version is a timeline, which really says nothing about rocks. This is why there is a lot of truth to the statement "The geologic column only exists in textbooks".

Gotta go,
Moose


Replies to this message:
 Message 3 by edge, posted 08-16-2003 4:16 PM Minnemooseus has replied

  
Minnemooseus
Member
Posts: 3881
From: Duluth, Minnesota, U.S. (West end of Lake Superior)
Joined: 11-11-2001
Member Rating: 4.0


(1)
Message 50 of 55 (832808)
05-11-2018 1:11 AM
Reply to: Message 3 by edge
08-16-2003 4:16 PM


Replay of entire message 3 (+ comments)
...perhaps a quick treatment...

quote:
Perhaps Edge would be up to the task of re-outlining the difference between the textbook version of the geologic column,...

Actually, I have a text in front of me that shows 15 different geological columns for the Cambrian alone... I think what you mean here is the 'geological column as most YECs see it'. This is actually the Geological Time Scale as your first site points out quite well. There is basically one time scale. How it got filled with rocks is a different story. Every location on earth has its own geological column.

quote:
... and the real world version of the geologic column.

Yes, this (these) are the real story. They represent the actual rocks occurring at a given location, in order of occurrence. They essentially fill in the time scale 'trays' with rocks. In most cases, not all periods of the time scale are represented. This is not unexpected or a violation of some geological precept.

In fact, we expect gaps, some of them quite large. This is because of erosion or non-deposition of rocks in those gaps which we generalize as 'unconformities'. We know unconformities are real, because we live on one. There have been no significant sedimentary rocks deposited on the Canadian shield (for instance) for as long as anyone can remember.

quote:
I know we've had some discussion of this in the past. In short, the textbook version is a timeline, which really says nothing about rocks. This is why there is a lot of truth to the statement "The geologic column only exists in textbooks".

IF one equates the geological column with geological time scale, yes. However, that is only done by YECs as far as I know.

New comments:

Repeating the tail end of the above quoted (quote box format changed):

Edge writes:

Minnemooseus writes:

I know we've had some discussion of this in the past. In short, the textbook version is a timeline, which really says nothing about rocks. This is why there is a lot of truth to the statement "The geologic column only exists in textbooks".

IF one equates the geological column with geological time scale, yes. However, that is only done by YECs as far as I know.

There are as many geologic columns (stratagraphic columns) as there are points on the Earth. Such are essentially one specific locations fragment of a larger geologic cross section.

Now there are such things as generalized geologic columns, where the characteristics of a larger geologic cross section or even an area are condensed down to a "cartoon" column. Such illustrate relationships of the areas geology but should not be literally interpreted as being truly real.

When geologists are talking about a geologic column, one must consider the context of the discussion. They might be talking about the stratigraphy of a specific location. BUT if it is a broad discussion of THE GEOLOGIC COLUMN, geologic column is (probably) being used as an alternative phrasing for THE GEOLOGIC TIME SCALE.

Here in northern Minnesota, a group of geologists may talk of going out and looking at the preCambrian. That does not mean they are planning on doing some time travel. It means that they are going to be looking at some rocks of preCambrian age.

Moose


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