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Author Topic:   Introduction To Geology
Pressie
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Posts: 2074
From: Pretoria, SA
Joined: 06-18-2010
Member Rating: 2.7


Message 34 of 293 (635142)
09-27-2011 7:05 AM
Reply to: Message 33 by edge
09-26-2011 9:08 PM


Re: Minerals and rocks: definitions
Hi guys

This is making a very difficult thread a lot more difficult.

I think we should provide the "official" geological explanations of the words crystal and mineral.

Crystal: A homogenous, solid body of chemical element, compound, or isomorphous mixture, having a regularly repeating atomic arrangement that may be outwardly expressed by plane phases.

Isomorphous mixture: Two or more crystalline substances to have similar chemical composition, axial ratios, and crystal forms, and to crystallize in the same crystal class. Such substances form an isomorphous series.

Mineral: (a) a naturally occurring inorganic element or compound having an orderly internal structure and characteristic chemical composition, crystal form, and physical properties. Those who include the requirement of crystalline form in the definition would consider an amorphous compound such as opal to be a mineraloid.
(b) Any naturally formed inorganic material, i.e. member of the mineral kingdom as opposed to the plant and animal kingdoms.

From Bates, R.L. and Jackson, J.A. (Editors), 1980. Glossary of Geology, Second Edition. American Geological Institute. Falls Church, Virginia.

This makes organic material such as amber a mineraloid, not a mineral. Any organic material, such as coal, therefore is not a mineral (although used as such colloquially).

Dr Adequate has a very difficult time at hand for a basic course in geology. Let’s not make it more difficult for him!


This message is a reply to:
 Message 33 by edge, posted 09-26-2011 9:08 PM edge has not yet responded

    
Pressie
Member
Posts: 2074
From: Pretoria, SA
Joined: 06-18-2010
Member Rating: 2.7


Message 39 of 293 (636901)
10-12-2011 12:33 AM
Reply to: Message 38 by Robert Byers
10-11-2011 2:32 AM


Robert Byers writes:

AMEN.
Geology is about history.

No, geology is the study the earth. The study of rocks is a very important part when studying the earth.
Robert Byers writes:

...it is only the processes that matter.....

No, it's those rocks that matter. That's it.
Robert Byers writes:

... as the intimate particles of these rocks....

I've seen people being "intimate", even done it myself a few times (not enough to my liking). Never seen rock particles being "intimate".
Robert Byers writes:

... did not form themselves together as a independent thought.

Rocks don't think. They exist as rocks.
Robert Byers writes:

... Only the processes matter in geology.

No, only the rocks matter. That's what we study.
Robert Byers writes:

The rocks are defined by their history.

No, they're not. They are defined by their composition.
Robert Byers writes:

Creationists have to insist that geology is from historic actions and so investigation must be about history.

Well, it's been long established that creationists don't do science. They pretend that they do, but geologists are not as stupid creationists think they are. Geologists work on empirical, verifiable evidence. Creationist work on belief. Big difference.
Robert Byers writes:

We see a difference between science class and history class.

Geology is a natural science. History is not. Big difference between the two.

Edited by Pressie, : No reason given.


This message is a reply to:
 Message 38 by Robert Byers, posted 10-11-2011 2:32 AM Robert Byers has responded

Replies to this message:
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Pressie
Member
Posts: 2074
From: Pretoria, SA
Joined: 06-18-2010
Member Rating: 2.7


Message 42 of 293 (637184)
10-14-2011 1:37 AM
Reply to: Message 40 by Dr Adequate
10-12-2011 5:42 AM


Sorry about over-reacting to Robert. I tend to overreact to novices who think they know everything and also think that all those hundreds and thousands of real geologists all are wrong. To me this is a sign of complete delusion and it would be safer for humanity if such a person is treated at some mental institution. Still too many sky-scrapers and planes around to feel safe with so many deluded people walking the streets.

I disagree with you. The rocks are and were studied. The processes forming rocks are and were also studied. After that the processes by which the rocks under investigation were formed can be deducted as we can study the processes by which such rocks are formed today.

Those different rocks are and were classified after studying them. The study of rocks lead to classifications such as Igneous, Sedimentary and Metamorphic. We can study those rocks very systematically.

For example: After studying the Clarens formation of the Karoo Sequence, it has been found that said formation has all the characteristics of Aeolian deposits, therefore it was deposited by the working of wind. That’s geology.

As far as the oil deposits go, no magic. The Mississippi Delta exists. To simplify: to find oil we start looking for similar environments.

Edited by Pressie, : No reason given.


This message is a reply to:
 Message 40 by Dr Adequate, posted 10-12-2011 5:42 AM Dr Adequate has responded

Replies to this message:
 Message 43 by Dr Adequate, posted 10-14-2011 1:59 AM Pressie has responded

    
Pressie
Member
Posts: 2074
From: Pretoria, SA
Joined: 06-18-2010
Member Rating: 2.7


Message 46 of 293 (637294)
10-14-2011 3:13 PM
Reply to: Message 45 by Jazzns
10-14-2011 10:59 AM


Re: Igneous Rocks
I think that the word "basoliths" was a spelling mistake. I missed it, too.
From http://en.wikipedia.org/wiki/Batholith
A batholith (from Greek bathos, depth + lithos, rock) is a large emplacement of igneous intrusive (also called plutonic) rock that forms from cooled magma deep in the Earth's crust. Batholiths are almost always made mostly of felsic or intermediate rock-types, such as granite, quartz monzonite, or diorite (see also granite dome).
Plutons include batholiths, dykes, sills, etc. Batholiths are felsic, not mafic. Not all plutons have these characteristics. From http://www.geolsoc.org.uk/...824DBE5109DD29090C9CE8ECC5EDB16
A “pluton” is any large igneous body that has congealed from magma underground. There are many sorts of pluton – including the lens-like and subhorizontal laccoliths and lopoliths, and the vertical or near-vertical sided stocks and batholiths. All these categories of pluton are defined on their overall apparent shape and relationship to the country rock. A batholith is the largest of the pluton types and by definition cover at least 100 square kilometres. A stock is a small discordant pluton, shaped like a batholith but falling below the necessary 100 square km in extent.

Edited by Pressie, : Added source of batholiths


This message is a reply to:
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Pressie
Member
Posts: 2074
From: Pretoria, SA
Joined: 06-18-2010
Member Rating: 2.7


Message 47 of 293 (637301)
10-14-2011 4:10 PM
Reply to: Message 43 by Dr Adequate
10-14-2011 1:59 AM


Dr Adequate, we don’t really disagree.
Dr Adequate writes:

But the former statement is more interesting if we use it to infer that we're looking at what used to be a desert --- a notion which has predictive and explanatory power.

We don’t even have to infer. We can see them forming today. Same characteristics.
Dr Adequate writes:

This is what distinguishes geology from stamp-collecting.

Geology follows the scientific method. Stamp collecting follows what looks good for making money. If I wanted to make money, I would actually write a statement claiming: “Geologist thinks Clarens Formation was deposited in flood!” That would be the headline in every religious tract and website in the world for years to come, notwithstanding that none of them would even know what the Clarens Formation looks like. I would appear in every AIG and CMI “publication” and website and they would would pay a lot of money for that. I, however, wouldn’t be able to live with my conscience after doing that.
Dr Adequate writes:

OK, but how do you do that? For example, suppose I find aeolian sandstone (which is a deduction about its history) over here, and I find deep marine sediment (which is a deduction about its history) over there, and if I find that they are the same age (obviously a historical judgement)…

No, it is certainly not historical. We can see it happening today. Look for the same characteristics..voila. We know exactly what happened for those rocks to be deposited.
Dr Adequate writes:

….then I can infer a coastline somewhere between the two, and then I can start looking for nearshore deposits (another historical judgement)….

Well, you won’t infer that those rocks were poofed into existence.
Dr Adequate writes:

…somewhere in the line between them, and if I find, for example, interference ripples, I would infer that they were formed by the tide and know that I was getting close to the sort of structures I'm actually looking for.

That’s because we can see interference ripples being formed today. We know what they look like.
Dr Adequate writes:

Now one could express how to do this and similar things in terms of a mechanical procedure that just involves looking at rocks and making certain measurements of isotope ratios, but only by expunging any clue as to how it actually works

We’ve got examples of exactly how it works in real life.
This message is a reply to:
 Message 43 by Dr Adequate, posted 10-14-2011 1:59 AM Dr Adequate has responded

Replies to this message:
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Pressie
Member
Posts: 2074
From: Pretoria, SA
Joined: 06-18-2010
Member Rating: 2.7


Message 58 of 293 (641726)
11-22-2011 1:49 AM
Reply to: Message 57 by Dr Adequate
11-21-2011 12:04 PM


Re: Chemical Weathering
Dr Adequate,

This is a very difficult subject, but you summerized it very well.

Of course there are so many chemical reactions happening in "rocks" coming into contact with phenomena like acids, other "rocks", fluids, heat, pressure, etc. , that it is impossible to summarize them all in one post. The lesson to learn, I think, is that chemical weathering happens according to chemistry. We can study the "rocks" and the chemical reactions they part take in and we can study the products of said chemical reactions.

Thank you.


This message is a reply to:
 Message 57 by Dr Adequate, posted 11-21-2011 12:04 PM Dr Adequate has responded

Replies to this message:
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Pressie
Member
Posts: 2074
From: Pretoria, SA
Joined: 06-18-2010
Member Rating: 2.7


Message 64 of 293 (643111)
12-05-2011 3:54 AM
Reply to: Message 63 by Dr Adequate
12-05-2011 12:00 AM


Re: Glaciers
Dr Adequate writes:

We can use geological dating methods, of which more will be said in later articles, to establish the times at which sheet glaciers covered northern North America and Eurasia.


Thanks for your article Dr Adequate. It really is appreciated.

A very large percentage of contributers to this forum are from North America (with a minority from Eurasia). Most of them don't realize we get similar conclusions on other continents and islands. What they don't realize is that the rocks on those continents and islands are studied, too.

Africa, South America, Australia, Antartica, Indonesia, etc., observe similar phenonema, as well. (In India they get the same results as in the South Eastern parts of Africa, Western Australia and parts of Antarica when considering the occurrence of ice-sheets).


This message is a reply to:
 Message 63 by Dr Adequate, posted 12-05-2011 12:00 AM Dr Adequate has responded

Replies to this message:
 Message 65 by Dr Adequate, posted 12-05-2011 4:39 AM Pressie has responded

    
Pressie
Member
Posts: 2074
From: Pretoria, SA
Joined: 06-18-2010
Member Rating: 2.7


Message 66 of 293 (643116)
12-05-2011 6:09 AM
Reply to: Message 65 by Dr Adequate
12-05-2011 4:39 AM


Re: Glaciers
We actually do have evidence for the last ice age (when the ice sheets covered most of North America and Eurasia), a few thousand years ago. Them rocks have no reason to tell porkies.

Edited by Pressie, : Couldn't say "***", replaced it with "tell porkies".


This message is a reply to:
 Message 65 by Dr Adequate, posted 12-05-2011 4:39 AM Dr Adequate has responded

Replies to this message:
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Pressie
Member
Posts: 2074
From: Pretoria, SA
Joined: 06-18-2010
Member Rating: 2.7


Message 68 of 293 (643161)
12-05-2011 12:40 PM
Reply to: Message 67 by Dr Adequate
12-05-2011 9:28 AM


Re: Glaciers
That's fine Dr Adequate, I concede that you are right.

We do have other geological evidence for the last ice age.

Edited by Pressie, : Added a sentence


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 Message 67 by Dr Adequate, posted 12-05-2011 9:28 AM Dr Adequate has not yet responded

    
Pressie
Member
Posts: 2074
From: Pretoria, SA
Joined: 06-18-2010
Member Rating: 2.7


Message 93 of 293 (658445)
04-05-2012 12:52 AM
Reply to: Message 91 by Artemis Entreri
04-04-2012 3:58 PM


Re:
Hi Artemis Entreri

I agree with you on the work done by Dr Adequate. This thread is excellent.

You could of course start reading on sand dunes on http://en.wikipedia.org/wiki/Dune. Don't forget the references at the bottom.

You little creationist you: "assumption" and "Uniformitarianism".

Edited by Pressie, : Changed whole answer

Edited by Pressie, : No reason given.


This message is a reply to:
 Message 91 by Artemis Entreri, posted 04-04-2012 3:58 PM Artemis Entreri has responded

Replies to this message:
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Pressie
Member
Posts: 2074
From: Pretoria, SA
Joined: 06-18-2010
Member Rating: 2.7


Message 104 of 293 (658820)
04-10-2012 12:52 AM
Reply to: Message 95 by Artemis Entreri
04-05-2012 9:26 AM


Re:
Artemis Entreti

My sentence: You little creationist you: "assumption" and "Uniformitarianism", was written with a big grinning face at the end. I was joking.

Edited by Pressie, : No reason given.


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Pressie
Member
Posts: 2074
From: Pretoria, SA
Joined: 06-18-2010
Member Rating: 2.7


Message 179 of 293 (675291)
10-10-2012 12:40 AM
Reply to: Message 177 by petrophysics1
10-09-2012 6:05 PM


Re: Petrophysics
quote:
Paraconformity= "A term introduced by Dunbar & Rodgers(1957, p.119)* for an obscure or uncertain uncomformity in which no erosion surface is discernable or in which the contact is a simple bedding plane, and in which the beds above and below are parallel"(Glossary of Geology 4th ed, p.464, Julia A. Jackson).

In your example above you have a break in the fauna. Now I don't consider that to be either "obscure" or "uncertain", so it doesn't match the definition. I'd call it an unconformity.


No, you have to realise that Dr Adequate tried to clearly explain to the readers what a paraconformity is, he used an extreme example, but gets the message across to as many readers as possible.

quote:
HOWEVER, do you FEEL it's obscure or do you FEEL uncertain about it? If you do and also think that the geologists feelings have a place in geologic descriptions by all means call it a paraconformity.
I completely disagree with this. It's not a "feeling" at all. It's following the evidence.

As a person who does a lot of core-logging, I often get contacts where the unconformity surface resembles a simple bedding plane; the strata are parallel, their's no apparant erosion, etc.

I call it a paraconformity in my logs, although I'm unsure of whether it really is one. That core has a very, very small diameter of just a few millimeters, remember, but I follow the evidence....


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 Message 177 by petrophysics1, posted 10-09-2012 6:05 PM petrophysics1 has not yet responded

Replies to this message:
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Pressie
Member
Posts: 2074
From: Pretoria, SA
Joined: 06-18-2010
Member Rating: 2.7


Message 181 of 293 (675390)
10-11-2012 12:03 AM
Reply to: Message 180 by roxrkool
10-10-2012 8:58 PM


Re: Petrophysics
Yes, absolutely, but it still is not just a feeling. It's an educated guess, backed by experience, too. And following the evidence. Not just any old feeling would do. We could call that a 'feeling' if you want too. But it's a very loose definition of the word 'feeling' then.

It's only after you've got enough evidence (well, you feel that you have enough evidence), to be able to relatively accurately model (another feeling) the deposit, where you can try and figure out where you made some wrong decisions. Even after that, you're still not 100% sure.

Don't even get me started on those Engineers. For them everything is either black or white; no grey areas inbetween. We drive them crazy and they drive us crazy.

Edited by Pressie, : Changed last paragraph as it didn't come across as intended

Edited by Pressie, : Changed spelling

Edited by Pressie, : Spelling and first paragraph


This message is a reply to:
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