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Author Topic:   How do geologist know what they are looking at really is what they say it is?
jar
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From: Texas!!
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Message 76 of 88 (790913)
09-07-2016 8:32 PM
Reply to: Message 75 by dwise1
09-07-2016 8:12 PM


Re: a short side trip to satisfy my curiosity.
So there really are specific indicators that will show when a portion of a geological column has been disturbed, even turned upside down.

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Dr Adequate
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Message 77 of 88 (790925)
09-08-2016 1:48 AM
Reply to: Message 76 by jar
09-07-2016 8:32 PM


Re: a short side trip to satisfy my curiosity.
Oh yes. I wrote this article. Also if the bit that's been overturned is big enough you could use dating methods. Or, as in the photograph, the folds may still be visible.
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Pressie
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From: Pretoria, SA
Joined: 06-18-2010
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(1)
Message 78 of 88 (790932)
09-08-2016 7:06 AM
Reply to: Message 71 by jar
09-07-2016 8:24 AM


Re: Spy vs Spy
jar writes:

... which products or product would get produced in each situation; or. are you saying the the characteristics of bituminous coal (as one example) is different in the situations you mention. Is it a matter of specific chemical composition varying by source material?

Not really. Yes and no. It's complicated. You have to realise the official global classification system is based on northern hemisphere coals. A, B, C, etc. and how they behave when burnt in power stations. In Europe and America power plants are built around that northern hemisphere coal classification system.

Southern hemisphere coals have different properties. What is classified as a bitumionous coal in the northern hemisphere has similar properties to a sub-bituminous coal in the southern hemisphere (and India). It's not a matter of specific properties, it's basically (more or-less) based on how the coals 'behave' in power stations.

So, it's not an easy answer.

In Europe and Russia and the US, local coals classified as bituminousus are the best to provide the most efficient power in those power stations. In Africa and Australia and South America and India the coals classified as sub-bituminous are the most efficient. One of the reasons is that northern hemisphere coals were formed from different plant material from a slightly different period than those formed in what is now Southern hemisphere coal.

So, it's not an easy answer!

Edited by Pressie, : No reason given.


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jar
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Posts: 29149
From: Texas!!
Joined: 04-20-2004
Member Rating: 2.8


Message 79 of 88 (790938)
09-08-2016 8:40 AM
Reply to: Message 78 by Pressie
09-08-2016 7:06 AM


Re: Spy vs Spy
still a few questions.

In your explanations there are just so many things still open.

Pressie writes:

In Europe and Russia and the US, local coals classified as bituminousus are the best to provide the most efficient power in those power stations. In Africa and Australia and South America and India the coals classified as sub-bituminous are the most efficient.

That begs the question "What is different, the classification system, the actual coal, the power plants, all three?"


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Pressie
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Message 80 of 88 (790939)
09-08-2016 9:05 AM
Reply to: Message 79 by jar
09-08-2016 8:40 AM


Re: Spy vs Spy
Actually, all of them.

But, you have to realise that the classification systems in the northern hemisphere work for most northern hemisphere coals (and some southern hemisphere coals). In the southern hemisphere coals the official classification system more-or-less works for a lot of southern hemisphere coals (not all of them, though). Nothing ever is either black or white, lots of processes involved inbetween.

What is very obvious for all those economically exploitable coals, though, is that all those coals were formed by different natural processes over lots of time. Not one method. Lots of different methods.

The present is the key to the past.

Edited by Pressie, : No reason given.

Edited by Pressie, : No reason given.


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jar
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Posts: 29149
From: Texas!!
Joined: 04-20-2004
Member Rating: 2.8


Message 81 of 88 (790942)
09-08-2016 9:27 AM
Reply to: Message 80 by Pressie
09-08-2016 9:05 AM


Re: Spy vs Spy
Pressie writes:

What is very obvious for all those economically exploitable coals, though, is that all those coals were formed by different natural processes over lots of time. Not one method. Lots of different methods.

The present is the key to the past.

Okay, next step.

You added another qualifier, "economically exploitable", and while I realize that has significance when it comes to commercial applications, we are hopefully just dealing with the actual geology in this thread. I also understand that most of the data available will come from those sites that were economically exploitable and that is expected but there is also likely an similar body of data on sites where it was not economically exploitable.

Let's step away from the economic considerations.

The general designations of coal were listed as peat to lignite, to bituminous to anthracite and eventually to graphite.

Can you give us a short physical description of how someone identifies each of those in the field?


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Pressie
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Posts: 1696
From: Pretoria, SA
Joined: 06-18-2010
Member Rating: 2.9


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Message 82 of 88 (790999)
09-09-2016 6:27 AM
Reply to: Message 81 by jar
09-08-2016 9:27 AM


Re: Spy vs Spy
It's all subjective in the field. It comes from experience and a hand held magnifiers.

Peat basically is derived from plant material still recognisable as plant material by the open eye.

Lignite is usually brown coal that can be seen by the naked eye as originating from plant material.

Sub-bituminous coals are black with a dull luster.

Bituminous coals are black with a bright luster.

Anthacites are black and have a very bright luster and have a lower relative density than bituminous coals.

Graphites are black with a dull luster and crumbling like a clot of damp sand.

These are general rules and don't always apply everywhere. Most Gondwana coals have bands of bright and dull coal. As always it's not always either black or white, but somewhere in between.

Edited by Pressie, : No reason given.

Edited by Pressie, : No reason given.

Edited by Pressie, : No reason given.


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edge
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Posts: 3904
From: Colorado, USA
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Member Rating: 4.3


Message 83 of 88 (791670)
09-19-2016 7:04 PM
Reply to: Message 82 by Pressie
09-09-2016 6:27 AM


Re: Spy vs Spy
It's all subjective in the field. It comes from experience and a hand held magnifiers.

Ya got that right!

Some things don't change, no matter which hemisphere.


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Pressie
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Posts: 1696
From: Pretoria, SA
Joined: 06-18-2010
Member Rating: 2.9


(2)
Message 84 of 88 (791703)
09-20-2016 5:59 AM
Reply to: Message 83 by edge
09-19-2016 7:04 PM


Re: Spy vs Spy
Yes, -"The best geologist is he who has seen the most rocks."- Herbert Harold Read

Edited by Pressie, : No reason given.


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jar
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Posts: 29149
From: Texas!!
Joined: 04-20-2004
Member Rating: 2.8


Message 85 of 88 (796333)
12-28-2016 8:54 PM


So what is in this picture?
Take a look at this picture:

In this is see lots of layered slabs and on one slab in the upper right area what looks a lot like a dried mud surface, but there is also lots of indications of weathering, the lower bald spots that look like loose soil or dirt.

What can be said about how the stuff in this picture was created?


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Coyote
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Message 86 of 88 (796335)
12-28-2016 9:00 PM
Reply to: Message 85 by jar
12-28-2016 8:54 PM


Re: So what is in this picture?
I'd want a little context. Otherwise, that looks like Mars...

Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.

Belief gets in the way of learning--Robert A. Heinlein

In the name of diversity, college student demands to be kept in ignorance of the culture that made diversity a value--StultisTheFool

It's not what we don't know that hurts, it's what we know that ain't so--Will Rogers

If I am entitled to something, someone else is obliged to pay--Jerry Pournelle

If a religion's teachings are true, then it should have nothing to fear from science...--dwise1

"Multiculturalism" demands that the US be tolerant of everything except its own past, culture, traditions, and identity.


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jar
Member
Posts: 29149
From: Texas!!
Joined: 04-20-2004
Member Rating: 2.8


Message 87 of 88 (796343)
12-28-2016 10:13 PM
Reply to: Message 86 by Coyote
12-28-2016 9:00 PM


Re: So what is in this picture?
It is mars but that is partly why I am asking the question.

The topic is "How do geologist know what they are looking at really is what they say it is?" and here is such an example.

What I see was described above but we have real geologists here that I hoped could perhaps expand on what is seen in the image.


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edge
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Posts: 3904
From: Colorado, USA
Joined: 01-09-2002
Member Rating: 4.3


Message 88 of 88 (796400)
12-29-2016 2:38 PM
Reply to: Message 85 by jar
12-28-2016 8:54 PM


Re: So what is in this picture?
What can be said about how the stuff in this picture was created?

Having been fooled by nature too many times to count, I'd say, not a whole lot. Certainly these are boulders of thinly bedded material, partially covered by transported (see the small ripples) sand(?), of a different composition. Possibly mud cracks are present, but without direct observation it could be some other things. The best possibility is water lain, fine sand and silt or some kind of eolian deposit (possible large-scale cross-beds on the left side of image). But that's pretty uncertain.

To me, all of the Mars pictures are 'flat', without a lot of definition. I'd like to see colors, too.


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