Scallops on cave walls.

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Postby driggs » Jun 27, 2007 10:08 pm

Caverdale wrote:I think you wrote that incorrectly and really meant the steep side is on the upstream side and faces downstream. Referring to the diagram, the steep side is directly below the circle with the "1" inside and the tail end of the arrow pointing right or downstream. I am puzzled by Sweeting's explanation which seems backwards from the rest.


I definitely didn't write that incorrectly!

I'd scan Curl's diagram if I had a scanner, but...

The vector 'd' shows the water flow direction. Upstream is to the left, downstream, where the arrow is pointing, is to the right. The scallop crest, underneath the number 1 in a circle, clearly shows the steepest angle on the right, or downstream, side.

Art Palmer's diagram is even simpler and more clear. While I'm no geologist, I just spent all of last week studying under Art at Mammoth Cave, and we spent a great deal of time examining scallops to determine paleo-flow patterns.

:beatinghorse:
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Postby driggs » Jun 27, 2007 10:40 pm

In the hopes that language is confusing the issue (facing vs. pointing, downstream vs. upstream, steep vs. gradual, etc.), I've whipped up a graphic to prove that I'm neither a geologist nor an artist. Limestone on the bottom, water on the top.

Image

Do the disagreers also disagree with this diagram?
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Postby Scott McCrea » Jun 28, 2007 6:38 am

driggs wrote:In the hopes that language is confusing the issue (facing vs. pointing, downstream vs. upstream, steep vs. gradual, etc.)

:exactly:

Do the disagreers also disagree with this diagram?

I think this diagram is correct. Whew, that was a confusing thread. :laughing:
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Postby Teresa » Jun 28, 2007 7:35 am

This explanation may be accurate for limestone scallops, but what about dolomite caves, where the dissolution process is different? Are there scallops in lava tubes?

Presumably this only applies to horizontal caves...

Nothing is as easy as it seems.
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Postby l lambert » Jun 28, 2007 7:38 am

Driggs is talking about scallops in yankee caves which happen to be bassakwards. Real cave scallops have steep side upstream! Leo
Last edited by l lambert on Jun 28, 2007 9:13 am, edited 1 time in total.
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Postby George Dasher » Jun 28, 2007 8:37 am

You have an additional problem that water can eddy and flow upstream for short distances. You can therefore have scallops that form backwards to the main water flow.

I know that there was a theory ages ago that Culverson Creek Cave priated the water from Raders Valley. There were three bits of evidence for this theory: the sharp bend in the surface Culverson Creek upstream and west of the cave, a "backwards" pointing tributary to CC in that area, and some "backwards" pointing scallops in the cave itself.

But then someone pointed out that they thought the scallops were formed in an area where the water was eddying, so the whole theory fell apart. Then (I think) they lost the location of the scallops.

But it was a pretty weak theory to begin with.
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Postby l lambert » Jun 28, 2007 9:11 am

I was standing in the entrance to Lookout Mtn. cave explaining rudimentary speleogenesis to a group of paleontologists. One of the PH D's in the group(his specialty was birds) asked if this was the outfall. I said yes this was the downstream end and therefore the outfall. He then proceeded to point out scallops that indicated flow INTO the cave. I was a bit miffed,after all his specialty was birds so what did he know about caves, but low and behold he was right. There were scallops that showed flow into the cave entrance. It took me awhile to figure this out but what happened is akin to what Mr. Dasher is talking about.
Scallops will show the direction water was flowing when carving that particular scallop. Leo
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Postby l lambert » Jun 28, 2007 9:29 am

A scallop is the 'scoop' on the wall. The peak in between is exactly that, the point between two scallops. The scallop has a steep side and a shallow side. the steep side of the scallop/bowl will be on upstream side of flow. Thought I would add this after reading more of Driggs posts. Leo
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Scallops

Postby wvdirtboy » Jun 28, 2007 5:07 pm

L Lambert wrote:He then proceeded to point out scallops that indicated flow INTO the cave. I was a bit miffed,after all his specialty was birds so what did he know about caves, but low and behold he was right. There were scallops that showed flow into the cave entrance. Leo


Lateral potholes (http://tinyurl.com/27947d) are big indentations on cave walls in which vortices (eddies) form during floods. The water flows in the downstream end turns around and flows upstream... opposite the direction of flow in the main channel. This is actually fairly common, so you want to make sure you are looking at scallops that are not in wall pockets or sheltered areas.

You can check this paper for more about that: http://www.journals.uchicago.edu/cgi-bin/resolve?id=doi:10.1086/340442
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Postby Marbry » Jun 29, 2007 1:53 am

I think Mr. Lambert hit it on the head. Most of the confusion seems to be related to where you define the break between scallops.

If it is as he said peak to peak, which is where it should be, then the steep side is on the upstream side of the scallop. If you define it as trough to trough then it is on the downstream side (although that's wrong of course ;-) ).

Actually they should probably be called flow notches or something since they are really the inverse of scallops.
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Postby Dwight Livingston » Jun 29, 2007 7:24 am

Marbry wrote:Actually they should probably be called flow notches or something since they are really the inverse of scallops.


Perhaps, though the online definition below shows that our confusion here reflects a language wide confusion.

scallop - one of a series of rounded projections (or the notches between them) formed by curves along an edge . . .
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Postby Illinois Caver » Jun 30, 2007 12:04 am

I couldn't resist in getting in on this discussion!

The scallops are good indicators of cave origin and past stream flow. I'm not sure if this was mentioned, but it also can help indicate phreatic or vadose origin.

I'm currently looking at some dolomitic (not sure if that is a word, but I coin it anyway) caves and scallops are all but missing. I think it is due more to the origin rather than the composition.

Oh, Hi David! Good to see you put that Karst Geology Course to good use! :kewl:

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Postby Teresa » Jun 30, 2007 1:58 pm

Illinois Caver wrote:I'm currently looking at some dolomitic (not sure if that is a word, but I coin it anyway) caves and scallops are all but missing. I think it is due more to the origin rather than the composition.
-Troy


Well, it's a bit difficult to sort out origin from composition. *|:-) Like yourself, I've not seen many 'classical' flutes or directional callops in dolomite caves. The walls, though, *are* scalloped, almost in an anastomosic and spongework pattern. It seems to be due to the fact that dolomite caves often leave residual dolomite sand...dissolution liberates ceiling and wall particles, but doesn't entirely dissolve the dolomite. Hence, in moving water dolomite caves the wall rock is often rough-- not nearly as polished as some limestone caves I've been in.

This is further complicated by the fact that these secondary dolomites may be only imperfectly dolomitized--some parts of the wall may still be limestone!

A good place to study this (if anyone wants to) would be the large caves in Perry County, where the caves are formed in both limestone and dolomite formations.
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Scallops, scallops everywhere...

Postby spudlunker » Jul 1, 2007 3:36 pm

:hairpull:

I've been studying scallops in gypsum caves of the Castile formation and in the interbedded dolomite/gypsum caves of the Seven Rivers, Rustler, and San Andres formations of southeastern New Mexico for some time. I'm currently finalizing a paper in which I've used scallops to determine several flow parameters in a conduit in Parks Ranch Cave. It would be interesting if those people who are engaged in this thread could get together for discussion, lunch, beer, etc. during convention. I'd love to pick the brains of others (you're welcome to pick my brain as well, but you'll need one of those teeny, tiny dental picks).

Well, any takers?

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Postby wvdirtboy » Jul 2, 2007 9:59 am

I will be at convention and would certainly like to talk about scallops and any other sculpted forms (e.g., potholes) that folks are interested in. I won't be in IN until Tuesday though.
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