M.Chapman

Scratch lines on rock surface - Geology ID

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I took this photo of some scratch marks on some rock on Skye. This is a closeup.

 

closeup-of-multi-directional-glacial-scouring-on-mudstone-rock-shown-in-foreground-of-alamy-image-mwgbw2-glen-scaladal-bay-isle-of-skye-scotland-uk-MWGBW0.jpg

 

This is a more general view showing a similar scratched rock in the foreground.

 

rocky-glen-scaladal-bay-beach-cladach-a-ghlinne-near-elgol-with-loch-scavaig-and-black-cuillin-mountains-on-the-isle-of-skye-scotland-uk-MWGBW2.jpg

 

I suspect these scratches were caused by glacial action and have captioned an keyworded accordingly. But I would value a second opinion. I think it's quite unusual to see glacial scouring scratches in several directions. I suspect this rock (boulder) was originally inverted and being pushed along a rocky surface by a glacier above. The boulder may have rotated at some point causing the direction of scratches to change. That's my theory anyway...

 

Thanks in advance

 

Mark

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Have you got 'Striations'?

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I think the first pic is a stone-age carving of an electricity pylon.

 

Alan

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9 hours ago, geogphotos said:

Have you got 'Striations'?

 

No I hadn't, thanks for that :)

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16 hours ago, geogphotos said:

Have you got 'Striations'?

 

If you have, I believe you can get pills to help.............

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Is it fossilised foliage embedded on the surface perhaps?

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1 hour ago, Brian Vickers said:

Is it fossilised foliage embedded on the surface perhaps?

No. Fossilised leaves look like, well, leaves.

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And on the far left of the first picture there's clearly a carving of a monkey wearing sunglasses.

 

Quick, sell the pic to Erich von Däniken.

 

Alan

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Personally, I think these scratches look man-made. 

I took some pics of striated rocks next to a glacier in South America a while ago and the rocks were all striated in the same direction and very smooth.

 

striated-rocks-on-the-viedma-glacier-sou

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Posted (edited)
18 minutes ago, vpics said:

Personally, I think these scratches look man-made. 

I took some pics of striated rocks next to a glacier in South America a while ago and the rocks were all striated in the same direction and very smooth.

 

striated-rocks-on-the-viedma-glacier-sou

 

I think that striations can go in two (or more) directions -- i.e. they can show two different periods of glaciation. But I'm no geologist. The scratches could also have been made by some sort of digging machine. They do look pretty rough.

 

Erich von Däniken? I thought the aliens must have got him, or perhaps he's working in the White House now. B)

Edited by John Mitchell

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55 minutes ago, vpics said:

Personally, I think these scratches look man-made. 

I took some pics of striated rocks next to a glacier in South America a while ago and the rocks were all striated in the same direction and very smooth.

 

striated-rocks-on-the-viedma-glacier-sou

I tend to agree the boulder has far to many raised sharp edges, a glacier would have ground it flat and a lot smoother, (saw a lot of those in a past life falling out of glaciers in the Falklands.)

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Posted (edited)
1 hour ago, John Mitchell said:

 

The scratches could also have been made by some sort of digging machine. They do look pretty rough.

 

This is a remote location on a Scottish Island so a digging machine is very, very unlikely.

Edited by M.Chapman

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1 hour ago, vpics said:

Personally, I think these scratches look man-made. 

I took some pics of striated rocks next to a glacier in South America a while ago and the rocks were all striated in the same direction and very smooth.

 

striated-rocks-on-the-viedma-glacier-sou

 

Yes most of the glacial scouring I've seen has created smoother rocks with all the scratch marks in the same direction. But this is often on harder rock. I believe this rock is softer mudstone. The scratches are not man-made - the location is remote and the scale too large (parallel scratches extending over a metre or so) for simple hand tool scratches. There are also numerous rocks here with similar scratch marks. The heavily glaciated (during the ice age) Cuillin mountain range is nearby where other rocks show the more conventional uni-directional scouring. 

 

It's why I photographed them, they look quite unusual.

 

Mark

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Posted (edited)

Ah-ha, I think I've found what they might be -  "drift ice abrasion marks" See article and photos here

 

PS. If the link doesn't work for you, try a different browser. It displays OK for me in Safari, but not Chrome.

 

Mark

Edited by M.Chapman

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1 hour ago, M.Chapman said:

 

This is a remote location on a Scottish Island so a digging machine is very, very unlikely.

 

Don't you remember this old joke?

 

Q: How was the Grand Canyon formed?
A: A Scotsman accidentally dropped a penny down a gopher hole.
 

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On 20/06/2018 at 20:14, M.Chapman said:

Ah-ha, I think I've found what they might be -  "drift ice abrasion marks" See article and photos here

 

PS. If the link doesn't work for you, try a different browser. It displays OK for me in Safari, but not Chrome.

 

Mark

I think you are probably right Mark. I am not an expert on glacial features but the explanation in that paper seems very plausible.

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7 hours ago, MDM said:

I think you are probably right Mark. I am not an expert on glacial features but the explanation in that paper seems very plausible.

 

Thanks. 

 

Mark

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