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Rosetta Stones

Rosetta Stones

Adventures in the good science of rock-breaking.

Angular Unconformkitty

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(I figured I'd do a repost by way of introducing you to Geokittehs. Evelyn Mervine and I - okay, mostly Evelyn - have discovered cats make excellent geological models. It's amazing how much you can learn by correlating cats with science. I'm sure this can be done with just about any animal. Dog lovers are welcome to start their own blogs, partisans of other cute creatures should feel free to join the fray, and then we can do mock battle. Let the intertoobz explode with geological animals of all species. Someday, I want someone to walk up to us and say, "I had absolutely no interest in science until I saw Geokittehs!" Or Geogoggies, or Geootters, or whatever else we manage to come up with. There are many paths to science. No reason some of them can't be adorable.)

Brian Switek's lovely Margarita takes us back to the origins of modern geology:

Angular Unconformkitty

We have three features here. Long, long ago, the vertical bits at the bottom would have been horizontal, nice sedentary sediments laid down in possibly peaceful waters. Obviously, something rather dramatic happened after they lithified, and they got pushed from horizontal to vertical - much like what happens to me when the alarm goes off in the morning. Time and possibly tide wore away whatever ended up atop the formerly-horizontal vertical bits. Then, another peaceful sea laid down a nice horizontal layer of delight. We can see some minor deformation, some of which may represent soft sediment deformation and some, especially at the left, seeming to represent presently-active tectonic forces rotating some of the horizontal stuff into a different orientation. And to the right, we seem to have a nice example of a mafic dike intruding both layers, which would tell us both sets of sediments were laid down before magma intruded. It's an angular unconformkitty James Hutton would have been proud of!

For sake of comparison, I shall now present Hutton's famous angular unconformities.

Hutton's Unconformity at Jedburgh, Scotland, illustrated by John Clerk in 1787 and photographed in 2003. Image courtesy Wikimedia Commons

And my favorite, Siccar Point:

Hutton's angular unconformity at Siccar Point where 345 million year old Devonian Old Red Sandstone overlies 425 million year old Silurian greywacke. Image courtesy Wikimedia Commons.

Of course, I can't let a mention of Siccar Point go by without linking Chris Rowan's lovely post about it. Enjoy!

The views expressed are those of the author and are not necessarily those of Scientific American.

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