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24 January 2011

East wall of Baker’s Quarry

Callan showcases his contribution to this month’s Accretionary Wedge blog carnival. The theme of the Wedge is “Bake Sale,” and Callan shows a cake he “discovered,” describing its geologic origin in detail. This would be tongue in cheek, except that his mouth is already full of dessert.


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22 January 2011

Let’s coin a name for this phenomenon

I didn’t mention it yesterday, but there was one other structure that I saw at my newest outcrop on New 55. This is it: That’s a bunch of fractures. The broken rock is being altered by preferential fluid flow through the fractures. The fluid is not inert; it’s chemically active, and reacting with the rock. These reactions produce the color and weathering differences that you note in the previous images. …


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21 January 2011

Friday fold: scenes from new 55

This week’s edition of the “Friday fold” takes us to Route 55 in West Virginia, to deformed Appalachian strata of the Valley and Ridge province. A few bonus structures are also shown — some ripple marks, slickensides, and pencil cleavage.


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20 January 2011

A warm, glowing feeling

Just got this in an email: “Hi professor Bentley, This is [redacted], I had you for Geology last Spring. I just wanted to email you to first off, thank you, and second off, to ask some questions. Before I took your class Science was my worst subject , and I did everything to avoid taking it. I ended up needing it so I chose Geology since i was very slightly …


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Reminder: AW#30, the Bake Sale

This is a friendly reminder that you have one more week to prepare your brownies, cakes, puddings, eclairs, gumballs, gobstoppers, and cookies for the Accretionary Wedge Bake Sale. The deadline for the submission of entries is a week from tomorrow, next Friday, January 28. Leave a link in the comments here, or at the original post. As an example of a coincidence that reinforces the “Bake Sale” theme, here’s an …


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19 January 2011

Video book review III: evolution

Amazon links to the five books mentioned: Your Inner Fish by Neil Shubin Why Evolution is True by Jerry Coyne (and here’s his blog) The Greatest Show on Earth by Richard Dawkins (and we gave a shout out to the superb The Ancestor’s Tale by Richard Dawkins, also) (the video with the giraffe neck dissection) Evolution: the Story of Life on Earth by Jay Hosler, Kevin Cannon, and Zander Cannon …


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17 January 2011

Book review video 2

Books mentioned: Bones, Rocks, and Stars: the Science of When Things Happened, by Chris Turney Northwest Exposures: a Geologic Story of the Northwest, by David Alt & Donald Hyndman Geology Underfoot in Death Valley and Owens Valley, by Robert Sharp & Allen Glazner Stories in Stone: Travels Through Urban Geology, by David B. Williams The Presidential Range: Its Geologic History and Plate Tectonics, by Dykstra Eusden


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15 January 2011

Snowy detachment

I think snow can act as a nice analogue for larger-scale rock deformation. I explored this a bit last February, and I was reminded of it again last week, when I walked to my car one morning and saw this: Notice how the slab of snow on the hood (“bonnet” for British readers) of my Prius has slid en masse down”hill,” leaving the top portion of the hood bare of …


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14 January 2011

Friday fold(s): a few from Fossen

Norwegian structural geologist Haaken Fossen contributes two incredible images for this week’s Friday fold: a pavement of drastically-shortened banded iron formation from Minnesota, and a trio of three white granitoid dikes, buckled within a gneiss from the Jotun Nappe, in the Norwegian Caledonides. Gorgeous images of gorgeous folds, with links to the rest of Fossen’s collection.


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13 January 2011

Delicious dendrites

Hopefully seasoned readers of this blog will remember this nice chunk of limestone with pyrolusite (MnO2) dendrites growing on its surface. I took some close-ups with my Nikon microscope a few weeks ago. Here they are; enjoy! The width of the field of view in each photograph is about 1.1 cm: BTW, Mike likes dendrites, too.


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