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You are browsing the archive for March 2011 - Mountain Beltway.

31 March 2011

Mount Washington 4: folded granite dikes

We now return to Mount Washington, New Hampshire, where our intrepid heroes summit the mountain in a mere three hours (from Pinkham Notch via the Lion Head): To refresh your memory of the story so far, we had seen metamorphosed turbidites, like this one (new image): …and checked out some gorgeous metamorphic porphyroblasts of “pseudoandalusite,” like these (new image): … and some lovely folds in the metamorphic foliation. Now we …

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30 March 2011

Rusty rinds on peely rocks

Another group of interesting cobbles from the same sand and gravel pit that I described earlier in the week: Here’s the same sample, gone all animated, for your perspectivizing pleasure: What we’re seeing here is some fine-grained gray colored rock (siltstone, I guess?) that’s developed a pronounced weathering rind marked by a large amount of rust. This rusty rind is tougher than the original, unaltered rock, and it peels off, …

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29 March 2011

Tillite in outwash

Hoo boy. This one made me yelp… While on the glacial geology of western Pennsylvania trip last Saturday, we visited a gravel quarrying operation. The operators were extracting gravel from a glacial lake delta deposit, and it was full of glacial outwash — sediments washed out from the melting front of the Erie lobe of the Laurentide ice sheet. We were there to look at the Pleistocene features, but several …

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28 March 2011

A glacial delta complex in western Pennsylvania

A week ago Saturday, my three Honors students and I went on a field trip led by Gary Fleeger of the Pennsylvania Geological Survey, to examine some cool glacial features in western Pennsylvania. The trip was associated with the joint meeting of the northeastern & north-central sections of the Geological Society of America, held in Pittsburgh. My favorite part of the trip was examining a glacial delta complex near Jacksville, …

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25 March 2011

Bulletin board

A few items for your perusal… Simon Winchester wrote an article that made a lot of geologists cringe; then he wrote another that dug the hole deeper. If you haven’t been following the conversation on Twitter, then you can play catch up. Some of us geobloggery types are submitting a letter to the Newsweek editor and one of the authors Winchester cites (while misspelling her name) is writing to the …

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Friday fold: conference samples

At last weekend’s northeastern / north-central GSA meeting in Pittsburgh, David Saja of the Cleveland Museum of Natural History presented a talk entitled, “Geometric Analysis of Folded Greywacke Layers from Pacheco Pass, California.” [Abstract link] In addition to the standard PowerPoint presentation that 99% of GSA speakers use, David also brought in some hand-samples (what we in the business like to call pocket folds) to display. As his title implies, …

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24 March 2011

North Pole, South Pole, by Gillian Turner

I was sent a review copy of a new book about the Earth’s magnetism, and I finished reading it last week. It’s called North Pole, South Pole: The Epic Quest to Solve the Great Mystery of Earth’s Magnetism, and the author is Gillian Turner, a senior lecturer in physics and geophysics at Victoria University in Wellington, New Zealand. Here’s a link to the book on Amazon. It’s a book about …

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23 March 2011

The visitors

Visitation statistics for Mountain Beltway over the past month and a half. Interesting to think about the implications… Should I do more current events blogging?

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Shear band in a granite

Walking back to my hotel after departing the Northeastern / North-central GSA section meeting on Sunday, I noticed this fine shear band cutting across a polished slab of granite on the exterior of an office building in downtown Pittsburgh: You’ll notice some grain-size reduction along that shear zone, and what looks to be a decent S-C fabric developed, with a sense of motion of top-to-the-left. If you look at the …

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22 March 2011

Glacial cobble

Saw this beauty on a field trip Saturday, examining the glacial geology of western Pennsylvania. Note the faceted surfaces and profusion of scratches of multiple sizes in multiple orientations.

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