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You are browsing the archive for 2016 July.

29 July 2016

Friday fold: Lewisian gneiss near Tarbet, North-West Highlands, Scotland

A quick Friday fold here from the North-West Highlands of Scotland: These are Lewisian gneisses exposed on a headland northwest of the little outpost of Tarbet (where the Handa Island ferry departs from). I was out there in search of shear zones, but I found plenty of nice folds, too. There are two main folds in the image – a synform in the foreground (yellow), and an antiform in the …

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28 July 2016

Currents of air and water, deposition and erosion

Yesterday I showed you two scenes, depicted in two photos each, that I saw on the beach at Machir Bay, Islay, last week. I suggested that it might be fun to compare and contrast them. Scene #1 was this: Scene #2 was this: Scene #1 is a place where aeolian (wind) currents were at work. They appear to have stripped away some of the sand protecting these pebbles, and then …

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27 July 2016

Compare and contrast: pebbles on a beach

Here are two scenes, depicted in two photos each, that I saw on the beach at Machir Bay, Islay, last week. Compare and contrast them. Scene #1: Scene #2: What stories do these pebbles tell? Answers tomorrow…

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22 July 2016

Friday fold: The walls of Scalloway Castle

When in Shetland, one of my first stops was the museum in Scalloway, and one of the ancillary benefits of visiting there is the castle next door: Scalloway Castle includes building stones derived from the local limestone – a Neoproterozoic unit that has recently been chemostratigraphically correlated with Snowball Earth cap carbonates elsewhere in the world. But that need not concern us today. Today we are here for the folds! …

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11 July 2016

Kilometer to millimeter: 4 GigaPans to zoom in on Lewisian gneiss

I’m in the North-West Highlands of Scotland, enjoying spectacular geology and less-than-spectacular weather. I’ve been fairly productive on the GigaPan front, regardless, nipping outdoors when the weather permits to shoot outcrops and landscapes. One set I’m particularly pleased with is this suite of four images. They show the Archean-aged Lewisian gneiss, the oldest rock unit in the North-West Highlands, as exposed on a beachside outcrop east of Durness, Sutherland. The …

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8 July 2016

Friday folds: Kinkell Braes, Scotland

When I took you on a virtual field trip to Kinkell Braes earlier this week, I didn’t mention that the sandstones are folded there, now did I? Let me remedy that omission now: That is a plunging anticline that you could actually take a plunge into: And here’s a syncline to match. Happy Friday. Hope your week was a good one, and that your weekend is even better.

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7 July 2016

Tombolo at St. Ninian’s Isle, Shetland

I came to Shetland for the rocks – but I’ve been surprised and delighted by the huge range of interesting coastal geomorphology to be seen here too. I’ve never seen so many sea stacks, wave-cut cliffs, and bayhead bars in my life. One that is so “classic,” so “textbook” that I couldn’t resist it, is the tombolo that connects St. Ninian’s Isle to mainland Shetland. In Google maps, it couldn’t …

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4 July 2016

Virtual field trip to Kinkell Braes, Scotland

Walking along the shore east from St. Andrews, Scotland, along the seaside sandstones of Kinkell Braes, you encounter several extraordinary examples of geology. It’s a great place for the next stop on our Grand Tour of the geology of the British Isles. Here’s the scene: The first stop is a giant eurypterid trackway, potentially the largest invertebrate trackway in the world (Whyte, 2005), on the underside of an overhanging sandstone …

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1 July 2016

Friday fold: Clarely, an anticline

Eric Pyle sent in today’s Friday fold – Eric reports that you can find this fold seaside, near Poulatedaun, Co. Clare, Ireland. Thanks for sharing, Eric!

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