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17 April 2017

Liesegang rings in a natural sandstone “tile”

Liesegang rings in a natural sandstone "tile"

An easter egg on a piece of toast? No, it’s a nice example of Liesegang rings in a slab of sandstone. Explore more in this blog post.

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12 April 2017

Weathering along perpendicular joint sets, Arran

Weathering along perpendicular joint sets, Arran

Check this out: That’s a beautiful example of weathering in a dolerite dike on Arran. The igneous rock was broken along two more or less perpendicular joint sets, and then fluid flow along those fractures helped “rot” the adjacent rock through oxidation and hydrolysis. The resulting brownish weathering rind  grows at the expense of the unweathered black rock. Because there is more surface area at the corners of the rock …

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28 March 2017

P-sol in a conglomerate countertop slab

P-sol in a conglomerate countertop slab

A hardware parking lot in rural Virginia showcases an elegant slab of pressure-solution induced compaction of a conglomerate.

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13 February 2017

Q&A, episode 2

Q&A, episode 2

A new edition of “science and nature question and answer.” This week: why Massanutten Mountain isn’t longer, and why you’re never going to walk on the Sun.

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13 January 2017

Friday fold: Smaull Graywacke at Saligo Bay, Islay

Friday fold: Smaull Graywacke at Saligo Bay, Islay

On the western coast of Islay, Saligo Bay showcases turbidites of the Neoproterozoic Colonsay Group. The Smaull Graywacke shows Caledonian (late Ordovician) folding and cleavage superimposed on world-class graded bedding. There’s also a nice dolerite dike to examine.

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8 December 2016

Silent samples, holey samples

Silent samples, holey samples

Two very different samples tell stories that are full of holes. What’s going on with this weathered sandstone? What’s going on with this fossil scallop shell?

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30 November 2016

“Drumsticks” of Islay tillite

"Drumsticks" of Islay tillite

One fun thing about examining the Port Askaig Tillite in the field is to find odd-shaped exemplars of the unit lying on Islay’s beaches. My favorites were shaped like wands, or antennae, or perhaps the drumsticks freshly detached from a Thanksgiving turkey… a big clast at one end and then a thin septum of the finer-grained matrix to hang on to: Here’s an example: The shape results from differential weathering …

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3 October 2016

A virtual field trip to Rathlin Island, Northern Ireland

A virtual field trip to Rathlin Island, Northern Ireland

Rathlin Island lies north of mainland Northern Ireland, a few miles offshore. I spent three lovely days there this past summer, investigating the geology and appreciating the wildlife (puffins and other sea birds, and seals). The geology is pretty straightforward: Paleogene basalt overlying Cretaceous “chalk” (really not so chalky here – technically, it’s the Ulster White Limestone). Here’s a suite of interactive imagery that you can use to explore Rathlin’s …

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28 June 2016

“Dunbar marble” at Barns Ness, Scotland

"Dunbar marble" at Barns Ness, Scotland

Thanks to the website ScottishGeology.com, run by Angus Miller, I learned of Barns Ness, a Mississippian-aged limestone fossil site on the shore not far from where we are staying at Dunbar. We ventured out there on Saturday afternoon, in search of fossils. The presence of the Dunbar Cemenet Works nearby is an indication that this is the most extensive limestone outcrop in central Scotland. I set my field assistant loose …

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25 June 2016

A virtual field trip to the Giant’s Causeway, Northern Ireland

A virtual field trip to the Giant's Causeway, Northern Ireland

Some of planet Earth’s best examples of basaltic cooling columns are found at the Giant’s Causeway in Northern Ireland. In this post, explore four different kinds of interactive digital media as a way of experiencing the Causeway virtually, from the comfort of your computer.

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