You are browsing the archive for weathering Archives - Page 2 of 13 - Mountain Beltway.
12 April 2017
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 …
28 March 2017
A hardware parking lot in rural Virginia showcases an elegant slab of pressure-solution induced compaction of a conglomerate.
13 February 2017
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.
13 January 2017
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.
8 December 2016
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?
30 November 2016
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 …
3 October 2016
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 …
28 June 2016
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 …
25 June 2016
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.
20 June 2016
Want a geological irony? Here’s one! You’re looking at a rounded boulder of Cushendun Conglomerate, a Devonian “Old Red Sandstone” unit (Cross Slieve Group) exposed at Cushendun Caves, Northern Ireland, U.K. The irony lies in the repetition of history – a tumbling environment of high water energy, rounding cobbles and boulders and depositing them, in order to make the conglomerate. And now, ~400 million years later, history repeats itself, with …