You are browsing the archive for foliation Archives - Mountain Beltway.
8 November 2019
From a creek bed in northern Colorado, the Friday fold distorts foliation in early Proterozoic quartzofeldspathic gneiss, peppered with small almandine garnets.
14 June 2019
Last weekend was the annual meeting of the eastern section of the National Association of Geoscience Teachers. On Friday afternoon, we visited Harpers Ferry, West Virginia, and my colleague Beth Doyle led a great field trip to examine the rocks exposed there. This was my favorite outcrop we saw: Here is a close up of this outcrop, which is framed by (anthropogenic) rock wall: Dipping shallowly from upper left to …
21 November 2018
Today, we take a look at the structural geology that reveals the deformation evolution (first ductile, then brittle) of the South Mountains metamorphic core complex, south of Phoenix, Arizona. Expect lots of photos of smeared-out rocks, broken by faults.
22 August 2018
A reader asks: “What is foliation and what makes it so important to the structure of rock?”
Callan answers with a lot of images of beautifully foliated rocks.
13 February 2018
Some scaly Italian limestone shows off two foliations (S and C) which reveal the kinematic motions that built the Apennines.
9 August 2017
A showcase of five new 3D digital models of awesome rock samples and outcrops, produced using Agisoft Photoscan.
21 July 2017
My friend Ander Sundell at the College of Western Idaho is the source of today’s Friday fold. It’s from somewhere in Sardinia, and I think you’ll find it visually striking: Ander says: The rocks here are Silurian phyllites generated from mudstones that were deposited on the floor of the rheic ocean basin. The color and grain size variation do an excellent job highlighting compositional layering. They were deformed during the …
3 February 2017
The edge of ancestral North America can be found in the canyon of the Salmon River in western Idaho. Folds exposed the Squaw Creek Schist near Riggins record the stresses of adding terranes on during North America’s westward movement since the breakup of Pangaea. The Friday fold crinkled up during the accretion of a terrane to the growing North American continent.
25 November 2016
At the birthplace of the term “mylonite,” we can find Friday folds hidden in the foliation.