You are browsing the archive for igneous Archives - Mountain Beltway.
13 December 2019
Friday fold: blueschist & eclogite at Jenner, California
A pre-Fall Meeting field trip to the coast of northern California yields rare sights of garnet-bearing blueschist, plus eclogite, some pillow basalts, birds, waves, wind, and a lot of rain.
6 December 2019
Friday fold: a secret Santa rock exchange gift!
I participated this year in the Secret Santa Rock Exchange, wherein I shipped out a mystery rock to a random person, and got back a mystery rock from another random person. What fun! My mystery rock has folds in it! It’s from Matt Bruseke at Kansas State University. Check it out: Matt writes that this is a piece of the Silver City rhyolite, from the Owyhee Mountains, Idaho. The sample …
9 August 2019
Friday fold: crumpled green metavolcanics from St. Anthony
The Friday fold erupted out of a volcano, completing the second part of its two stage cooling history, then later got folded and metamorphosed. It was found atop a high cliff near the northern Newfoundland town of St. Anthony.
11 July 2019
A submarine slump complex at Sandy Cove, Newfoundland
Traveling in Newfoundland, Callan visits a seaside outcrop showing a Proterozoic submarine slump complex, overprinted by tectonic cleavage and weathered by the sea.
22 February 2019
Friday folds: Sardinian tuff
It’s the last day of the work week. Some photos of isoclinal syn-depositional folding in Sardinian tuff will get your Friday off on the right foot.
17 November 2018
Flow banding in pseudotachylyte, South Mountains, Arizona
Watch the flow of frictional melt in a “fossil earthquake,” frozen in time atop the South Mountains metamorphic core complex in Phoenix, Arizona.
1 March 2018
A GIGAmacro view of a cool outcrop in Scotland
As noted previously, the old way of viewing gigapixel imagery is no more. But there is a new, better way. The GIGAmacro company has a better viewing platform that can be used either with images uploaded to their server or with pre-existing images that currently “live” at GigaPan.com. Here’s an example: a roadcut of limestone of the Grudaidh Formation (Durness Group) in the Northwest Highlands of Scotland, near Ardvreck Castle, …
8 February 2018
A spectacular display of Earth science in the Alabama Hills
A detailed examination of an elegant photo of the eastern front of California’s Sierra Nevada, from the perspective of the Alabama Hills. How many different geologic phenomena can be packed into a single image? Let’s find out!
12 January 2018
Friday folds: Hayden Butte (“A Mountain”), Tempe
In keeping with the Arizonarific theme of this week’s posts (thanks to my participation in the 2018 Structural Geology and Tectonics Forum), I thought I would wrap up my ‘geology of the Phoenix area‘ posts with a walk I took on my last day there. This was to what Google Maps calls “Hayden Butte,” but the locals call “A Mountain.” Not “a mountain,” but “the mountain called ‘A‘.” It has …
11 January 2018
Landslide breccias in Papago Park
A visit to Papago Park, north of Tempe, Arizona, reveals hanging wall rocks from the South Mountain detachment fault, a long way from South Mountain. Also, feast your eyes on these gorgeous red sedimentary breccias, interpreted to be landslide deposits from the Neogene.
Callan Bentley is an assistant professor of geology at Northern Virginia Community College. He is a fellow of the Geological Society of America and the 2018 National Association of Geoscience Teachers' James Shea Awardee. He has also won the Outstanding Faculty Award from the State Council on Higher Education in Virginia, and the Biggs Award for Excellence in Geoscience Teaching from the Geoscience Education Division of the Geological Society of America. Callan served as a contributing editor at EARTH magazine for many years. He is Past President of the Geological Society of Washington and the Geo2YC division of NAGT. He lives in the Fort Valley of Virginia.