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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.
8 September 2017
Big earthquake in southwestern Mexico, M8.1
The M8.1 southwestern Mexico earthquake is discussed and placed in context.
21 February 2017
Q&A, episode 3
A reader asks about the use of zircons in isotopic dating, and the argument for submerged continental crust beneath Mauritius.
20 February 2017
Making “Kate Tectonics”
I recently discovered a terrific series of videos on YouTube called “Kate Tectonics.” Watch episode 2, “The History of Geology,” here, to get a taste of the series’ excellent production values and its hip, humorous style: I asked one of the creators, namesake Katelyn Salem, to share a bit of information about the series: Who’s involved in the series? The credits seem lengthy! Can you give a bit of …
25 January 2017
Y-shaped joints on a basalt flow, Lake Mývatn, Iceland
A basalt flow in Iceland shows both enticing pahoehoe and fractures with a Y-shaped intersection pattern. Comparisons to bread loaves and east Africa suggest a reason why.
15 October 2014
In search of Santorini’s blueschist, part 2: finding fault
As mentioned last week, I took a solo field trip north of Perissa, Santorini, Greece, in search of subducted rocks. The contact between the two main rock types (marble and schist) was prominent and visible from a great distance (see photos in previous post), but what was the nature of this contact? Did it represent conformable stratigraphy? Was it a fault? Here’s a closer look at the contact: In places, …
9 October 2014
In search of Santorini’s blueschist, part 1: into the Valley of the Shadow of Ash
While in Santorini, Greece, your humble geoblogger braves a warm afternoon to search the hillsides for evidence of subduction.
6 June 2012
Virginia geology on video: the Alleghanian Orogeny
Here’s another video, wherein I’ve made some improvements from the last one (reserved the lower right corner for the webcam “talking head” video inset, and adjusted the microphone for fewer audio blowouts). It’s still not perfect – there’s a disconnect between the audio and the webcam video that becomes more and more pronounced throughout the course of the video, but it’s a step in the right direction. The Alleghanian Orogeny: …
30 November 2011
Continental Drift vs. continental drift
I got this e-mail this morning from a geology colleague. I’ve despecified it and made it gender-neutral: I have a silly question about word usage and I’d love to hear your opinion. Today I overhead [a biologist colleague] talking about continental drift, and I cringed. S/he used it in context with continents moving apart and how that can alter gene populations. I shudder whenever I hear my students use conti …
24 March 2011
North Pole, South Pole, by Gillian Turner
I was sent a review copy of a new book about the Earth’s magnetism, and I finished reading it last week. It’s called North Pole, South Pole: The Epic Quest to Solve the Great Mystery of Earth’s Magnetism, and the author is Gillian Turner, a senior lecturer in physics and geophysics at Victoria University in Wellington, New Zealand. Here’s a link to the book on Amazon. It’s a book about …
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.