This slim volume (130 pages of ~10 point type) is the 425th in Oxford University Press’s vast series of dense little books about various subjects. Browsing the geology shelves at my college’s library this week, I saw it and thought I might as well check it out. I’ve shifted through the years in what I … Read more
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.
The M8.1 southwestern Mexico earthquake is discussed and placed in context.
A reader asks about the use of zircons in isotopic dating, and the argument for submerged continental crust beneath Mauritius.
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: [youtube=”https://www.youtube.com/watch?v=EjnsLu6RyYU”] I asked one of the creators, namesake Katelyn Salem, to share a bit of information about the … Read more
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.
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 … Read more
While in Santorini, Greece, your humble geoblogger braves a warm afternoon to search the hillsides for evidence of subduction.
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 … Read more
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 … Read more
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 … Read more
Part 4 of the ongoing series examining the geology of the San Francisco area. In today’s post, Callan visits Kirby Cove in the Marin Headlands, where intensely deformed chert can be found on one end of the cove, pillow basalts on the other, and an “artificial dune” in the middle.
Episode three in the multi-part series on the geology of San Francisco. This post focuses on the chert layers of the Marin Headlands
The first in a multi-part series on the geology of San Francisco and the surrounding area.
The author recounts a field trip in October along the section of Turkey’s North Anatolian Fault that last ruptured in 1944. The rock types on either side of the fault are compared, offset markers are illustrated, and several types of landforms particular to strike-slip faults are shown. The post concludes with an examination of the town of Gerede itself, which is built directly atop the fault.
Picking up where we left off last time, we were in some partly-serpentenized peridotite, part of the Burham Ophiolite in Turkey’s Tavşanlı Zone, an ancient tectonic suture. Our next stop on the field trip allowed us to visit some diabase dikes: Here’s a close-up of the right contact of the dike with the host peridotite: … Read more
Before the Tectonic Crossroads conference two weeks ago, I had the good fortune to participate in a Istanbul-to-Ankara geology field examining the Tavşanlı Zone, a tectonic suture zone where a portion of the Tethys Ocean basin closed. This paleo-convergent boundary is marked by a suite of interesting rocks, including blueschists, ophiolites, and eclogites. I’d like … Read more
Over the summer, I went up to Vermont to visit my friends the Clearys. Joe Cleary is a college friend and a talented luthier. He and his wife Tree and their children Jasper and Juniper have settled in Burlington, a lively town with a lot of cool stuff going on. Joe took time out one … Read more
Ice… serpentine… halite… What do they all have in common? I’ve discussed mineral “ghosts” here before — really, those are only pseudomorphs, where one mineral’s chemistry becomes unstable due to a change in conditions, and then a new mineral forms in the same space. I’ve also brought up the issue of clasts of minerals which … Read more
We just looked at the Chilhowee Group, a package of sediments that records the transition for the North American mid-Atlantic from Iapetan rifting through to passive margin sedimentation associated with the Sauk Sea transgression. Well, if we journey a bit further west, we see the sedimentary stack isn’t done telling its story. The saga continues … Read more