A 40 cm wide sphere of gypsum (cross sectioned), showing radial array of vast lathe like crystals. Pencil for scale.
A "daisy wheel" of gypsum, indicating primary deposition of gypsum, burial and dehydration to anhydrite, then uplift and rehydration back to gypsum. ⚒️
Yes, I think you are right. It was much bluer than the malachite we were finding, but not blue enough. Thanks!
Geologist Shawn Willsey holds up a shark tooth he found. He is wearing a YELLOW jacket and sunglasses
Shawn found a fossil shark tooth in the Tirabuzón Formation! ⚒️
A blue pebble held in a geologist's hand
Azurite pebble in Arroyo Infierno today. ⚒️
Callan holds a big bread-slice-sized chunk of selenite gypsum up in front of the Sun
Rather a large crystal of gypsum... ⚒️
Sunrise over the Gulf of California, with palm trees and nopal cactus silhouetted and left foreground
Good morning from Santa Rosalia!
Becky Dorsey, Scott Bennett, Mike Darin, and Valente Salgado Muñoz, at a restaurant wearing PVCC Geology Club t-shirts
GSA field trip leaders sporting Our Brand:
Here is a better photo of the Big Tuff Channel, with people for scale. ⚒️
🥇
🙄
Of what age? ...Are they still holes?
Annotated copy of the photograph, showing the tuff deposits in yellow, uplifted marine terraces showing as notches in the flank of the tuff, and the resurgent block in red
⚒️ annotated:
A distant volcano, next to the sea viewed from a dark cliff on which grows a palm tree
Looking North toward La Reforma volcano, which erupted at 1.4 Ma, and then since that time has seen a resurgence in its central block. The resurgence is NOT a lava dome, but an uplifted block of basement, with arc granites and overlying volcaniclastic sediments, rising like a piston since 1.4 Ma! ⚒️
An outcrop of clastic sediments, with a vertical cylindrical portion of the outcrop. Pencil for scale
An outcrop of clastic sediments, with a spongy multi-strand portion that stands out in high relief. Pencil for scale
An outcrop of clastic sediments, with a series of horizontal protrusions connected by vertical protrusions, with a pencil for scale
What do these three outcrops have in common?
⚒️
A black and white bird of prey flies by. It has a dark eye stripe
Osprey flyby, from the deck of the hotel El Morro in Santa Rosalia, Baja
🦉
#birds
Sketching a field notebook of the tuff/debris flow contact
⚒️
No. If you look carefully, the base of the channel has a couple centimeters of a thin pumice fall prior to the ignimbrite. That has been dated at 9.33 Ma.
Cliff outcrop adjacent to an arroyo with layered coarse rocks and a big smiley face shaped channel filled with a massive finer grained unit
Channel filled with welded tuff, incised into volcaniclastic debris flow deposits, central Baja. ⚒️
A hand holding a gray fine grained rock with some plagioclase phenocrysts and a tan weathering rind. In the background is an ominous but blurry mountain
Welded tuff of La Reforma volcano, with the source in the background ⚒️
Two goofy geology students point to the left as a big conical mountain looms behind them.
With La Virgen volcano (young, active) in the background, Luke and Lou point at the Tuff of San Jorge, which at 12.3 Ma, sits exactly at the moment of tectonic transition between arc volcanism (subduction) and the oblique rifting that ripped Baja off of the Sierra Madre Occidental. ⚒️
A geologist wearing a plaid shirt and baseball cap prods at a rock outcrop with his hammer while another geologist wearing a sunhat observes.
Shawn Willsey examines some interesting clasts in Miocene lahar deposits with Lou. ⚒️
Multiple geologists stand in front of an outcrop and discuss it.
Ralph Dawes talks volcaniclastics with Nik and Luke and Kevin. ⚒️
A gray rock with lots of different sized, shaped, and colored clasts, all volcanic. Pencil for scale.
Middle Comondú Group volcaniclastic breccia near the crest of the peninsula, between Santa Rosalía & San Ignacio. This is a very common lithology along our field trip route. These rocks were deposited on the flanks of active arc volcanoes in the Sierra Madre Occidental before Baja was ripped off. ⚒️
A bunch of palm trees in front of some standing water
Ignacio Springs
The kids need their toys 🙄
Callan and 3 students in a row of airplane seats smiling at the camera
On the plane to Loreto, Baja California Sur, Mexico, for the GSA Cordilleran section meeting.⚒️
Callan's hand highlights a neat fold in layered rocks of unknown identity
A #FridayFold in Franciscan mélange on Perle's Beach, Angel Island, CA. ⚒️
I'm glad Logan International Airport is promoting subatomic particles, but their typography team really needs to improve this kerning.
Blue dragonfly on a wood background
Dragonfly this morning
Dr. Mitchell Byrd*, who worked intensely for years w/ the Center for Conservation Biology @ W&M (where I had a summer research fellowship in 1993), has died. RIP to an amazing scientist & conservationist. vacremationsociety.com/obituary/mit...
* Yes, it's nominative determinism.
#birds
🦉