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4 May 2012
Bancroft (a preview)
I was hoping to publish a really great set of posts on my recent trip to Bancroft, Ontario (metamorphic petrology galore), but the blogs have been having a few issues with image uploading. So until I can both upload the photos I want and have the time to comment on them properly, this will just be a teaser post with a few photo highlights.
The point of the excursion was to examine a progression of metamorphic facies formed under medium (Barrovian) pressure/temperature conditions. So our trip took us from Greenschist to Amphibolite to Granulite facies, all the way up to the point where the rocks gave up metamorphosing and just started to melt instead (migmatites!) There were also a few detours to mines because hey, mines are fun, especially when they have sodalite. And leucite crystals as big as your face.
10 November 2011
Geology for everyone! William & Mary Geology’s 50th Anniversary weekend
Two of the three William & Mary geobloggers have already posted their summaries of what went on in Williamsburg (and environs) at this weekend’s W&M Department of Geology 50th Anniversary Celebration, so it’s time for me to get cracking! (Take a look at Callan Bentley and Chuck Bailey’s posts when you get a chance, too.)
20 October 2011
“Translating” descriptions of the 1902 eruption of Santa Maria
I’ve been going through some rather old papers for the background of a manuscript I’m working on, and I’ve been finding that it’s pretty fun to read about volcanic eruptions from the perspective of early twentieth-century geologists (and non-geologists). My field area in Guatemala wasn’t considered active until Volcan Santa Maria suddenly erupted in 1902, so most people who lived there weren’t really familiar with volcanic phenomena. There weren’t any geoscientists who directly observed the eruption , but they made it to the volcano pretty quickly afterward, and collected accounts from local people to supplement their notes.
When I read these accounts, the first time through I imagine what the writers were seeing – and then the second time through I translate the account into modern terminology. One paper that this was particularly useful for is an account of the eruption written by Gustav Eisen, a Swedish PhD in biology/zoology who was living in Guatemala. Dr. Eisen is very descriptive, but to be useful for my current research, his writing needs a little interpretation. Here are some of my favorite passages, and my “translations” of Eisen’s descriptions into current terminology.
26 August 2011
Sexy Geology: Accretionary Wedge #37
Lockwood at Outside the Interzone wants to know what gets a geologist all shook up. (Hint: it’s not just earthquakes.)
Several hours of hiking on an exotic tropical island + one active cinder/spatter cone + standing on the exact spot where a fissure eruption started, that’s what!
5 August 2011
Purple everywhere! Samples from the Harding Pegmatite
All right, I’m finally getting to this post (cross-country driving trips aren’t good for keeping up with posting, apparently). My last post about the Harding Pegmatite Mine near Dixon, New Mexico had some lovely photos of the mine, but not so many of the rocks and minerals close-up. The samples I have are a little far from home (seeing as I’ve dragged them to the East coast from New Mexico), but they’re still as impressive as they were at the mine!
27 July 2011
Harding Pegmatite Mine, New Mexico
Last weekend I went on a rock-hunting trip with a group of engineers who live in my apartment complex, and on the advice of a local rafting guide (from another trip) we visited the Harding Pegmatite Mine near Dixon. The mine is no longer active (except for visits), and was donated to the University of New Mexico for educational and collecting use – and it’s pretty famous for the variety of minerals that can be found there.
17 July 2011
Left behind: Accretionary Wedge #36
In July’s Accretionary Wedge at geosciblog, we’re asked what we’ve regretted leaving behind in the field. There have always been outcrops where I’ve wished I had picked up one more sample, taken one more photo, made one more measurement – that’s probably true of any geologist. But the thing that I regret leaving behind the most is small, easily replaceable, and has only sentimental value: My first hand lens.
15 June 2011
Obsidian hunting in the Jemez Mountains
This past weekend I took a day to go revisit the Valles Caldera. While I was wandering the trails, I decided to do a little “rockhounding”. Geologists are often notorious for their rock collections, and I felt like mine was missing something that no volcanologist should be without: Obsidian.
Obsidian is basically volcanic glass – the result of lava cooling so quickly that it doesn’t have time to develop crystals. Pure glass is basically SiO2, and obsidian tends to form from rhyolitic magmas (which already have a high percentage of SiO2, typically greater than 68%). “Heavy” minerals in the obsidian (such as iron and magnesium) make the glass dark, and (depending on their oxidation state) can give it reddish or greenish hues.
26 May 2011
Weird Geology: Accretionary Wedge #34
This month’s Accretionary Wedge, hosted at En Tequila es Veridad, wants us to talk about “Weird Geology”:
Let’s face facts, people. Geology can be strange. Outrageous. Bizarre. I’m sure you’ve all run into formations and landscapes and concepts that have left you scratching your head. Maybe they got less weird later. Maybe they stayed strange. But however transient or permanent that weirdness was, it got weird. So tell us about it. Hit us with the strangest stuff you’ve got.
One location where I definitely encountered some weird geology is a field trip stop I was at several years ago in Big Bend National Park, Texas
27 April 2011
Soufriere Hills Volcano: Recent deposits in 2010 and 2011
Last year I wrote about the February 2010 dome collapse deposits of the Soufriere Hills lava dome, and this year at the SHV: 15 Years On Conference I had the chance to revisit some of the very same spots. These deposits are mainly pyroclastic material (ash, dome rock and pumice), left behind after pyroclastic flows, surges, and a 50,000 ft (~15 km) high ash plume were created during a major collapse of the lava dome. These deposits extended the eastern coastline of Montserrat almost a km in the area of the old Bramble Airport, and surges were even observed flowing out over the ocean on the eastern side of the island. Here are a few before-and-after shots of the deposits:
Jessica Ball is a volcanologist at the U.S. Geological Survey, researching volcanic hydrothermal systems and stability, and doing science communication for the California Volcano Observatory. She previously worked at the Geological Society of America's Washington DC Policy Office, learning about the intersection of Earth science and legislative affairs. Her Mendenhall postdoc and PhD focused on how water affects the stability of volcanoes, and involved both field investigations and numerical modeling applications. Her blogging covers a range of topics, from her experiences in academic geosciences to science outreach and communication to her field and lab work in volcanology.