Sunday, December 18, 2011

Carbonatite lavas of Ol Doinyo Lengai --with the actual movies this time!

I  Finally figured out how to embed YouTube clips! The original version only showed complicated html coding, so I deleted that. Now back to the show:

Hello readers!

A short (I have exams to proctor and grade) blog update to post some cool YouTube fottage of Ol Doinyo Lengai in Tanzania Africa and its unique eruptions of caronatite lavas. Whereas 99.9% of of lavas that are issued worldwide is modeled based upon the silica [SiO4] tetrahedra, carbonatite is principally composed of carbonate minerals. Dawson and others (1990) documented abundant phenocrysts of the rare alkali carbonate minerals nyerereite an gregoryite while noting the conspicuous absences of any major silica phase during the November 1998 activity. The temperature of these lavas are quite low during effusion: less than 600°C, (Dawson et al., 1990)!

Enough of mew talking: click on the film clips below and try to convince yourself that you are seeing competent lavas and NOT muds oozing, flowing or burping out of the volcano!

Small roiling lava pond:

Carbonatite lava channel:

Carbonatite spattering:


Dawson, J.B., Pinkerton, G.E., Norton, G.E., Pyle, D.M., 1990. Physiochemical properties of alkali carbonatite lavas: Data from the 1988 eruption of  Oldoinyo Lengai Tanzania: Geology, 18, pp. 260-263

Saturday, December 10, 2011

Accretionary Wedge #41: My response

Im Back!

Ron Schott over at Geology Home Companion is hosting the 41st round of the Accretionary Wedge, where he wants participants to describe the most memorable geologic event that one has experienced. What follows is my contribution:

For my grade 10 Social Studies class, one of the requirements thereof was to write a paper about some culture. I chose to write about the Maori people of New Zealand. One class period was reserved to work on the report in the computer lab while the teacher roamed around, in case students needed help. I, on the computer just as you walk inside the lab and a hare to the right, asked the teacher to come over for help with ideas as I was experiencing writer's block. We had a great discussion and bounced ideas off each other for several minutes, when it happened.

What happened, exactly? The setting was a high school in Beaverton, OR (a southwestern suburb of Portland) on the afternoon of February 28th, 2001. If the date and location sound sort of familiar, I am referring to the M6.8 Nisqually Earthquake that struck the Pacific Northwest. The hypocentre of the earthquake according to the Pacific Northwest Seismic Network's data page, was situated 52 km at depth with the associated epicentre ~18 km NE of Olympia.

This earthquake was my first earthquake I have felt in my life at that point and so for the first few seconds, I wasn't sure what was going on. The ground started rolling like broad waves and confusion amongst my fellow students and the faculty present in the computer lab was quite evident. The earthquake itself lasted, I venture, 15-30 seconds and fits most closely to a III or IV on the Modified Mercalli Intensity scale where I was located at the time.

A few second's after the shaking stopped, the Principal of the school along with the campus safety person stepped foot in the computer lab and announced "May I have your attention? For your information, yes we did experience an earthquake. Please duck and cover," or something to that effect. What occurred soon after the duck-and-cover exercise I cannot recall, but I do believe we were let out of school early and in my case went home and  watched the news reports on the damage to the Puget Sound area while talking to my parental units about our collective experiences. An event I will never forget.

~Cole G. Kingsbury