igneous
khannula | April 15, 2009The cores of mountain belts formed by continental collisions often contain metamorphic rocks, formed when sediments were buried in the collision and transformed by heat and pressure.
But the heat and pressure don't happen simultaneously - rocks can be buried (and increase in pressure) much faster than they can heat up. When the rocks are not allowed to heat up significantly, this process can create blueschists, the high pressure/low temperature metamorphic rocks formed in subduction zones. In continental collisions, subduction stops, and the metamorphic rocks sit around at depth, heating up…
khannula | March 9, 2009I had no idea there was magma beneath Socorro, New Mexico. When I read about it in this month's Geology, my first reaction was OMG WE'RE GONNA DIE!. (I've been occasionally using the electron microprobe at New Mexico Tech to look at rocks that were metamorphosed around a 380-million-year-old granite. I had no idea that the same kinds of processes were going on, right then, beneath my feet.)
The magma body is 19 km deep in the crust. That's about 2/3 of the way to the mantle - pretty far from the surface. But the effects are still noticeable, at least if you look at interferometric synthetic…
greengabbro | August 20, 2008It was hot out last weekend. Some of you might scoff at what I consider "hot", but the glorious thing about Seattle is that the entire city seems willing to join me in whining and wilting whenever the temperature breaks 80 (that's 25 of your Earth units). Naturally, I spent a lot of time thinking about ice cream.
Ice cream is an igneous rock. You begin with a liquid slurry containing a hodgepodge of chemicals, and by bringing it below its freezing point, you create something solid - or at least solid-ish. Good ice cream or sorbet needs a little give, a bit of liquid remaining between ice…
greengabbro | February 8, 2008
gabweb
Originally uploaded by kevinzim
I have a confession to make: I have absolutely no idea what this picture means. And most of you probably don't either, which is okay, because you're not running around the Internets pretending to be a geologist.
This is what's colloquially known as a thin section - a piece of rock sliced so thin that you can shine light through it, and then stare at it under a microscope until you get a headache. Minerals that look similar in a hand sample will refract light very differently in thin section, which makes it useful for obsessive mineral-identifiers.…