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Showing posts from October, 2015

Do you live near a maar volcano?

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-Alison

I am always going on about maar volcanoes. So where are the maar volcanoes? These volcanoes are formed by explosions underground occur because magma interacts with water and form unassuming craters. The craters are cut below the ground surface so their outer slopes are fairly shallow, and they are frequently filled with a lake. When there isn’t a large majestic volcano to climb and take fancy sunset photos in front of, it can be hard to get excited about what looks like a little hole in the ground. But remember, they are explosive, it takes a lot of energy to carve a big hole in the ground. I use dynamite to make craters that are only 2 meters in diameter (a tall friend lying on their side). We would need about 10,000 sticks of the dynamite we use to get close to the size of a maar volcano. I have been recently comparing the shapes and sizes of maar volcanoes around the planet. While I knew they were all over the place, I am now better informed on exactly where and how big the…

Flowing rock frozen in time at Inyo Domes, California

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- Janine

What happens when you get really viscousrhyolite (high silica content which makes it very sticky) magma rising to the surface? Well, it either stops, produces a really big bang, or oozes. When it stops below the surface it forms granite, which we see a lot of nearby in Yosemite. A build up of gasses that produces very high pressures can result in an explosive eruption, like certain eruptions that have occurred in the past at Yellowstone and Long Valley calderas. When the conditions aren't right for an explosive eruption, a more quiet 'oozing' of lava occurs at the surface that creates some really fantastic looking rocks! If you want to see a great example of rocks where you can see how they moved, head over to the Inyo domes volcanic chain near Mammoth mountain in California. The Inyo domes are near the edge of the Long Valley caldera, Yellowstone's less infamous cousin, west of the Mono domes chain.

The Inyo chain is a group of rhyolitic domes and flows that…

The eruption is how big? Deposit volume story

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-Alison

It seems obvious to say volcanoes are big, but as with anything in geology size is not immediately obvious. Volcanoes can loom over a landscape, spread ash over large chunks of the planet and even influence our climate-that all sounds big. On the scale of an individual human any eruption is big. They are frequently faster than, slower than (yes both), hotter than and physically larger than a human being. One of the exercises I use when teaching volcanology is focused on understanding just how big, "big" is. We go about this by finding things that we already understand the size and compare them to volcanoes. Like many natural processes (and humans), volcanoes and volcanic eruptions come in all shapes and sizes. If volcanoes only had one size and style of eruption our job studying them and anticipating future eruptions would be much easier.



We need to be able to put a size to volcanoes because it is one way to wrap our heads around the hazards they pose. One of the firs…