Greg Laden's Blog

As you have surely heard, the Yellowstone Caldera ... the place where Old Faithful and the Geyser Basin reside ... has been undergoing increased "activity" including some earthquakes and a rising up of the land. Is this a big problem? Should the evacuate? Should those of us living only a few states away start wearing earplugs?

The paper reporting this, in the current issue of Science, concludes:

The caldera-wide accelerated uplift reported here is interpreted as magmatic recharge of the Yellowstone magma body. Although the geodetic observations and models do not imply an impending volcanic eruption or hydrothermal explosion, they are important evidence of ongoing processes of a large caldera that was produced by a super volcano eruption.

A little vague. I'm pretty sure, from my reading of this paper, that there is not a major imminent danger. But it is interesting to contemplate the magnitude of these things.

This volcano, the volcano we affectionately know as "Yellowstone National Park" (the caldera takes up something like a third of the park area, and is entirely enclosed within it) last erupted in a big way about 600,000 years ago. That was the third in a series of "giant eruptions." Subsequently, there were several smaller volcanic eruptions, the most recent being about 70,000 years ago.

A caldera is a hole left behind when a very large and explosive volcano blows everything out more or less at once. As calderas go, Yellowstone is on the list of the largest known. Here is a rough outline of the Yellowstone Caldera very approximately superimposed over New York City:

Here is a little historical perspective, a list of exenmlar volcanic eruptions of this type (leaving a big caldera, ejecting lots of stuff).

Tambora, Indonesia

192 years ago, a mere 30 or 40 square km in area, ejected about 100 cubic km of stuff.

(About ten other similar sized eruptions have happened during the last 10,000 years, Tambora possibly being the largest.)

Toba, Sumatra

71,000 years ago, about 3,500 square km in area, ejected about 2800 cubic km.

Yellowstone

600,000 years ago about 4,000 square km in area, about 1,000 cubic km ejected.

La Garita, Colorado

28,000,000 years ago, about 2,600 square km in area, about 5,000 cubic km ejected (possibly the largest volume of any known volcano)

So, as you can see, the Yellowstone Volcano was a doozie. Comparatively speaking.

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Source:

Chang, W., Smith, RB., Wicks, C. et al.. (2007). Accelerated uplift and magmatic intrusion of the yellowstone caldera, 2004 to 2006.. Science 318, 952-956.