tions within the hot magma, says Druitt. “These crystals grow progressively, and as they do, their chemical composition changes according to the composition of the magma around them, and the temperature and amount of water in the magma.”
The crystals revealed that a big gob of magma — perhaps 10 percent of the magma chamber’s total contents — entered in the decades before the eruption. “Looking at the crystals in this magma, we were able to reconstruct very crudely events taking place in the last few decades prior to the eruption,” Druitt says.
That final addition probably made the magma chamber unstable, leading to the eruption, Druitt explains.
If such a late, large magma movement proves typical of super-volcanoes, that could contribute to a distant early warning system for mega-eruptions, based on more conventional methods, such as seismic monitoring.
Distant early warning
But the findings also carried a caution, Druitt says, since Santorini was apparently dormant for about 18,000 years before the last apoplectic outburst. “That is a slightly alarming result. There are lot of these big caldera systems, but most are in a stage of repose.”
The upshot is more proof that a dormant volcano can still be a dangerous one, he adds. “We can imagine that a big caldera in a remote region of the world, such as the Andes, which is not monitored very well, could reawaken pretty quickly on a human time scale.”
The crystal method gives after-the-fact data on an eruption. Current attempts to anticipate eruptions rely on data about earth shaking, deformation of the crust, and release of gases.
“It’s a very timely topic, and solid science in terms of the measurements and observations,” says Bradley Singer, a volcanologist and professor of geoscience at University of Wisconsin-Madison. “They admit that there are issues about the time scales,” largely because the diffusion of strontium and titanium is imperfectly understood in the hot magma.
The study’s title, however, specifies that the final growth of the magma chamber occurs on “Decadal to monthly timescales,” Singer notes. “It could be centuries or even longer, which implies that we’d have a longer time prior to the eruption” to worry about the effects of the rising magma.
Singer concurs on the importance of understanding the relationship of magma flows, instability and eruption, and says the crystal analysis is gaining traction in volcanology.
That’s just as well, since giant caldera-forming volcanoes may be frighteningly common. The one at Yellowstone, for example, released 1,000 cubic kilometers of rock 640,000 years ago. Wouldn’t you want to know if something like that was building on your continent?
— David J. Tenenbaum
Terry Devitt, editor; S.V. Medaris, designer/illustrator; Molly Simis, project assistant; David J. Tenenbaum, feature writer; Amy Toburen, content development executive
- Decadal to monthly timescales of magma transfer and reservoir growth at a caldera volcano, T. H. Druitt et al, Nature, 2 Feb. 2012. ↩
- Volcanology: Greek inflation circa 1600 BC, News and Views, Jon Blundy & Alison Rust, Nature, 2 Feb. 2012. ↩
- 1815: Mt. Tambora and the year without summer. ↩
- What would happen if the Yellowstone super-volcano erupted? ↩
- A super-volcano’s fallout: mass extinction. ↩
- The intense impacts of volcanic ash ↩
- Explore the world’s volcanoes ↩