Uturuncu - a new supervolcano awakening?
Much media attention has recently been given to speculations about a a "new supervolcano", Uturuncu, a dormant stratovolcano in SW Bolivia, where signs of unrest have been detected by deformation and seismic measurements.
According to scientists around geologist Dr. Shan de Silva from Oregon State University, the ground beneath the volcano is inflating and the magma chamber might be filling. Along with thousands of microquakes, this could indicate a future eruption.
A study published in 2008 revealed that between 1992 and 2006, geodetic satellite measurements recorded an ongoing 70 km wide deformation field with a central uplift rate of 1 to 2 cm/yr. This uplift, could be explained by an average magma influx of 1 cubic meters per second from a source at 17-30 km depth into a shallow reservoir. Sediment and stratigraphic studies suggest that the uplift might actually have started at the time, which would mean that the volcano has just started to be at unrest.
Persistent seismic activity adds to indications of a possible future awakening of the volcano, which has last erupted 270,000 years ago. The study revealed that there are on average 2.6 earthquakes per hour, with a maximum of 14 per hour, recorded at about 4 km depth below the center of the uplift, 4 km SW of the volcano's summit.
In their paper, Sparks et al (2008) write: "The current unrest, together with geophysical anomalies and 270 ka of dormancy, indicate that the magmatic system is in a prolonged period of intrusion. Such circumstances might eventually lead to eruption of large volumes of intruded magma with potential for caldera formation."
In fact, there are some other calderas near Uturuncu, showing that the magmatic systems here have been able to produce large explosive eruptions in the past, which confirms such potential for future eruptions. And if such an eruption is large enough, on the magnitude referred to as super-volcano eruptions, and releases tens to thousands of cubic km of magma, it would have catastrophic effects.
However, such scenario needs to be taken with caution. The likelyhood of a supervolcano eruption from Uturuncu in a near future, in our lifetime is probably more than very remote.
It is not even known with certainty whether the volcano will erupt at all again, nor whether what is causing the current changes is actually caused by rising magma, nor is it really well understood how supervolcanoes behave; a possibility is that magma cools underneath the volcano and continues to form a plutonic body.
If indeed an eruption is to be expected at Uturuncu, it seems unlikely it is going to be in a near future: after 270,000 years, it could as well take and wait a few more 1000 years, until it is ready.
Source:
R. Stephen J. Sparks and others (2008) "UTURUNCU VOLCANO, BOLIVIA: VOLCANIC UNREST DUE TO MID-CRUSTAL MAGMA INTRUSION", American Journal of Science, Vol. 308, June, 2008, P. 727–769, DOI 10.2475/06.2008.01
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