Distinctly Montana Magazine

D I S T I N C T LY M O N TA N A s FA L L 2 0 1 5 66 66 YELLOWSTONE CALDERA YELLOWSTONE HOTSPOT UPPER MANTLE MAGMA AND HEAT SOURCE RIM BOUNDARY FAULT RIM BOUNDARY FAULT EARTHQUAKES Granitic magma Basaltic magma Rising basaltic magma Resurgent dome Shallow hot water reservoirs Freshwater Freshwater Brine Brine Brittle Plastic (PARTIAL MELT) CRUSTAL STRETCHING BASALT MAGMA INTRUSION ZONE GEYERS GEYERS M O N TA N A i n 3 CAN YOU DESCRIBE FOR US JUST WHAT THE TERM "YELLOWSTONE SUPERVOLCANO" MEANS? IT'S A FRIGHTENING TERM. When a volcanic system has experienced a "supereruption" (> 240 cubic miles of erupted debris), it's dubbed a "supervolcano." Yellowstone had two such eruptions, and a third relatively large eruption, so certainly qualifies. However, there's only so much material that can erupt out of an individual volcanic system, so Yellowstone may be winding down. JUST HOW MUCH SEISMIC ACTIVITY IS THERE, AND WHAT PLANS DOES THE PARK SERVICE HAVE FOR MONITORING ACTIVITY OVER THE NEXT 30 YEARS? Yellowstone has its own volcano observatory, similar to those in Hawaii, Alaska, Washington and California. All of them are run through the USGS Volcano Hazards Program. At Yellow- stone, the earthquakes are measured with a network operated by the University of Utah. Earthquakes vary greatly, ranging from a few hundred to a few thousand in a given year. Yellowstone is an active place, so there's no doubt that monitoring will continue for the next 30 years! WHAT SIGNS ARE YOU SEEING NOW THAT SUGGEST THE VOLCANO WILL CONTINUE IMPACTING THE YELLOWSTONE GEOLOGY, LAND- SCAPE, AND WILDLIFE? For decades, Yellowstone has exhibited continual activity. Different parts of the caldera (the volcanic crater resulting from a large eruption 640,000 years ago) move up and down due to pressure from deep molten rock. Pressurization induces earth- quakes. Heat and gas escape at the many thermal areas spread around the park. All these phenomena signal the continuing activity of the volcanic system. WHAT ARE WE LIKELY TO SEE OVER THE NEXT 30 YEARS WHEN IT COMES TO THE OBSERVABLE IMPACTS OF SEISMIC ACTIVITY IN YEL- LOWSTONE? We are likely to see more of the same. Earthquakes, ground deformation, and steam explosions from the thermal areas are all likely. An actual volcanic eruption is much less likely, but not impossible. THE YELLOWSTONE SUPERVOLCANO yea rs

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