Call it an earth scientist's dream: Swarms of earthquakes are continuing to rattle Yellowstone National Park. What they're indicating is the question we're all waiting to hear an answer to.
Could it be Armageddon is on the way? True, early explorers referred to Yellowstone as the place where hell boiled up. And back in 2004 there was a made-for-TV docudrama that showed the imagined impact to the Rocky Mountain region if the park's underlying supervolcano blew its top. But no one is ready to predict that the supervolcano that created the park's unique geothermal plumbing is ready to erupt.
Still, since the temblors were first detected December 26 more than 500 earthquakes have been counted. And some have approached a magnitude 4.0 tumbler.
The University of Utah Seismograph Stations reports that as of 1800 MST on 2 January 2009, seismicity of the ongoing Yellowstone earthquake swarm continues. Over 500 earthquakes, as large as M 3.9, have been recorded by an automated earthquake system since the inception of this unusual earthquake sequence that began Dec. 26, 2008. More than 300 of these events have been reviewed and evaluated by seismic analysts. Depths of the earthquakes range from ~ 1km to around 10 km. We note that the earthquakes extend northward from central Yellowstone Lake for ~10 km toward the Fishing Bridge area, with a migration of recent earthquakes toward the north. Some of the dozen M3+ earthquakes were felt in the Lake, Grant Village and Old Faithful areas. Personnel of the Yellowstone Volcano Observatory continue to evaluate this earthquake sequence and will provide information to the NPS, USGS and the public as it evolves.
This earthquake sequence is the most intense in this area for some years. No damage has been reported within Yellowstone National Park, nor would any be expected from earthquakes of this size. The swarm is in a region of historical earthquake activity and is close to areas of Yellowstone famous hydrothermal activity. Similar earthquake swarms have occurred in the past in Yellowstone without triggering steam explosions or volcanic activity. Nevertheless, there is some potential for hydrothermal explosions and earthquakes may continue or increase in magnitude. There is a much lower potential for related volcanic activity.
Geologic burps in Yellowstone are the norm. Upwards of 2,000 earthquakes a year are monitored in the park, the Norris Geyser Basin grew a bit hotter than normal in 2003, as did the Artist Paint Pots area last May, and the caldera is pushing up at a somewhat faster-than-normal rate. And yet, the park is still there.
You can find an interesting, 4-meg article into the work of monitoring Yellowstone's slumbering volcano here. The article, by Jacob B. Lowenstern, the Yellowstone Volcano Observatory's scientist-in-charge, and Shaul Hurwitz, a USGS colleague, notes that the supervolcano that created the park's landscape had its last substantive eruption some 70,000 years ago.
Over the past 2.1 million years, the Yellowstone Plateau volcanic field has produced two of the largest and most devastating eruptions documented on Earth. When will it erupt again, or might it have reached the end of its volcanic lifetime? With extended breaks between eruptive episodes, the most recent now reaching 70,000 years, large calderas like Yellowstone present special challenges to hazard assessment. In 2006 alone, Yellowstone experienced over 1200 earthquakes, and parts of its caldera rose more than 7 cm. Yet how can we determine the relevance of this dynamism to eruptive potential? How can we know whether the volcano is recharging for future activity or simply cooling and stagnating?
Though understandably technical in nature, the article provides some interesting insights into Yellowstone's caldera and how scientists are monitoring its behavior.