Recent Ups and Downs of the Yellowstone Caldera
The November 9, 2007 issue of Science Magazine features an article, Accelerated uplift and magmatic intrusion of the Yellowstone Caldera, 2004 to 2006, by YVO scientists from the University of Utah and USGS.
The lead author, Wu-Lung Chang is a Post-doctoral associate with Robert B. Smith, YVO Coordinating Scientist at the University of Utah. Chang specializes in use of the Global Positioning System (GPS) to measure very small movements of the Earth's crust. Using GPS and another satellite-based technique (InSAR), the authors find that parts of the Yellowstone Caldera rose as much as 7 cm (~3") per year during the period 2004-2006. The uplift is most noticeable at the White Lake GPS station, as has been discussed in our monthly YVO updates during the past year. As of late October 2007, the total uplift since 2004 at that location is about 17 cm. Chang and his colleagues credit the relatively rapid rise to recharge of magma into the giant magma chamber that underlies the Yellowstone Caldera. They also used numerical modeling to infer that the magma intruded about 10 km (6 miles) beneath the surface.
North of this region of uplift, another area at Yellowstone has moved downward over the past three years. This north rim uplift anomaly (NUA) had risen during the period 1996-2003, when the rest of the caldera had subsided. The activity was featured in a 2006 article in Nature Magazine with lead author Charles Wicks, one of the co-authors on the new article in Science Magazine. Chang and others hypothesize that magma input after 2004 caused fracturing of the crust that resulted in release of hydrothermal fluids from the north rim area. The loss of fluid pressure then resulted in deflation, or subsidence of the ground surface.
Interestingly, the Yellowstone caldera has remained seismically quiet during the past three years of uplift. An earlier article on our website, Satellite Technologies Detect Uplift in the Yellowstone Caldera provides context on the techniques used to study these movements. The new activity, though more rapid than those previously measured at Yellowstone, is not unprecedented at large calderas around the globe. Given the absence of large earthquakes, earthquake swarms and anomalous behavior of Yellowstone's hydrothermal system (its geysers, mud pots and fumaroles), we find little indication that the volcano is moving towards an eruption. At this time, volcanic eruptions and hydrothermal explosions remain an unlikely possibility. Given the geologic history of the area, it is likely that the current period of uplift will cease, to be followed by another cycle of subsidence. When this might happen, though, is unknown.
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