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During the month of May 2008, 99 earthquakes were located in the Yellowstone region. The largest event was a magnitude 2.3 on May 18 at 2:44 AM MST, located about 7 miles north of Fishing Bridge, WY. There was a swarm of 37 events, May 4-14, with magnitudes from -0.6 to 1.8, located anout 7 miles north of West Yellowstone, MT.
Earthquake activity in the Yellowstone region is at normal background levels.
Ground Deformation Summary: Through May 2008, continuous GPS data show that most of the Yellowstone caldera continued moving upward, though at a lower rate than the past several years. The maximum measured ground uplift over the past 40 months is ~20 cm at the White Lake GPS station.
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.
Wrinkles and Cracks
Using satellite-based radar, Wicks and his colleagues were able to map small changes in surface elevation continuously across a wide area.
The new, detailed view of the Yellowstone crater shows a surface in constant motion, rising and falling in different locations and over fairly short intervals of time. From earlier surveys, scientists know that the caldera floor raised about 7 inches (18 centimeters) from 1976 to 1984 and then settled back about 5.5 inches (14 centimeters) from 1985 to 1995.
Researchers later noted a vertical rise in the crater floor, beginning in 1995. The floor largely began sinking again by 1998.
The new report, to be published in tomorrow's edition of the journal Nature, focuses on an isolated area along the north rim of the crater that continued to rise while the crater floor was sinking.
This localized uplift raised the ground level about 5 inches (13 centimeters) from 1997 to 2003.
"This was something new," Wicks said. "We had never seen uplift under the caldera rim before."
At the same time thermal activity in and around the Norris Geyser Basin, near the uplifting-rim area, began moving into high gear.
Steamboat Geyser, the world's largest, broke a nine-year silence with a series of eruptions from 2000 to 2003.
Park officials had to close some hiking trails due to increasing ground temperatures, and in 2003 a line of new steam vents appeared, roaring like jet engines.
Wicks and his colleagues believe that a pulse of volcanic magma moving horizontally underground caused the complex rippling of the land surface and the unusual hydrothermal