The Yellowstone supervolcano rose at a record rate since mid-2004, likely because a Los Angeles-sized, pancake-shaped blob of molten rock was injected 6 miles beneath the slumbering giant, University of Utah scientists report in the journal Science.
The upward movement of the Yellowstone caldera floor - almost 3 inches (7 centimeters) per year for the past three years - is more than three times greater than ever observed since such measurements began in 1923, says the study in the Nov. 9 issue of Science by Smith, geophysics postdoctoral associate Wu-Lung Chang and colleagues.
"Our best evidence is that the crustal magma chamber is filling with molten rock," Smith says. "But we have no idea how long this process goes on before there either is an eruption or the inflow of molten rock stops and the caldera deflates again," he adds.
The consequences of a Yellowstone eruption
70,000 to 75,000 years ago a supervolcanic event at Lake Toba, on Sumatra, reduced the world's human population to 10,000 or even a mere 1,000 breeding pairs, according to the Toba catastrophe theory. This eruption released energy equivalent to about one gigaton of TNT and reduced the average global temperature by 5 degrees Celsius for several years.