Credit: Erik Marr
The curves, peaks and geysers of Yellowstone National Park, immortalized on film by decades of nature photographers and tourists with disposable cameras, may appear to have the permanence of a photo. But subterranean shifts in basaltic magma are changing the face of Yellowstone, meaning eventually we may have to toss out some of those Ansel Adams calendars.
Scientists at the US Geological Survey, reporting in the March 2nd issue of Nature, used satellites from the European Space Agency to track a bubble of magma on the northern rim of Yellowstone's caldera, or crater. The bubble has risen as the rest of the caldera has sunk over the past six years. This activity spiked temperatures in the park's geyser basins and led the Steamboat Geyser to spurt with uncharacteristic frequency, five times between 2000 and 2003 after a nine-year hiatus.
Advertisement
"It was an area about 40 km across that was uplifting," said co-author Charles Wicks of the USGS, describing the growing bulge at the crater's edge. "It uplifted about 120 mm over about a six year period."
Wicks and his colleagues hypothesize that basaltic magma spread out beneath the caldera, bubbling up toward potential outlets around the rim and causing the dip in the center of the caldera. But a stream of magma, about 15 to 19 km under the earth's surface, has accumulated at a clogged valve on the caldera's rim, forming the bulge. The process is somewhat similar to the way a clogged pore can cause a pimple.
"We think that this valve controls how fast the magma can go out," Wicks said. "It was restricted, and the magma inflated."
Aside from the bulge, perturbations underground have also led to increased geyser activity in the Park, according to Wicks.
"It's like if you have a slab of clay and you bend it, you see the bottom part of it compress and the top part get some little cracks and open up," he said. "So, we think that's what's happening here."
Wicks said a 10 km thick crust is bending due to this magma dip, which open up pathways in the shallow geothermal system causing geysers to burst and water temperature to rise.
While this accumulation of magma in one spot could, under certain circumstances, lead to a volcanic eruption, Wicks is optimistic that there will be no volcanic eruption.
"We think in this case the magma doesn't have a good path to the surface, so at some point, as it becomes more dense, it cools a little bit and goes back down," he said. "It would take a very strong pulse of magma to actually break through the overlying crust and cause an eruption."
Whether or not Yellowstone is about to be home to a hot pit of lava, its topography will never look the same again.