Volume 8, Number 43 - January 15, 2009
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Yellowstone tremors shake nerves
A recent swarm of earthquakes beneath Yellowstone National Park has caused some to worry that the area’s super volcano is coming to life.
It is the first earthquake swarm to hit the area since a three-month swarm aff ected the area in 1985. The recent episode began on Dec. 26 when the fi rst of 500 tremors shook the area. The activity died down around Jan. 1.
More than 300 of the quakes were magnitude 2 or less, while 16 were magnitude 3 or greater (magnitude 3.5 quakes are generally the smallest that can be felt by humans.) The tremors epicenters were at the north end of Yellowstone Lake. They migrated over the seven-day period from Stevenson Island to the Fishing Bridge, according to the Yellowstone Volcano Observatory (YVO).
The quakes occurred at a relatively shallow depth of 1.8 to 6.0 miles.
A second swarm was observed on Jan. 9. Ten quakes shook an area 16 miles north of Yellowstone Lake with the largest at magnitude 3.3.
The YVO says the activity is “well above typical activity at Yellowstone,” but it says the activity is not unprecedented. Over the past 40 years of observation “swarms have been the typical mode of occurrence,” the YVO reports.
The biggest recorded quake in the Yellowstone area occurred a half-century ago.
The magnitude 7.1 quake, centered near Hebgen Lake, Mont., occurred just before midnight on Aug. 17, 1959. It killed 28 people and was felt by half of Wyoming. After the quake, many of Yellowstone’s geothermal features changed with some new features popping up and older features bubbling with renewed intensity.
But it is a dramatic change in the area’s geothermal behavior that worries scientists. Yellowstone sits on one of the earth’s few “hotspots” where vast reservoirs of magma lurk at relatively shallow depths. As the earths tectonic plates slide across the earth’s mantle, the immobile hotspots scar continents, creating hydrothermal wonders such as Yellowstone and build islands such as Hawaii, Iceland and the Galapagos.
But underneath Yellowstone’s geysers and bubbling pools is an ominous fact: the Yellowstone hot spot is one of the largest volcanoes in the world.
From its current location in northwest Wyoming, the hotspot has erupted three times: 2.1 million, 1.3 million and 640,000 years ago.
Each of those eruptions dwarfed every other eruption in recorded human history. The eruption 2.1 million years ago, named the Huckleberry Ridge eruption, was so large that if it happened today it would kill millions, perhaps billions of people by choking the earth’s atmosphere with a layer of soot and ash.
Citing the pattern of Yellowstone’s eruptions, some scientists have suggested that the super volcano might be due to release another global cataclysm.
Popular television networks have fueled fears by repeatedly dramatizing the apocalyptic event in show after show.
Certainly, no Yellowstone earthquake swarm has been associated with the super volcano more than this one.
One person was so overtaken earlier this month by the hysteria, he posted a phony evacuation alert online.
Lifting information from the YVO Web site and illegally reproducing the United States Geological Survey (USGS) logo, Chris Sanders of Little Elm, Texas, posted evacuation orders on his site for a 100-mile radius around the volcano’s caldera – Daniel Junction is 113 miles from the latest earthquake swarm epicenter and within a 100-mile evacuation radius of the caldera. For his actions, Sanders faces charges of impersonating a federal offi cial and violating the USGS trademark.
Sanders’ erroneous information notwithstanding, most experts wouldn’t bet on a super eruption in our lifetime.
“The probability is extremely low,” said Seth Wittke, Wyoming State Geological Survey surfi cial geologist. “There is definitely nothing imminent that is occurring from the swarms we are seeing right now.”
Wittke said even though the timing is right in geologic terms, in human terms experiencing a Yellowstone eruption is extremely remote.
With 10,000 human life spans occurring between 640,000-year eruptions the odds that we’ll see an eruption “are pretty slim,” he said.
It is widely believed that the prelude to a super eruption would consist of gradually intensifying geologic activity for a period of decades and possibly centuries.
Wittke said the USGS is looking for changes in the park’s hydrothermal features but as of Monday, “Nothing has changed that we know of.”
Scared to no purpose
Th at leaves Yellowstone and the surrounding area pretty much where it was prior to the earthquake swarms.
But the effect on humans’ nerves might be longer lasting.
“Th is is a situation where you have absolutely no control,” Psychologist Dr. Stephen Lottridge said. “And to become anxious in a way that upsets our day-to-day lives serves absolutely no point at all.” Lottridge said children are the most likely to be adversely aff ected by doomsday predictions saying, “When kids get scared, they get scared at the world.” He suggested talking about the issue in scientifi c terms and as a natural phenomenon, and not making jokes such as, “If this thing blows we’re all going to be vapor.”
“Th ere is a kind of fatalism that comes with adulthood,” he said. “It doesn’t translate to kids and they become scared to no purpose.”
Yellowstone geologic updates are available at the YVO Web site at www.volcanoes.usgs.gov/yvo/.
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