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Many of you have seen the various films and science programs detailing the history of the caldera of a super volcano that comprises Yellowstone National Park.  The thermal activity that produces the geysers and hot springs that give the park its distinction are the direct result of a huge magma chamber that lies under the park.

Back in 2007, National Geographic reported that:

Yellowstone National Park is rising. Its central region, called the Yellowstone caldera, has been moving upward since mid-2004 at a rate of up to three inches (seven centimeters) a year—more than three times faster than has ever been measured.

This rising of the surface lands is believed by geologists to signal a rising in the magma under the park.

Much of the park sits in a caldera, or crater, some 40 miles (70 kilometers) across, which formed when the cone of the massive volcano collapsed in a titanic eruption 640,000 years ago.

The supervolcano has produced three similarly large blasts in the past two million years, with 30 smaller eruptions since the caldera formed.

The super eruptions have occurred in the past at approximately 640,000 year intervals.

This morning the AP is reporting that:

Yellowstone National Park was jostled by a host of small earthquakes for a third straight day Monday, and scientists watched closely to see whether the more than 250 tremors were a sign of something bigger to come.

Swarms of small earthquakes happen frequently in Yellowstone, but it's very unusual for so many earthquakes to happen over several days, said Robert Smith, a professor of geophysics at the University of Utah.

The current swarm is nicely mapped at the University of Utah geological site, and you can meander through the USGS Earthquake Site to garner more information about this current swarm.

Swarms of small earthquakes happen frequently in Yellowstone, but it's very unusual for so many earthquakes to happen over several days, said Robert Smith, a professor of geophysics at the University of Utah.

"They're certainly not normal," Smith said. "We haven't had earthquakes in this energy or extent in many years."

Smith directs the Yellowstone Seismic Network, which operates seismic stations around the park. He said the quakes have ranged in strength from barely detectable to one of magnitude 3.8 that happened Saturday. A magnitude 4 quake is capable of producing moderate damage.

"This is an active volcanic and tectonic area, and these are the kinds of things we have to pay attention to," Smith said. "We might be seeing something precursory.

"Could it develop into a bigger fault or something related to hydrothermal activity? We don't know. That's what we're there to do, to monitor it for public safety."

The strongest of dozens of tremors Monday was a magnitude 3.3 quake shortly after noon. All the quakes were centered beneath the northwest end of Yellowstone Lake.

Back in March of 2006, Fox News offered a reasonably cogent explanation of the thermal and flow processes that might explain both the observed uplift, and the recent quakes.

Molten rock called magma rises from the Earth's core under Sour Creek dome, a major feature in the eastern section of the caldera.

When the magma reaches the mantle layer, six to 12 miles below the surface, it spreads like a pancake before branching off into several tunnels.

Magma flow is controlled by natural valves — one at Sour Creek dome that lets magma enter the system, and others that allow it to flow out. The outflow valve below the north rim uplift anomaly, however, can only pass so much magma at once.

Fox News was citing the journal Nature in this report.  In 2006, the following explanation of observed activity to that point was laid out as follows:

The five-inch increase at the uplift anomaly probably wasn't noticed by many tourists, but the changes in the Norris Geyser Basin were easily spotted by some.

After a nine year period of inactivity, Steamboat Geyser erupted in May, 2000, and has erupted five times since. Reaching more than 300 feet in the air, Steamboat produces the highest plumes of any geyser in the world.

Since 1989, Pork Chop geyser was active only as a hot spring, but in the summer of 2003 it reawakened as a geyser. Also that summer, several footpaths near the Norris Geyser Basin were closed because of near-boiling ground temperatures.

And a 250-foot line of new fumaroles, holes venting hot smoke and gases, formed near Nymph Lake to the north of the uplift anomaly.

"But when the [uplift anomaly] quit inflating in 2002 and 2003, the thermal unrest died off too," Wicks said. "So we think there's pretty good evidence for tying these events together."

The Science Channel will be re-airing its award winning program, "When Yellowstone Erupts" in January.  It provides both an historical overview of the geological history of the area, and predictions, based on continent wide geological evidence of ash deposits, of the catastrophic results of a major eruption.

Geologists are the first to admit that we have a very limited understanding of the dynamics of volcanic systems.  They can be caught flat footed by a sudden and unanticipated event such as the Mount Helens explosive eruptions.  But many suggest that earthquakes, reflecting magma rise, changes in the plumbing of the individual system, and redistribution of hydrothermic and venting systems can be precursors of eruptions.

There have been moderate eruptions at Yellowstone, the most recent about 70,000 years ago.  These eruptions may serve to release the pressure in the magma chamber, lessening the likelyhood of a massive eruption in the near future.  Scientists at USGS and the University of Utah (site of the Intermountain Region monitoring site) are not assigning any special significance to the current earthquake swarms.  But, the changes in activity during the past decade should not be considered as isolated events.  If a super eruption were to occur the effects on the Northern Hemisphere would be devastating, and the entire world would be profoundly effected.

Agriculture would be destroyed, transportation would be shut down, millions could die from inhaling the glass shards that comprise volcanic dust, and life on the planet as we know it would collapse.

I have been monitoring the Yellowstone events since reading of the uplift in the mid-1990's.  The earthquake activity during the past few days is of some concern. I would encourage you to consider what actions you might take to protect your family, and yourself, should a disaster of this magnitude occur.

It can't hurt to consider the unlikely.  The unlikely has a nasty way of slapping us up the side of the head when we refuse to plan

For another take on the information in this diary check out this.  

Originally posted to Granny Doc on Tue Dec 30, 2008 at 09:47 AM PST.

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