The irreverent guide to the Yellowstone Caldera

It's not THE most dangerous volcano in America, no matter what the media says. It's ranked the 21st most dangerous out of more than 164 volcanoes in America. But if it blows, it will quickly become the most currently dangerous volcano in America. It's true. The results could be devastating. More than one million dead, ash and debris that would cover more than half of the United States and a devastating black out of the sun that could last five years. So the experts say. Even worse - an eruption is overdue.

The geologic record shows that the Yellowstone Caldera has blown every 600,000 years or so over the past 2 million years. The last big eruption? About 640,000 years ago. That last eruption threw out about 240 cubic miles of ash, magma, dirt, rock and stuff. So, that's what America would be looking at this time around too. Making vacation plans? If it doesn't blow before you get there, you might have some of the last images of the park before it becomes a mudhole like Mt. Saint Helens (another North American volcano that blew in 1980.

When should we worry?

When should we should start worrying? Well heck! Start now! I am! Of course it will do you no good. But if you really want to start worrying, then wait until you hear the media talking about the presences of volcanic gases leaking from the ground and rapid changes in the shape of the ground, neither of which have been sighted-yet.

But yes, there's reason to worry. In the past few days of the new year, January 2009, scientists have seen what they're calling a "swarm" of earthquakes - more than 500, at the site - and they're not sure what it all means. On Jan. 3, 2009 an earthquake of 7.2 magnitude was reported. In a Jan. 1, 2009 memo Geologist Christopher C. Sanders posted:

"I am advising all State officials around Yellowstone National Park for a potential State of Emergency. In the last week over 252 earthquakes have been observed by the USGS. We have a 3D view on the movement of magma rising underground. We have all of the pre warning signs of a major eruption from a super volcano. - I want everyone to leave Yellowstone National Park and for 200 miles around the volcano caldera.

I worried until I saw Sanders over-the-top, cheesy, melodramatic video on YouTube. Dude. NO ONE from CNN is going to interview you. Maybe the Histronic channel...but seriously. Just talk. Drop the drama.

I'm making light of it, but yes, there is a lot going on. The University of Utah Seismograph Stations report that as of 6 a.m. MST on January 2, 2009, the earthquake swarm is continuing. Over 500 earthquakes, as large as M 3.9, have been recorded by an automated earthquake system since Dec. 26, 2008 when the swarm began.

Some of the "quakes" are little more than tremors with depths ranging from ~ 1km to around 10 km. Geologists at the site say the earthquakes extend northward from central Yellowstone Lake for ~10 km toward the Fishing Bridge area, with a migration of recent earthquakes toward the north.

More than a dozen quakes with a magnitude of M3 and greater were felt in the Lake, Grant Village and Old Faithful areas. Yellowstone Volcano Observatory personnel are continuing to evaluate the quakes and will report to various agencies like the National Park Service (NPS), The United States Geographical Survey (USGS) and the public as things evolve.

Although the earthquake swarm is the most intense seismic activity in the park for years, no damage has been reported. The swarm is in a region of historical earthquake activity and is close to areas of Yellowstone famous hydrothermal activity. Similar earthquake swarms have occurred in the past in Yellowstone without triggering steam explosions or volcanic activity. However, geologists say, there is some potential for hydrothermal explosions and earthquakes may continue or increase in magnitude. There is a much lower potential for related volcanic activity.

The image below shows an image created by Wu-Lung Chang, University of Utah, that describes the magma pocket underneath the area described as "The Fishing Bridge." in Yellowstone Park.