I'm fascinated by mass extinctions. Our most recent close call happened about 70,000 years ago - with the eruption of a volcano on the island of Sumatra. According to discovery.com, this explosion "caused global disruptions to ecosystems, reducing humanity to a few pockets of people -- perhaps 10,000 individuals in all. Though this is not considered one of the 'big five' mass extinction events, it was almost our own 'big one' and underscores the power of nature to wipe out species with little notice."

The last mass extinction was at the end of the Cretaceous period, 65 million years ago. Something killed a full half of all the living creatures here on planet Earth, the most famous of which were the dinosaurs.

The usual suspects causing extinctions include: volcanic eruptions, asteroid & comet impacts, climate changes, sea level changes, and changing levels of oxygen in the atmosphere. Many credible sources name volcanoes as the most likely cause, both in the past and in the future.

Will the US be wiped out by an eruption of Mount Yellowstone? Sure, it could happen. Especially because researchers have discovered that earthquakes have the power to intensify and prolong volcanic eruptions... and Yellowstone is on a fault line.

And don't forget, it wasn't just the Mayans who chose that particular date. Nostradamus predicted major events (that have since happened) in addition to the idea that the end of the world will happen in 2012.

sources:
http://dsc.discovery.com/earth/wide-angle/mass-extinctions-timeline.html
http://science.nationalgeographic.com/science/prehistoric-world/mass-extinction/
http://www.pbs.org/wgbh/nova/sciencenow/3318/01.html
http://www.livescience.com/environment/070410_quake_eruptions.html

According to Bob Smith, University of Utah's expert in Yellowstone's volcanic activity, an eruption is not imminent, because of the depth of the magma.

The National Park Service concurs that there is no evidence of a impending eruption, going so far as to say there has been no significant changes since monitoring began thirty years ago.

http://www.theepochtimes.com/n2/content/view/49964/

From the Discovery Channel feature, "Super Volcano" here is another reassuring quote:

---quote---
"Though Yellowstone could erupt again someday, there is no evidence that the caldera is readying for another massive blast, says Smith. That outlook is shared by Jake Lowenstern, the U.S. Geological Survey's lead geologist at the Yellowstone Volcano Observatory.

Volcanologists with the U.S. Geological Survey believe that supervolcanoes are likely to give decades — even centuries — of warning signs before they erupt. The scientists think those signs would include lots of earthquakes, massive bulging of the land, an increase in small eruptions, "swarms" of earthquakes in specific areas, changes in the chemical composition of lavas from smaller eruptions, changes in gasses escaping the ground and, possibly, large-scale cracking of the land.

None of those indicators are present at Yellowstone, says Smith."

http://dsc.discovery.com/convergence/supervolcano/under/under_02.html

---/end quote---

The U.S Geological Survey maintains Volcanic Observatory at Yellowstone, and publishes a Monthly Status Update. This is the most up to date and accurate information available. The current alert level is Normal, with a color code of Green, lowest level possible.

http://volcanoes.usgs.gov/activity/status.php

So, while the media and docudrama producers make money by creating panic driven frenzy, there is not one single expert that will verify the notion that conditions at Yellowstone are anything but normal. The likely hood of an eruption stand at 1 in 730,000, or .00014 percent.

The Mayans may be right about 2012, at least they don't have to worry about being upstaged in 2011 by a Yellowstone eruption.

Additional source:
http://news.nationalgeographic.com/news/2009/12/091215-yellowstone-volcano-magma-plume-larger.html

I imagine 'brink' of eruption is meant to geological terms, which is us is several generations and probably much longer.