A bit more about the Yellowstone Volcano

Went looking and found this article which describes what MIGHT happen and the timeline:

Is the Super Volcano Beneath Yellowstone Ready to Blow?
About 4 miles beneath Yellowstone National Park's beautiful scenery is a forty-mile-wide chamber full of molten rock under incredibly high pressure. This magma is what powers Yellowstone's fantastic geysers and hot springs, but is it about to erupt in a cataclysmic explosion that will decimate the western United States and push mankind to the brink of extinction?

Yellowstone is the crown jewel of the United States national park system. Its mountain vistas, wildlife and geographic features are visited and admired by people from around the world. More than any of those, however, it's the park's thermo-geological features that make it unlike any other part of the globe. No place on earth has as many steam vents, hot springs and active geysers as Yellowstone.

To create these features requires two elements in abundance: lots of water and lots of heat. The water is provided by the generous rain and snow the region gets. The heat comes from deep inside the earth: volcanic heat. Though you might not be able to tell from just looking at it, Yellowstone National Park is built on an ancient volcano. Not just a regular volcano, either. It lays on top of what some people have started to call a "super volcano."

The last eruption:

Yellowstone's Catastrophic Eruption
This last happened at the Yellowstone volcano approximately 650,000 years ago. The caldera that it left is 53 miles long and 28 miles wide. In the area surrounding Yellowstone, 3000 square miles were subjected to a flow of pyroclastic material composed of 240 cubic miles of hot ash and pumice. Ash was also thrown into the atmosphere and blanketed much of North America. It can still be identified in core samples from as far away as the Gulf of Mexico.

And some hand-wringing and speculation:

Some amateur geologists connected these events with the history of the Yellowstone volcano and came to some troubling conclusions: The catastrophic caldera making eruptions have occurred. at 2.1 million, 1.3 million and 650,000 years ago. Was another one about to happen? Was the next explosion overdue?

It all depends on the chemistry of the magma. Mt. St. Helens had a lot of gases dissolved so when it went, it was like a bottle of soda that was shaken and suddenly opened. Volcanoes in Hawaii are quite different -- they have very slow and long-lasting lava flows. Four miles is a little far to drill down and see just what kind of chocolate we got with this particular box. Our town is in the blast zone of an active volcano (Mt. Baker) so this is not uncommon. Before St. Helens kicked off, scientists were assuming that Baker would be the next one to blow. There are active fumaroles at the summit.