How cool is this? The Smithsonian has a website dedicated to Holocene volcanoes.
Most geologists came to the philosophy from a childhood fascination with dinosaurs, and, while I think dinos are much too cool, my first interest was volcanoes. Tuzo Wilson didn't drop the plate tectonics bomb until 1963, and my exposure to volcanoes was about eight years earlier.
There was no suitable mechanism for volcanism (or earthquakes or orogeny, mountain-building), and the first story I recall was of a volcano in Mexico rising from the spot where a farmer flicked a burning cigarette stub. That was Paricutín, which last erupted in 1954, and is the image which appears on top.
Here's the link:

http://www.volcano.si.edu/

So what's so cool about volcanoes?
What J. Tuzo Wilson proposed in 1963 was hot spots, places where the crust of the earth is disturbed by a seemingly endless supply of magma (lava). When you look at a map of the Hawaiian Islands, and track the westernmost, oldest, Kure, back through the youngest, Hawaii, you can appreciate that the crust is passing over a "hot spot", which continues to throw up volcanic islands.
Another notable hot spot is Iceland. In 1963, as if to approve Wilson, Volcano Surtsey literally jumped out of the ocean.
Of more concern to us continentals is the area in south Idaho stretching into Yellowstone Park. This hot spot flooded Idaho and eastern Washington with two miles, two miles, of basalt, volcanic glass. The Snake River canyon, at over 6,000 feet deep, averages a thousand feet deeper than the Grand Canyon, but cuts through dirty brown glass, and lacks the color and beauty of 300 million years of sandstones.
There are at least three calderas, volcano basins, on a line to Yellowstone, where the latest is evident. And old.
All the geothermal activity at Yellowstone results from a hot spot, where the crust is so thin that geysers and bubbling, boiling springs are the norm.
The caldera indicates an eruption of a size to extinct the dinosaurs, and a whole bunch of other stuff.
And it may be soon. The times for each of the eruptions in the caldera chain indicate it is due.
Yellowstone Lake, situated in the center of the caldera, grows more shallow every year, grows as in the lake bed is rising.
A Supervolcano? Yeah, why the hell not. The caldera is about 50 miles across (you can measure Mt. St. Helens in yards). Coming? For sure. Soon? Probably not.
You should worry more about growing old without health insurance, and the fact people actually care what a loser quitter like Sarah! Palin has to say.