Yellowstone is rising

If you haven't yet visited Yellowstone National Park, move it to the top of your list this summer. Not only is the nation's oldest national park amazing for its vistas and abundant wildlife, but also for its hardly-slumbering monster of a volcano laying below the park.

Yellowstone sits square on top of this active volcano, one of the world's largest, and one fully capable of playing havoc with much of North America. That is why scientists keep an eye on it using a network of seismic and GPS sensors.

Professor Emeritus Robert Smith, a geophysicist with the University of Utah, says, "We monitor it in real time for earthquake swarms and ground deformation."

Ground deformation? Oh, yes. He says the park is in constant motion. You can't see it, but the ground is moving up and down as fiery hot magma pushes against the Earth's thin crust. It is this hot magma that makes all the park's geysers blow.

The changes are most evident at the Norris Geyser Basin, where the surface changes daily from the heat coming from the volcano gurgling under your feet.

Beginning in 2004 the volcanic pressure caused an amazing rise at the park -- three inches a year for five years.

Professor Smith says, "That's a lot of uplift and it's over an area that's over the entire Yellowstone caldera." The Caldera is the crater at the center of a volcano, and Yellowstone's is 50 miles long. That's right--50 miles!

And when the center bulges up, it creates a slope downward from the center of the bulge, so much so that Yellowstone Lake has tilted enough that its water has flooded out trees on the south arms.

And now, the ground is sinking.

And the drop has brought up a whole new set of questions for scientists, who say that it is like a doctor monitoring a patient. The patient takes a deep breath (between 2004-09) and is now letting it out. That much is clear from the observations.

The unanswered question is, "why?"