EARTH SCIENCE
'(<a href="http://www.j-archive.com/media/2010-03-22_DJ_16.wmv">Kelly of the Clue Crew stands in front of a map of Wyoming and Montana.</a>)  The caldera of a supervolcano that last erupted 640,000 years ago covers much of the 2.2 million acres of <a href="http://www.j-archive.com/media/2010-03-22_DJ_16.jpg" target="_blank">this</a> national park'
Yellowstone National Park