Joni sits down next to me. She opens a book and points to a photo of a steamy place.  It looks like another planet. It reminds me of a Star Wars movie. The place is Yellowstone National Park in the state of Wyoming. Yellowstone was established in 1872. It's the oldest national park in the world. Yellowstone is actually an active crater in the mountains. It last erupted more than 640,000 years ago. Nowadays steamy water comes out of the ground from what are called geysers. The water smells like rotten eggs. Scientists think the crater will erupt someday, they just don't know when.