Steam wafted over Hank Heasler as he stood on a boardwalk and watched water from Steamboat Geyser shoot into the air with an attention-grabbing "WHOOSH!"
"This could be it," the park geologist said excitedly, squinting against the morning sun at the impressive spray. But Heasler had no better idea than the tourists around him as to when the world's tallest geyser would next erupt.
Unlike Old Faithful, Steamboat is anything but predictable. It's gone as few as four days and as many as 50 years between major eruptions — noisy, powerful spectacles that can send hot water 300 feet (90 meters) or higher and churn out dense steam for hours.
Recently, though, it has been more active — its two eruptions so far this year came just weeks apart...
http://www.cbsnews.com/stories/2003/09/04/tech/main571616.shtml