A hydrothermal explosion sent visitors at Yellowstone National Park running ... However, the Biscuit Basin area near Sapphire ...

The Biscuit Basin area of Yellowstone National Park in Wyoming ... which occurred near the Sapphire Pool around 10 a.m. local time. Investigators have yet to determine how much damage has occurred.

The deep Sapphire Pool about 100 yards (91 meters) away retained its usual blue hues. Park geologists were investigating what specifically happened in this case.