Geologists working in Yellowstone National Park discovered a new pool of strange light blue water this spring. Using satellite imagery, they have now been able to determine exactly how and when this new feature was born.

Where previously there had been a rather featureless patch of ground at the northwestern tip of a landmark known informally as 'Tree Island', there was now a gaping hole about 4 meters (13 feet) wide, filled with milky, light blue water. Related: Yellowstone's Supervolcano Could Give Less Warning of an Eruption Than We Thought