The Origin of Geothermal Features in Montana and Yellowstone NP

With the recent phreatic or groundwater explosion in Yellowstone, I thought it might be a good time to share a video from a outreach presentation I gave at the UM-Missoula in December, 2023. I cover the different types of geothermal features that occur in Montana (and Yellowstone National Park), and explain the mechanisms that cause them to occur. If you would like to skip directly to the section on Yellowstone's thermal features, go to 1:08:31 in the video.

As for the recent event. The explosion is a relatively common phenomenon in the geyser basins of Yellowstone National Park. In fact, an explosion just like this one occurred in Black Opal Pool in Biscuit Basin during an Earthscope field trip on May 17, 2009. The videos of the recent eruption in Biscuit Basin is a bit larger, but looks similar. Water under pressure occurs throughout the geyser basin. If something allows rapid pressure release, the water can escape like a shaken bottle of pop that has been opened quickly. There is enough upward force to dislodge the rock and fling it into the air. It was very fortunate that the folks on the boardwalk were not closer and were not downwind of the explosion. Another point of interest in the recent eruption is that the explosion ejecta is very dark in color. This is a black glass or vitrophyric sand common in that area of the geyser basin. The 2009 explosion also ejected this black sand, so looks very familiar.