One less thing to worry about in 2025: Yellowstone probably won’t go boom

Although they collectively contain a lot of molten basaltic material (4,000 to 6,500 cubic kilometers), its concentration is not very high. Instead, it is mostly relatively small volumes of molten material moving through cracks and faults in solid rock. This keeps the concentration of molten material below that needed for eruptions.

After two streams of basaltic material merge, they form a reservoir containing a significant amount of molten crustal material, that is, rhyolite. The amount of rhyolite material here does not exceed 500 cubic kilometers, so it could trigger a large eruption, although small by historical standards of Yellowstone. But again, the proportion of molten material in this volume of rock is relatively small and is not considered likely to erupt.

From here to the surface, there are several distinctive features. Relative to the hot spot, the North American plate above is moving west, which historically meant that eruptions moved from west to east across the continent. Accordingly, a pool exists to the west of the bulk of the near-surface molten material that appears to be no longer connected to the rest of the system. It is small, containing only about 100 cubic kilometers of material, and is too dispersed to support a major eruption.

Future risks?

There is a similar near-surface blob of molten material that may not currently be associated with the rest of the molten material south of it. It is even smaller, probably less than 50 cubic kilometers of material. But it’s just below a large drop of molten basalt, so it’s probably receiving a fair amount of heat. This location also appears to have been the cause of a recent major eruption in the caldera. So while it may not trigger a major eruption today, it is impossible to rule out the site in the future.