jd writes "Really big. By using electrical conductivity tests rather than seismic waves, geologists have remapped the Yellowstone caldera. Whilst seismic waves indicate differences in the reflectivity of different materials, it doesn't show everything and contrast isn't always great. By looking at the electrical conductivity instead, different characteristics of molten and semi-molten rock can be measured and observed. The result — the caldera is far larger than had previously been suspected. This doesn't alter the chances of an eruption, and it's not even clear it would change the scale (prior eruptions are very easy to study, as they're on the surface) but it certainly changes the dynamics and our understanding of this fierce supervolcano."