TIL: There is an extinct volcano sitting directly beneath the city of Jackson, Mississippi. Specifically, it is approximately a half mile below the Mississippi Colosseum and state fairgrounds. In the late Cretaceous period — about 100 million years ago — this part of North America was under water. In fact, “North America” back then was actually more like a couple of mini-continents surrounded by ocean. The Jackson Volcano was the heart of a 400-square-mile island in that sea. It hasn’t erupted in 65 million years, but the ground is still hot enough that some local wells pump up 102°F water. [Edited to add that the relationship between groundwater temp and the Jackson Volcano may not be accurate. Eric Klemetti — geoscientist and Wired blogger — told me he would be surprised if an extinct volcano was the source of that heat.]