What the world looked like 250 million years ago.
The only flood basalt in recorded history spilled 12 cubic kilometers of lava across Iceland in 1783, releasing enough gas to cause Benjamin Franklin to write about a wierd, dense "dry fog" in Europe that contained no water. The gases, containing fluoride from the eruption, settled on the pastures in Iceland, poisoning the critical sheep herds and causing starvation that killed 20 percent of the population.