34 Supervolcanoes, Most Could Wipe Out Millions When They Erupt

Askja Caldera (Iceland)

This Arctic wonder triggered mass emigration after its 1875 eruption. The stark landscape features lava fields surrounding blue lakes against black ash. The geothermal pool called Viti (“Hell”) draws brave swimmers despite its volcanic origin. Magma chambers still simmer below the surface. Iceland’s position on the Mid-Atlantic Ridge makes this caldera particularly unpredictable.