(CNN) — Here's some background information about volcanoes, mountains that open downward to a reservoir of molten rock. Facts: More than 80% of the Earth's surface, both above and below sea level, is ...

Did you know there are at least 1,350 active volcanoes around the world, and roughly 20 active volcanic eruptions on any given day? While many of them occur deep under the ocean – most volcanoes are ...