This deadly mixture of ash, rock, and gas is known as a pyroclastic flow. It cascaded down the mountain at hundreds of miles per hour, instantly burying the city.

Europe's other active volcanoes, like Mount Etna and Stromboli, are located on islands off the coast of Italy. This leaves Vesuvius alone on the European mainland.

Over three million people currently reside in the surrounding Bay of Naples. This makes the area around Vesuvius the most densely populated volcanic region in the world.

Watching from afar, he noted the smoke column rose on a tall trunk before branching outward at the top, perfectly mimicking the shape of the region's native umbrella pines.