In the great eruption of Mount Vesuvius on August 24, in the year A.D. 79, the people of Pompeii were killed—not by scalding lava, but by suffocating ash.
Cinders and ash are produced when bubbles of gas within the magma explode, causing the magma to fragment and shoot skyward.
There the fragments cool into pellet formations. Clouds of ash and cinders can travel thousands of miles before falling to the ground.
In August 1883, the midday eruption of Indonesia’s Krakatoa—perhaps the most explosive in the last 10,000 years—produced so much ash that a thick layer coated an area of 300,000 square miles (800,000 square kilometers).
The drifting clouds can also block out sunlight. The ash from Krakatoa darkened the sky in the region for two and a half days.
Since sunlight produces so much of the world’s energy, such experiences are not only frightening, but dangerous.
For 3 years, sunsets around the world were more highly colored as a result of all the ash Krakatoa threw into the atmosphere.