Two earthquakes, three monstrous hurricanes and the North Korean missile crisis have U.S. survivalists convinced that the end of the world is nigh. And they are clearing store shelves to stock bunkers in anticipation of Earth's final chapter.

Sales of freeze-dried food, gas masks and other survival equipment have spiked in recent weeks as so-called "preppers" get ready to ride out any disaster, whether natural or man-made.

Inspiring their actions: Images of people helpless against floodwater from hurricanes Harvey, Irma and Maria and island towns obliterated by their fury. People buried in rubble after earthquakes rattled Mexico. Footage of North Korea's missiles blazing into the sky.