Mother Earth slowly reveals her secrets, and this time, it’s a fault line deep in the belly of the planet. Its name is a whopper: The Cascadia subduction zone. Its gargantuan size and potential power amaze earthquake experts, who say it could cause the worst natural disaster in the history of North America — if it ruptures entirely. This quake-maker sits at the bottom of the Pacific Ocean, where the seabed meets the North American tectonic plate.

In all, it stretches 700 miles along the Pacific Northwest, from British Columbia’s Vancouver Island to Washington to Oregon to northern California’s Cape Mendocino. In fact, “the Cascadia” already has made history, causing the largest earthquake in the continental United States on January 26, 1700. That’s when the Cascadia unleashed one of the world’s biggest quakes, causing a tsunami so big that it rampaged across the Pacific and damaged coastal villages in Japan. READ MORE