The Cascadia Subduction Zone is a sleeping monster lurking just off the Northwest coast of the United States. It extends 600 miles between Northern California and Vancouver B.C. and experiences a massive megathrust earthquake every 250 years on average. The last one happened 321 years ago and scientists say there is a 30% chance we’ll see another in the next 50 years. It’s expected to rival the 9.0 quake that shook Japan for 6 minutes, which was the most destructive natural disaster in human history. It unleashed a tsunami that reached 100 feet in some areas, caused an estimated $360 billion in damages and claimed some 16,000 lives.