2. West Coast Superquakes

The West Coast is home to the infamous San Andreas fault, stretching for almost a thousand miles beneath the feet of millions of Americans. But just north, there's a larger fault that could trigger a megaquake, wreaking havoc from California to Canada.

3. Miami Sinking

The coastal metropolis of Miami faces a triple threat of crumbling limestone bedrock, ferocious superstorms and relentless rising oceans.