The earth really moves in this episode as we take in scenes and stories from some of the most devastating of all the natural cataclysms: the earthquake. With all its pent-up power, nothing releases more sheer destructive energy than the grinding forces at work between the Earth's tectonic plates.

Things get personal in this episode as we really get under the skin to explore something that is a threat to all of us wherever we live: the epidemic and its global big brother, the pandemic.

Ours is a dangerous world where geological mishaps—avalanches, landslides, heat waves, sinkholes and blizzards—can spell disaster almost as much as big cataclysms like earthquakes and tidal waves. While casualty counts might be lower, geological disturbances still cause their fair share of misery.