Eerie Eruption, Slippery Slope, Downstream Disaster

A deadly cloud of toxic gas and ash overwhelms hikers following a volcanic eruption at Japan's Mt. Ontake in this action-packed episode. In Russia, a tornado strikes without warning and cameras capture the devastation left behind. In Vietnam, Typhoon Haiyan carries chaos downstream when a huge barge breaks free of its moorings. Plus, a snowmobiler tries to tackle an 850-meter hill in Greenland, a 73-year-old hang glider faces danger in California and South America's biggest cat demonstrates incredible hunting skills in Brazil.