NOVA

The history of North America since the arrival of humans is chronicled. Natural resources, including gold and oil, have enabled humans to transform the land almost as much as the geological forces that created it. However, geology may, some day, play another role in reshaping the continent: the Cascadia fault line in the Pacific Northwest could unleash a massive earthquake and tsunami; and the super-volcano beneath Yellowstone could obliterate half the continent if it erupts.