It’s a common early-spring phenomenon: Cold, dry air from Canada meets warm, moist air from the Gulf of Mexico. The result: massive, tornado-spawning storms. Visit the map story of the 2012 Spring tornado season, which aggregates geographic information with eyewitness videos shared via social media.

The millions of Americans own smart phones and digital cameras have transformed the way we experience disaster. These are among the many clips uploaded to YouTube by witnesses to the tornadoes that tore through the central U.S. in late February and early March 2012.