Jan. 6, 2014 — Last year's gigantic landslide at a Utah copper mine probably was the biggest nonvolcanic slide in North America's modern history, and included two rock avalanches that happened 90 minutes apart and surprisingly triggered 16 small earthquakes, University of Utah scientists discovered. The landslide -- which moved at an average of almost 70 mph and reached estimated speeds of at least 100 mph -- left a deposit so large it "would cover New York's Central Park with about 20 meters (66 feet) of debris," the researchers report in the January 2014 cover study in the Geological Society of America magazine GSA Today.
http://www.sciencedaily.com/releases/2014/01/140106094206.htm