Marcus Landslide, Arizona

Scottsdale's McDowell Sonoran Preserve is home to dozens of impressive geological features.
If you didn't know it was there, you'd probably never even notice the massive rockfall area called Marcus Landslide. Discovered in 2002 by a pair of local geologists, the nearly mile-long wreckage comprises an estimated 25.8 billion pounds of rubble.
The slide occurred during the Pleistocene ice age about a half-million years ago when a colder, wetter climate may have instigated the slide that shaved 1,200 feet off the ridge line and released energy equivalent to an atomic bomb blast.