Next time you see one of those Falling Rock signs along the highway, pay attention. Sometimes the rocks look like this:
Monday along I-70 in Glenwood Canyon west of Denver, there was a rock slide, to put it mildly. Some of the errant boulders were bus-sized. They punched holes through two lanes of bridge decking and shattered across all four lanes. Luckily the slide occurred during the night, when traffic is lighter, and no one was injured.
A 17-mile stretch of the Interstate is closed now, and no one knows when it will be re-opened. Because the area is in a narrow canyon, no nearby detour is possible, so a daily average of 25,000 vehicles will be forced to drive some 200 miles out of their way.
Yep, those signs are in ALL CAPS for a reason.
Update, March 10: Nature has a cruel sense of humor. Today a woman riding in a car along one of the I-70 alternate routes was killed when a basketball-sized boulder smashed through the roof of the car.