Some Famous Rockfalls in Zion National Park
7,000 years ago, referred to as the Sentinal Slide, a slide occurred forming a lake at least 350 feet deep and perhaps three miles in length.
A rock fall occurred at Red Arch Mountain (above the present-day Grotto Picnic Area) around 1880, causing the enlargement of the arch and covering a spring.
60,000 tons of rock fell in 1958 over one of the windows of the Zion-Mount Carmel Tunnel.
5,000 tons of rock at the end of the Narrows Trail on August 1, 1968.
A large slide from Bridge Mountain occurred in December 1990, across from the Human History Museum.
The 1995 landslide
At approximately 2:00 am, April 12, 1995, a naturally occurring landslide blocked the Virgin River in Zion Canyon about 1/2 mile north of the main park road. The slide, over 500 ft long, consisted of over 100,000 cubic yards of rock and soil that slid down the steep, west embankment of the Virgin River, completely damming it. As a result, a lake began forming behind the slide. Following the path of least resistance, the river carved a new course through the roadbed, washing away 200 yards of the upper canyon road. About 430 people were trapped at Zion Lodge, upstream from the landslide, until an emergency detour road was carved from the east wall of the canyon adjacent to the new course of the river. This took 22-hours to complete.