The rockfall event happened on April 11, 2009 after some moderate to significant rainfall in the area several days earlier. The source of the rock is a limestone unit some 2,600 vertical feet above the house and as mentioned, almost a mile away. The block was estimated to be approximately 4x4x5-ft. By my estimates, that’s easily over 10,000-lb in weight.
Interestingly, this is not the first rock fall to strike a house in the area. In May of 2005 a similar event slightly damaged a backyard playhouse and fence. The Utah Geologic Survey report has a nice map showing what was thought to be the path of these two rocks, and they appear to be rather similar.
More Info
- Utah Geological Survey preliminary report dated 4/16/09
- KUTV Report on the event (they appear to have overestimated the size of the boulder…they said it was 8-ft.
Map of Rock Fall Location
{mosmap width=’450px’|height=’300px’|zoom =’17’|zoomType=’Small’|zoomNew=’0’|zoomWheel=’1’|mapType =’Hybrid’|showMaptype =’1’|Overview =’2’|text =”|marker =’1’|dir=’0’|tooltip =’House hit by rockfall April 11, 2009’|address =’1496 North 1550 East, Provo, UT’|align =’center’}
A rock like that one would expect to be associated with debris so I guess this was a well vegetated slope, or just cliff and clear drop onto the roll, it must have made a mess of the scour zone, presumably a convenient garage floor as a platform has the same buffering effects as a sea cliff bench especially at raised beach, where several such fragments have been seen … Wyllie Norrisch have the Revelstoke 3 valley gap similar item lodged in the debris … did this have potential to roll farther as well ?