The Blackhawk Landslide Lucerne Valley California By Matt

The Blackhawk Landslide Lucerne Valley, California By Matt O'Hare

Geology of the Area Mountain is a resistant mass of marble thrust northward over uncemented sandstone and weathered gneiss. Top of mountin is 6800 ft high Extensive large scale faulting North side of mountain falls 3000 feet in a mile Uplift of Blackhawk mountain occurred in two stages Over thrusting from the south Monoclinal folding along a northwest trending axis

Slide evidence Alluvial fan at foot of mountain is 100 ft thick, 2 miles wide, and 5 miles long Striation evidence shows the landslide moved as almost a nondeforming mass of breccia at nearly 100 MPH At least 2 previous slides

More slide facts Slide is 30 ft thick at terminus, 100 ft thick at base 10 billion cubic ft or 700 million tons of crushed marble One of largest ever in north america

How did the slide move so far? Was not internally lubricated or slow moving like mudslides Water lubrication possible but would require massive rains Possibly airlubrication method Compressed air allows for speed and distance as well as staying whole

Air-lubrication method Slide launched off step about 200 feet high Trapped air and compressed it upon landing Sandstone and gneiss weathered away to leave precarious slope Would have supported speeds up to 270 MPH

What can we learn from this? Citations

Citations Monastersky R. (1992) When Mountains Fall. Sci. News 142, 136 -138. Rodrigue, Frank; (2003) The Blackhawk Landslide. Shreve, Ronald; (1959) Geology and Mechanics of the Blackhawk Landslide, Lucerne Valley, California Institute of Technology.