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

2. 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

3. 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 100MPH
At least 2 previous slides

4. 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

5. 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 air- lubrication method
Compressed air allows for speed and distance as well as staying whole

6. 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

7. What can we learn from this?
Landslides can move really fast
Rockfall is extremely dangerous even if you are far away from it
What can we do to prevent this?

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