USGS Lecture: When Rocks Fall and the Land Slides

USGSによる、ヨセミテ渓谷の岩崩れに関するビデオがあります。お勧めの部分は
12分24秒〜　：　1850年〜1870年代の岩崩れの記録（C. King, J. Whitney, J. LeConte, G. Clark, J. Muirらの記録などから）
21分30秒〜　：　ヨセミテ渓谷の形成の話
28分〜50分　：　最近の岩崩れについての説明と危険地域の解析。特に1996年のHappy Isle岩崩れについて詳しく述べています。
ビデオ(50分強)
USGS Western Region – Evening Public Lecture Series
”When Rocks Fall and the Land Slides”
By Gerald F. Wieczorek, Geological Engineer, and Raymond C. Wilson, Landslide Geologist
*Hear why California makes an ideal environment for landslides.
*Learn about rock falls, debris flows, and other landslides.
*There have been more than 500 documented rock falls and other slope failures in Yosemite National Park – what triggers these? How do park rangers deal with this hazard?
* John Muir gave a remarkable account of an 1872 rock fall in Yosemite Valley
* Large rock falls in Yosemite can generate ”air blasts” potentially dangerous to campers and hikers
* How did ancient glaciers help create the rock-fall hazard in Yosemite?