In late spring or early summer of 2012, a flood originated at a small moraine-dammed lake on Three Finger Jack volcano in the Mount Jefferson Wilderness. Channel erosion or slope collapse breached a natural dam, draining half the lake volume. The resulting debris flow formed a bouldery deposit for about a quarter mile (0.35 km) downslope. As Cascade Range alpine glaciers shrink in size and average annual temperatures rise, lakes have formed in deglaciated areas. Those dammed by unconsolidated moraines are susceptible to breaching and pose flooding hazard downstream. Read about the event, Debris flow from 2012 failure of moraine-dammed lake, Three Fingered Jack volcano, Mount Jefferson Wilderness, Oregon.
Debris flows are water-saturated masses of soil and fragmented rock that can rush down mountainsides, funnel into stream channels and inundate valley floors downstream. These flows can be devastating to people and property. In a recent documentary, NOVA explores events before, during and after the March 22, 2014, landslide near Oso, Washington as well as other landslides from around the world, to find out why these events occur and what can be done to mitigate the hazards. View the program, Killer Landslides, online. Watch what happens when scientists conduct their own debris flow experiments at the USGS debris-flow flume.
In the early morning hours of September 23, 2004, a swarm of small-magnitude earthquakes about half a mile below Earth's surface marked the reawakening of Mount St. Helens. On October 1, 2004, the first of several small explosions shot a plume of volcanic ash and gases skyward. A growing welt beneath Crater Glacier heralded the rise of semi-solid magma that erupted onto the surface, forming rocky spines, smooth-sided ridges, and jumbled piles of lava over the next 34 months. During the eruption, scientists made important strides in volcano monitoring, developing new tools for investigation and insight into eruptive behavior. View the 2004-2008 Mount St. Helens Eruption video and read about the eruption in the 2004-2008 event timeline and statistics.