The highest ever-measured seismic wave on Earth 524 metres (1720 ft), occurred here in Alaska, in Lituya Bay, in 1958. Because of the harshness of our climate in the sub-Arctic and Arctic, and strong geological forcing, being on one of the "Ring of Fire" tectonic plate boundaries, Alaska is prone to dramatic natural events. No better illustration of which has just been publicised today, not too far from the great event of 1958, although it actually occurred several weeks ago!
http://en.wikipedia.org/wiki/1958_Lituya_Bay_megatsunami
Last month a huge 2200 metre tall (7216') section of 3430 metre (11,250') Mt. Lituya collapsed and ran out as a 9 km (5.5 mi) long slurry of rock/ice onto Johns Hopkins Glacier, which empties into Glacier Bay, and is in world-reknowned Glacier Bay National Park. What we were especially struck with, and in awe of, at the Alaska Progressive Review, is that although it was detected by seismometers in Canada in real-time, it has taken weeks for a real report of what occurred there, to be gathered.
Because of the remoteness, steepness and rock/ice cover of this area, combined with often foul weather and incredible snow/ice loadings, few or no people are ever on the ground here, at any time of the year. And, because of this constant parade of weather systems moving through from the nearby Gulf of Alaska (this is one of the wettest areas in the northern hemisphere), "bad" or less than visual flight rules (VFR) flying conditions are most often present in this region.
Give this article a read, from our local Anchorage Daily News, it's very interesting, and has some excellent photos of the slide, from a pilot who has flown in there. Then we'll offer some more information we have about this event.
http://www.adn.com/2012/07/12/2539823/massive-southeast-landslide-covers.htmlPark landslide covers glacier, triggers earthquake monitors
Results of cliff collapse in park showed up as 3.4-magnitude earthquake.
Published: July 12th, 2012 09:45 PM
Last Modified: July 12th, 2012 09:46 PM
Last Modified: July 12th, 2012 09:46 PM
Even by Alaska standards, the rock slide in Glacier Bay National Park was a huge event.
It was a monumental geophysical event that was almost overlooked until a pilot happened to fly over where the cliff collapsed and snapped some photographs nearly a month later.
When the cliff collapsed in the national park in Southeast Alaska on June 11, it sent rock and ice coursing down a valley and over a glacier in what perhaps was the largest landslide recorded in North America.
The rumbling was enough so that it showed up as a 3.4-magnitude earthquake in Alaska. The seismic event also was recorded in Canada. The massive landslide occurred in a remote valley beneath the 11,750-foot Lituya Mountain in the Fairweather Range about six miles from the border with British Columbia.
"I don't know of any that are bigger," Marten Geertsema, a research geomorphologist for the provincial Forest Service in British Columbia, said Thursday when comparing the landslide to others in North America.
If someone had been standing in front of the slide, the air blast alone would have flattened that person, said Geertsema, who studies natural hazards resulting from geophysical processes on the Earth's surface.
"I think they would be blown over by the air blast," he said.
Despite the extraordinary size of the landslide, which was estimated at a half-mile wide and 5 1/2 miles long, it went virtually unnoticed until air taxi pilot Drake Olson flew over it on July 2. The landslide, which rolled over the glacier, is not very noticeable to the thousands of cruise ship passengers who visit Glacier Bay National Park near Juneau each summer. That is because it is about 12 to 15 miles up the glacier from the bay.
Despite the extraordinary size of the landslide, which was estimated at a half-mile wide and 5 1/2 miles long, it went virtually unnoticed until air taxi pilot Drake Olson flew over it on July 2. The landslide, which rolled over the glacier, is not very noticeable to the thousands of cruise ship passengers who visit Glacier Bay National Park near Juneau each summer. That is because it is about 12 to 15 miles up the glacier from the bay. 
Lituya Mountain has been the scene of extraordinary geophysical events before. In 1958, a landslide on the other side of the mountain produced a wave estimated at 1,700 feet.
One fishing vessel was able to ride out the wave.
"They looked below them and they could see the tops of the Sitka spruce trees way below them.," Geertsema said.
Another boat with two people aboard disappeared.
One of Olson's photos of the June landslide shows a huge dent in the side of an ice-covered peak. Another shows a river of rock and ice that flowed out of a valley. The landslide triggered numerous avalanches.
Glacier Bay National Park Superintendent Susan Boudreau said visitors to the 3.2 million-acre park won't notice anything different in the landscape this summer but the rock and ice likened to a river of black syrup moving toward the bay is on the move. How fast it is moving is still the question, she said.
"It is going to come down but we don't know the speed of that," Boudreau said.
Several factors contribute to the likelihood of mountains collapsing, Geertsema said. Sometimes it is caused by a general weakening of the rock. Other times it could be due to a very large snowpack that melts quickly.
Scientists also are looking at the role of climate change.
"We are seeing an increase in rock slides in mountain areas throughout the world because of permafrost degradation," Geertsema said.
Permafrost is ground that stays perpetually frozen.
Geertsema said Swiss scientists are becoming increasingly convinced that climate change is playing a role in the frequency of rock slides, after they look at data from instruments measuring temperature and the widening and narrowing of gaps in the rocks in the Alps.
"It plays an important role," Geertsema said of climate change. "I think we have been underestimating the role it might play."
Park ecologist Lewis Sharman said the landslide is a reminder of why Glacier Bay National Park is special.
"These types of events to me are welcome reminders that this place is one of the coolest on earth," he said.
The Alaska Progressive Review decided to consult an expert opinion about this massive slide. Dr. Hig Higman, consulting geologist, and co-counder of http://www.groundtruthtrekking.org/ ground truth trekking, gave us his opinion today:
"...emailed some folks at the USGS to see if they were going to survey. I think it would be well-justified, given the risk such landslides pose when they might hit water and generate tsunamis. Other than the well-known example in Lituya Bay, there was a similar landslide tsunami in Grewingk Lake in 1967. Glacier Bay, Columbia Bay, and Northwestern Lagoon (among others) all attract boats packed with tourists and have recently deglaciated slopes that could produce landslides into the water. This type of tsunami is sharp enough it poses a greater danger to ships (larger accelerations, higher chance of breaking, and for very large ships it might even have the potential to bridge the ship and cause its internal structure to fail.)
"Permafrost melting is likely not a causal mechanism here. These mountains are deforming quite actively, and unstable... these things happen sometimes, and are the main way that the upper reaches of the mountains are eroded. However, deglaciation increases the probability of this sort of event because the confining pressure of the glacier provides a stabilizing force... when it's removed shear stresses increase and failure is more likely."
Dr. Higman has many years of experience as a consulting geologist, and in working and traveling through the back-country of Alaska, so he understands how geological and climatic forcing affects our extreme landscapes here.
As a reminder of just how harsh of an environment it is in the 2000-5490 metre coastal ranges that ring half of the Gulf of Alaska, we have a few pictures from our trip last October on the Pacific side, of last month's Mt. Lituya slide.
While on the Gulf of Alaska side of these coastal mountains there is a 2-20 km wide margin of low-elevation forested land (sitka spruce mainly-high latitude rain forest) with soil, on the other side, dropping down into the Yukon, British Columbia, and Glacier Bay, it's all just sheer rock and ice. As you can see from this view looking at the western, moister, milder side on the Gulf of Alaska coastline, these mountains rise abruptly from the narrow coastal plain 2000 to 5000+ metres! At these elevations, annual snowfalls (above 3000 metres rainfall only ever occurs briefly in summer, snowfall is continuous throughout the year) of 20 metres or more occurs! Thus incredible loadings of heavy wet snow occur on these precipitous slopes. Mountaineering here is treacherous because of the great danger of massive avalanches and icefalls. Just look at that terrain, and that's not even Mt. St. Elias.
Here is a picture of 5489 metre Mt. St. Elias, from my visit to its foregrounds on the Malaspina glacier front last October. Look at how steep those slopes are, and how thick the snow and ice cover is. Think about how difficult trekking would be over these areas, not just with expedition survival equipment, but with scientific equipment as well. Rock and icefalls, combined with constant avalanche potential because of the constant parade of low pressure systems/fronts, would require expert mountaineering skilled/experienced people to be able to access the Mt. Lituya slide area on foot, with limited or no areal operations support.
Regardless of the cause of this event, whether it was made more likely or not because of the rapid warming that has occurred over the past 60 years in Alaska, http://akprogressive.blogspot.com/2011/05/fahrenheit-2051.html
we fully agree with Hig, that detailed surveying of this event should be a high priority, so we can understand its mechanisms, and determine if other areas of the state, which see more visitors, could be at risk of such events in the future. Cheers.
