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Old 06-05-2020, 08:42 AM   #1
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Thinking about going to Prince William Sound?

Check out this warning.
http://dnr.alaska.gov/commis/pic/rel...ists%20say.pdf
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Old 06-05-2020, 08:52 AM   #2
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Wonder if they couldn't blast it, like they do to trigger avalanches?
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Old 06-05-2020, 10:11 AM   #3
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Greetings,
Mr. BD. Indeed troubling. I certainly would NOT go anywhere near the area if I was boating in Alaska. Might even have an effect on the whole Gulf of Alaska to varying degrees.
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Old 06-05-2020, 10:38 AM   #4
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This area has a history of big earthquakes and tsunami's. Lituya Bay, ~300 miles to the SE on the Gulf of Alaska had the biggest tsunami ever recorded in 1958, caused by the collapse of a rock face after an earthquake.

https://en.wikipedia.org/wiki/1958_L...nd_megatsunami
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Old 06-05-2020, 12:01 PM   #5
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PWS is our favorite place in the world. ASD has yet to cruise that far north, but we would fish PWS in our riverboat every weekend.
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Old 06-05-2020, 12:14 PM   #6
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We are in Prince William Sound every time we leave port.

It is a HUGE place. Think of Puget sound and then take away the people. That is Prince William Sound.

The landslide threat is very real. We are staying away from that part of the sound. We are frequenting an area probably 50 miles away. No risk for us.

Folks that boat our of Whittier are at risk though. They leave passage canal and Port wells is on the north, which is the area at risk.
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Old 06-05-2020, 12:26 PM   #7
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Main Bay our favorite "Snagging" place...
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Old 06-06-2020, 09:57 AM   #8
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Kevin,
I don't know the area, but if there have been landslide caused mega tsunami's in the past (one recorded water making it 1700 feet vertical up the opposing forested face from a distance of 1.3 km), could that possibly affect other areas nearby? Fifty miles doesn't sound like it is far enough away (??) for something like that! Be safe.
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Old 06-06-2020, 10:07 AM   #9
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I certainly would NOT go anywhere near the area if I was boating in Alaska.
Neither would I!
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Old 06-06-2020, 11:00 AM   #10
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Kevin,
I don't know the area, but if there have been landslide caused mega tsunami's in the past (one recorded water making it 1700 feet vertical up the opposing forested face from a distance of 1.3 km), could that possibly affect other areas nearby? Fifty miles doesn't sound like it is far enough away (??) for something like that! Be safe.
The effect of a landslide caused tsunami is localized especially when it’s in a enclosed bay as this potential one is.

Earthquake cause tsunami’s move much more water, but with much less initial heigh than landslide based tsunami’s because the earthquake movement is spread out over a wide area along a fault line.

Landslide caused tsunami’s seem to move much less volume, but when that volume is all in a enclosed bay the local terrain such as a bay the immediate effect can be tremendous.


Drop a rock in a bowl of water (simulating a enclosed bay) and think of the height.

Now drop that same rock in a swimming pool or at the harbor and the differences become easier to think about.
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Old 06-06-2020, 11:30 AM   #11
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Yikes...is it recently exposed lateral moraine material? That stuff is unstable for sure.

The whole BC and SE Alaska coast along the mainland inlets is pretty active, geologically speaking, being such a young mountain range.

A modern survey was done of Douglas Channel because of a proposed industrial development, and two massive marine landslides were discovered near a previously unknown earthquake fault line:

Quote:
"Submarine slope failures and tsunami hazards in coast British Columbia: Douglas Channel and Kitimat Arm." It says the scientists discovered "evidence of large submarine slope failures in southern Douglas Channel."

The research identified two slides, one estimated at 32 million cubic metres and a second of 31 million cubic metres. The report goes on to say that the discovery of an "apparently active fault presents the possibility that they may have been triggered by ground motion or surface rupture of the fault during past earthquake events."

What's worrying about the discovery is the fact that there were two recent submarine slope failures near Kitimat on Douglas Channel. The first slope failure occurred on Oct. 17, 1974, triggering a 2.4-metre tsunami at low tide. Then on April 27, 1975 there was a second slope failure near low tide on the northeast slope of the Kitimat Arm that generated an 8.2-metre tsunami. The 1975 tsunami destroyed the Northland Navigation dock near Kitimat and damaged the Haisla First Nation docks at Kitamaat Village.
https://www.huffingtonpost.ca/robin-...b_1894385.html

There have also been a lot of landslides associated with logging on steep slopes in our area. None of the trees along the shoreline on the opposite sides of the bays were taken out, but any boat anchored would have had a nasty surprise! Avalanches would also reach quite a ways into a bay as well. So many things to ponder while choosing where to anchor.
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