I find it fascinating that these large geological events go unnoticed since it's in such remote locations. On Christmas eve there was a large landslide on the Canadian side of the Taku river (a mountain side fell into the river) and nearly blocked the rivers path. Im not certain if the FB post will show but the direct link should take you to it.

I can't find any mention of this event from a reputable source, however there does appear to be anomalies that indicate something happens when looking st the USGS seismic events and the Taku river data.

https://m.facebook.com/story.php?story_fbid=10157308041127434&id=516837433&sfnsn=mo

https://earthquake.usgs.gov/earthquakes/eventpage/us6000d2p1/executive

https://waterdata.usgs.gov/ak/nwis/uv?cb_00010=on&cb_00036=on&cb_00065=on&cb_00300=on&cb_00400=on&cb_32295=on&cb_32322=on&cb_63680=on&cb_70969=on&format=gif_default&site_no=15041200&period=&begin_date=2020-12-22&end_date=2020-12-29

"This appears to be a large rock slope failure, with a substantial mass perhaps detaching from high on the slope. If so, this mass has then triggered the failure of face of the slope below. The mass was in free-fall for a considerable distance on impact with the valley floor it has instantaneously fragmented to create an avalanche with a long run out and considerable dispersion. There is also a large volume of scree at the foot of the slope, suggesting multiple smaller failures after the main collapse.

The videos also seem to show that the landslide deposit has lobate structures at the margins, which seem to form during late stage sliding across frozen surfaces, and hummocky mounds within the landslide mass.
Hig pointed out to me that the Facebook postings give some indication of the timing of the event. On 24 December 2020 at 19:50 UTC a M=2.9 earthquake was recorded very close to this location. It is very likely that this is the record of the landslide itself the magnitude is about right for a rock slope failure of this scale, and of course a free-falling mass is going to have generated a really substantial release of energy.

At this time of year it is very difficult to obtain satellite imagery of this area, and of course the deposit may become covered by snow. This is another site that we will probably need to wait until the Spring before we can obtain a better understanding."

The scale is crazy!

Wonder if this will effectively create a smallish lake or if the river will divert easily around. The scale of it is tremendous.

Thats cool.

AgBQ-00 said:

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Wonder if this will effectively create a smallish lake or if the river will divert easily around. The scale of it is tremendous.

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My wife and I were discussing the same thing. This is very very cool.

BSD said:

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AgBQ-00 said:

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Wonder if this will effectively create a smallish lake or if the river will divert easily around. The scale of it is tremendous.

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My wife and I were discussing the same thing. This is very very cool.

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prob won't know the full extend until things thaw out many months from now.

This is definitely cool. For those that haven't heard about the1959 Hebgen Lake earthquake, below is a link to the Wikipedia page. The earthquake and resulting landslide created Quake Lake. It's also interesting to read about the seiche wave that formed in the lake and its effect on Hebgen Lake.

https://en.m.wikipedia.org/wiki/1959_Hebgen_Lake_earthquake

There was another mountain landslide in 1958 that was the result of an earthquake at Lituya Bay that resulted in an unfathomable mega tsunami. Big things happen here in AK.

"The 1958 Lituya Bay earthquake occurred at July 9 at 22:15:58 with a moment magnitude of 7.8 and a maximum Mercalli intensity of XI (Extreme). The strike-slip earthquake took place on the Fairweather Fault and triggered a rockslide of 40 million cubic yards (30 million cubic meters and about 90 million tons) into the narrow inlet of Lituya Bay, Alaska. The impact was heard 50 miles (80 km) away,[6] and the sudden displacement of water resulted in a megatsunami that washed out trees to a maximum elevation of 1,720 feet (524 meters) at the entrance of Gilbert Inlet.[7] This is the largest and most significant megatsunami in modern times; it forced a re-evaluation of large-wave events and the recognition of impact events, rockfalls, and landslides as causes of very large waves."

https://en.m.wikipedia.org/wiki/1958_Lituya_Bay,_Alaska_earthquake_and_megatsunami

If you think these things are super rare, there's concern it may happen more often as glaciers retreat and no longer help to "hold up" mountains with the static pressure they exert on their sides. Only 5 years ago there was another landslide tsunami in Icy Bay that was massive in comparison to other famous tsunamis that are viewable on YouTube. Expect ot happened in October and no one was around the area so it went unnoticed for 8 months.

"The impact of the slide with the water generated one of the tallest tsunami waves in historical times. At one location, the wave reached 633 feet (193 m) above sea level. As it moved down the fjord, the wave stripped vegetation to varying heights that gradually diminished down-fjord. At the mouth of the fjord, 10 miles (16 km) from the landslide, the wave reached 50 feet (15 m), and dragged icebergs through moraine hills. Two-and-one-half-miles (4 km) farther, on a section of the west coast of Icy Bay that faces directly toward the mouth of Taan Fiord, the wave reached 36 feet (11 m) and toppled trees, but quickly diminished to below high tide as it spread out along the coast (Figure 2). The faint echo of the tsunami reached tide gages 80 and 250 miles (130 and 400 km) away where they recorded 40-minute-long oscillations of several inches in water level."

https://www.nps.gov/articles/aps-18-1-2.htm

Now for scale, compare that potential destructive force to that of something like the 2011 Japan tsunami that only reached a max height of 114ft.