Thursday, 26 March 2020

Into Lituya - Site of the Megatsunami and La Perouse's Lost Crew




As a child I read, in National Geographic I suspect, about the 1958 megatsunami in Lituya Bay and sure enough when I did the initial planning for our Alaska adventure there it was pretty much on our rhumb line. The megatsunami was one of the biggest waves ever recorded ...  a 1,720 ft wave ... Obviously we needed to stop there ...

We anchored in Lituya Bay after short overnight passage from Yakutat. We had great mountain views on the passage including Mt St Elias (18,008 ft) and Mt Fairweather (15,300 ft) lit by sunlight and then the northern lights. At first we anchored just inside the bay near where La Perouse (a French explorer following a few years after Capt Cook's last voyage) lost over 10% of his crew when their long boat was swept out of the pass on the ebb tide in 1786.  Despite this history, it was an amazingly beautiful spot and even after a brief nap to recover from the overnight passage it was tempting to linger.  However, we moved up the fjord to see the effects of the 1958 tsunami.

Anchored at the mouth of Lituya Bay. It was so tempting to stay longer with views like this.
As we approached northeast end of the fjord where the Gilbert and Crillion Inlets were supposed to be, we had a surprise.  Both inlets had disappeared, and there were mud flats about 7 ft above chart datum 1.3 nm out from where the beach was supposed to be.  Crillion Glacier was about 0.9 nm further towards the sea than the charts show (we have Navionics and NOAA charts).   This was especially impressive as Crillon Inlet was shown to be 380 feet deep on the chart.

The blue arrows roughly correspond to the same location.  The Navionics chart and reality rather do not match.

And here is the view using the latest NOAA raster charts showing about 70 fathoms of water where we anchored. We anchored in about 17 fathoms and the shore line was over a mile closer than indicated

and using the latest NOAA vector charts it is about the same - approx 400' of water expected.  We anchored in about 100' and the shore line was over a mile closer than indicated
We anchored Fluenta in 100' (should be about 400' according to the chart) very close to the shore (not an overnight anchorage !) and the kids and I did a minor expedition ashore to walk to the glacier face.  We saw lots of bear and potentially wolf prints so kept the shore excursion short.

Liz looking more cheerful than I think she was feeling about anchoring here.

You can see there is not a lot of swinging room.  Note we did not stay overnight and we left Liz onboard to monitor the situation while the kids and I went ashore.
the cool patterns where the glacier outflow mixed with the fjord water.

The shore party heading to the beach.

Checking out the bear tracks.  We did a quick hike to the terminal moraine in the distance.  The teenagers took the first photo in this blogpost from the top of the moraine.
Yet another location where we would be happy to spend lots more time but alas the season was moving along and we had a weather window to continue south to join the masses in SE Alaska.

The Google Earth view of where we anchored.  Note the shore line has moved closer to the centre than even what is in the Google data.

A schematic showing how the tsunami occurred. (from Wikipedia)
A photo from 1958 showing where the landslide started from (the red arrow) and then where the largest wave was located (yellow arrow) (From Wikipedia)

As seen from Fluenta, the difference in the vegetation is still apparent.
And for folks looking to follow in our path, a copy of our tracks are below:

Yakutat to Lituya


We anchored in both the western and north eastern ends of the fjord although only for short stops.  I have read reports of yachts waiting out bad weather in the western anchorage.




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