March 21, 1825 Tsunami: Unimak Island, AK, United States

1825, March 21 (Gregorian date). A powerful eruption of Shishaldin Volcano on Unimak Island began at the end of 1824 with the sound of explosions being heard from the Alaska Peninsula to Unalaska. The ashes and water mixed with rubble inundated the southern coast of the island for a distance of 2 miles. The report that the sea was agitated six months later, and the lack of reports of waves at the time of the main eruption, casts doubt on this as a report of a tsunami. This account in Soloviev and Go (1975) that was taken from Perry (1865) forty years later is in error regarding the data. Veniaminov (1984, p. 18) reports:

"On March 10, 1825 [Julian date] after a loud subterranean thunder very similar to a cannonade, which lasted almost the whole day and was audible on Unalaska, Akum, and the tip of Aliaksa [the Alaska Peninsula] in the middle of the day, the northeast range of Unimak exploded in five or more places and over a large area with an eruption of flames and a great quantity of black ash which covered the whole end of Aliaksa for several inches. At nearby Aliaksa and especially Morzhevskoi settlement, it was dark for 3 or 4 hours. On this occasion the ice and snow lying on the range melted and for several days flowed in a dreadful river, 5 to 10 verst wide [3.3 to 6.6 miles; a verst is 0.6624 miles]. These waters poured over the eastern side of the island in such a quantity that the nearby sea remained muddy until late autumn."

This second account by Veniaminov (who began serving this area shortly after this event) seems to account for the six month agitation of the sea, and fixes a date. The 3.3 mile width may account for the distance of inundation reported by Soloviev but this was a lahar, or mud flow from melting ice and snow on the volcano. It does not mention anything that could be considered a tsunami report. Validity 0.

(Above from reference #239)

A powerful eruption of the Shishaldin volcano on Unimak Island began at the end of 1824. In the middle of March 1825, the sound of underground explosions was heard from Unalaska Island to the Alaska Peninsula. the volcano disgorged flames, ashes and streams of water, mixed with rubble, which inundated the southern coast of the island for 4 km (2 miles). The outpouring did not last long, but the sea was still agitated even in the following fall (Reference #414).