Hi Cheryl, The problem with the lake is there does not appear to be any shore erosion from waves. Also there the inflow is not represented by a channel, and the outflow is not directly to the ocean. Some sort of an earth pipe.?? Also, the color is wrong for water, unless it's mostly some sort of growth. It dawned on me yesterday that perhaps there was some sort of a construction project during the war. The geometry does not seem to be natural. I'm going to make a few calls to the USGS, Geologic Division. I'll let you know. Best Terry On Mon, Dec 21, 2020 at 3:10 PM wrote:

Dear Terry,

I believe that feature is a lake, but to say more about it we would need to check with geologists who have been there. I am not so fortunate as to have ever visited Semi or Amchitka in person. :) You might be interested in these publications: https://pubs.er.usgs.gov/publication/sir20175150 and this one on Aleutian arc geothermal fluid: https://avo.alaska.edu/pdfs/AleutianArcGeothermal_v1.pdf

Thank you, Cheryl

Hi All, On the west side of Semisopochnoi at 51 56 43 N and 179 29 21 E there is a north- trending feature, 1135 ft x 485 ft, that resembles a lake, but probably isn't?? It appears to flow to the west into an earthen pipe?? An ancient mud flow? What is this feature? I'm a hydrogeologist and spent sometime on Amchitka for the USGS in 1967 and 68.