USAF pilot Jerry Nelson observed renewed activity from Gareloi during an overflight on 17 September. As he approached the volcano at about 1600, he saw a slight wisp of vapor that grew rapidly into a dark brown ash-rich column reaching about 6 km altitude. The eruption column, which appeared to originate from the E side of the summit crater, drifted slightly N or NW. The activity was visible until Nelson left the area about 10 minutes later.

Geological Summary. The 8 x 10 km Gareloi Island, the northernmost volcano of the Delarof Group at the western end of the Andreanof Islands, consists of a stratovolcano with two summits and a prominent SE-trending fissure. The fissure was formed during an eruption in 1929 and extends from the southern summit to the sea. Steep sea cliffs that are cut into rocks of an older, eroded center are found on the SW coast, and submarine deposits of three debris avalanches produced by edifice collapse are found offshore. Young lava flows cover the older volcano from the summit to the coast along three broad axes trending NW, ENE, and S. The 1929 eruption originated from 13 craters along a 4-km-long fissure. Phreatic explosions were followed by the ejection of glassy pumice, lapilli, scoria, and older blocks, as well as by the emission of four short, steep lava flows, one of which reached the SE coast.

Information Contacts: T. Miller, USGS, Anchorage AK; J. Nelson, U.S. Air Force, Travis AFB, CA.