Ugashik and Peulik
Location: 57.70N, 156.35W
Elevation: 1709 ft (521 m)
Ugashik is a caldera of Ugashik-Peulik. It is ~3 miles (5 km) wide. This caldera is what remains of an old stratovolcano. It is ~980 ft (300 m) high. The diameter of the caldera is ~3.5-5 miles (6-8 km). Ugashik is composed mainly of dacite and rhyolite. Only a few hundred meters of dacite flows and volcaniclastic rocks can be found high on the caldera rim. At least five non glaciated domes of dacite to rhyolite composition can be found inside the caldera. Ash flow tuffs from the eruption that formed the caldera have not been found outside the caldera. Pumice fragments, however, have been found in surface deposits around the volcano.
Location: 57.75N, 156.35W
Elevation: 4835 ft (1474 m)
Peulik is a stratovolcano. It is ~2130 ft (650 m) high. The diameter of this volcano is 33.2 miles (53.5 km). It is composed mostly of basalt and dacite. A small parasitic stratovolcano is located 1.5 miles (2.5 km) north of Peulik. Flows from the summit of Peulik have breached the north rim of the caldera. Basaltic flows from flank eruptions cover 8 sq km north of the volcano. The summit crater is breached to the west. It contains a large dacite dome. A smaller dome is located high on the east side of the cone. Block and ash flow deposits resulting from summit dome building activity cover a 40 sq km area west of the cone. Avalanche deposits underlie an area of 75 sq km northwest of the volcano.
Sources of Information:
Wood, Charles A. and Kienle Jurgen, "Volcanoes of North America," Cambridge University Press, New York, 354 pp., 1990.