Alaska, United States
Mount Trident, officially known as Trident Volcano,
is an eroded volcanic complex consisting of numerous domes (up to 23), as high as 6115 feet in elevation, along a northeast-southwest oriented volcanic front on the Pacific Ocean side of the Alaska Peninsula. A new dome was emplaced beginning in 1953 at an altitude of 3599 feet in an amphitheater on the southwest flank of the southwest peak.
Historical volcanic activity
There is no evidence of recent eruptive activity at the summit of Trident, nor have there been any reports of historical activity, except fumarolic activity on the east side. The earliest known activity were minor eruptions in 1913, 1949 and 1950. A satellite cone formed February 15, 1953 on the southwest flank of Mount Trident following a major explosive eruption that sent ash to an altitude of over 5.6 miles. A succession of blocky lava flows were erupted in 1954, 1957, 1958, 1959-1960 from the new vent. Ash eruptions, some to altitudes over 7.5 miles, were associated with several of the lava eruptions. By 1960, the dome had grown nearly 853 feet high and a sequence of viscous flows, up to 984 feet thick and covering an area of about 1200 acres south of the volcano, had been extruded. Further explosions were reported in the early to late 1960s. Lava extrusion, accompanied by explosions were also reported from 1966 to 1968 and 1974 to 1975. In 1983, steam and/or vapor continued to rise from the central vent area of the new cone as well as from numerous fumaroles on the near-vent portion of the blocky lava flows.
Trident lavas are andesitic to dacitic in composition. The dominant phenocrysts are zoned plagioclase, hypersthene, calcic clinopyroxene, titanomagnetite, and rimmed olivine. The five flows which erupted from the new vent during the period from 1953 to 1963 are olivine-bearing, two pyroxene, high-silica andesite.