Volcano Type: Stratovolcano
Volcano Status: Radiocarbon
Last Known Eruption: 1900 BC ± 150 years
Summit Elevation: 1032 m 3,386 feet
Latitude: 56.552°N 56°33’9″N
Longitude: 158.785°W 158°47’5″W
Black Peak
The highly eroded stratovolcano and lava dome complex of Black Peak was constructed within an ice-free mid-Holocene caldera with two small caldera lakes on the northern and eastern sides. The pre-caldera volcano consists of andesitic-dacitic lava domes, lava flows, and volcaniclastic rocks that were constructed over a basement of Pliocene volcanogenic sedimentary rocks. Ash-flow tuffs and block-and-ash-flow deposits from the >10 cu km caldera-forming eruption, which occurred less than about 4000 years ago, fill the Ash Creek and Bluff Creek valleys to the west and north to depths of as much as 100 m. Most of the 3.5-km-wide caldera floor is occupied by a complex of nested dacitic lava domes and associated lava flows centered in the southern part of the caldera.
Black Peak Volcano is located 45 km south of Port Heiden, Alaska. The volcano contains a 3.5 km wide caldera with 2 small lakes. Eruptions have produced lava domes and lava flows. A caldera forming eruption years ago erupted 10-50 cubic km of material. The caldera is the smallest of three neighbouring calderas. On the west side of the volcano are two 100 m thick ash flow tuffs.
Black Peak
Black Peak is a deeply eroded, highly altered stratovolcano/dome complex with a small caldera at its eastern edge. The caldera is ice-free and contains two small lakes; most of the interior of the caldera is occupied by a complex of nested dacitic domes. The volcano rests on a north-dipping basement of Pliocene volcanogenic non-marine sedimentary rocks. The flows, domes, and volcaniclastic rocks that make up the pre-caldera cone range in composition from andesite to dacite. Dacitic ash-flow tuffs and coarse block-and-ash flows fill the Bluff and Ash Creek valleys to as much as 100 m on the north and west sides of the volcano. The pyroclastic flows that deposited these tuffs had limited distribution and appear to have been relatively sluggish; they also appear to have had a large air-fall component, judging from the crude stratification in the ash-flow tuff. In spite of the caldera’s small diameter, the widespread climactic air fall and the thickness of the ash-flow tuffs suggest a bulk eruption volume of >10 cubic km.
Originally posted 2010-09-03 11:46:53.
