Aniakchak (United States): Recorded Eruptions and Historical Activity

Aniakchak is a caldera volcano located in the United States at a tectonic setting characterized by a subduction zone and continental crust exceeding 25 kilometers in thickness. Standing at an elevation of 1,341 meters, the volcano has a recorded history spanning 16 confirmed eruptions stretching from deep antiquity into the 20th century CE.

According to the Smithsonian Global Volcanism Program records, the earliest recorded eruption for Aniakchak dates back to approximately 6300 BCE, carrying a Volcanic Explosivity Index (VEI) of 6.0 and an estimated start year uncertainty of 1,250 years, determined via tephrochronology correlation. The most recent confirmed eruption in the official record began on May 1, 1931, and ended on June 13, 1931, with activity noted on the west and southwest caldera floor and a recorded VEI of 4.0.

Recorded Eruption History and Chronology

The 16 confirmed eruptions recorded for Aniakchak are distributed across multiple centuries and millennia BCE and CE. The official record documents five eruptions with assigned Volcanic Explosivity Index (VEI) values, reaching a largest recorded VEI of 6.0. These large-scale events include eruptions dated to around 6300 BCE and 1645 BCE (the latter determined through sidereal ice core evidence with a start year uncertainty of 10 years).

Other documented events rely on various evidence methods, such as calibrated radiocarbon isotopes for the 370 BCE eruption (with an uncertainty of 210 years) and tephrochronology correlation for an eruption in 1050 CE centered around Vent Mountain and other vents. Across the entire collection of 16 confirmed eruptions, individual events are distributed across centuries ranging from the 63rd century BCE up to the 20th century CE.