Aira is a caldera volcano located in Japan at a tectonic subduction zone in continental crust more than 25 km thick. Standing at an elevation of 1,117 meters, the volcano features a confirmed record of 48 eruptions spanning thousands of years, with activity ranging from prehistoric events dated through isotopic methods to historical eruptions documented by human observation.
According to the Smithsonian Global Volcanism Program's official records, the earliest recorded eruption took place around 8050 BCE at the Wakamiko Caldera, carrying an estimated Volcanic Explosivity Index (VEI) of 6.0 and an uncertainty of 1,000 years. Throughout its long history, Aira's activity levels have varied significantly across centuries, encompassing both lower-magnitude events and larger explosive occurrences.
Historical Eruption Record and Chronology
The documented eruption record combines ancient isotopic data with centuries of human observations. For example, an eruption was reported in 0708 CE with a VEI of 3.0. Later centuries, particularly the 18th and 20th centuries, account for a substantial portion of the recorded events, taking place across areas such as the Minami-dake summit and surrounding flanks with varying explosive magnitudes.
Representative milestones in Aira's documented activity include:
- 8050 BCE: A prehistoric eruption at the Wakamiko Caldera with a VEI of 6.0 (uncertainty of 1,000 years).
- 0708 CE: A confirmed eruption documented through reports, registering a VEI of 3.0.
- September 1749: An eruption recorded at the Minami-dake summit and west flank with a VEI of 2.0.
- July 2, 1860: An observed eruption at Minami-dake with a VEI of 1.0.
- March 25, 2017: An eruption beginning at the Minamidake summit crater with a VEI of 2.0.
Understanding the Volcanic Explosivity Index (VEI)
The Volcanic Explosivity Index (VEI) is a relative scale used to describe the size of explosive volcanic eruptions based on factors such as volume of products ejected and eruption cloud height. At Aira, recorded VEI values span from lower-magnitude events (VEI 1.0) up to large-scale explosive events reaching a VEI of 6.0. Out of the 48 total confirmed eruptions in the official database, 40 include a recorded VEI observation.
Frequently asked questions
How many confirmed eruptions does Aira have?
The official record from the Smithsonian Global Volcanism Program lists 48 confirmed eruptions for Aira.
When did the earliest recorded eruption at Aira occur?
The earliest recorded eruption occurred around 8050 BCE at the Wakamiko Caldera, with an estimated year uncertainty of 1,000 years.
What is the highest VEI recorded for Aira?
The largest recorded Volcanic Explosivity Index (VEI) for Aira is 6.0.
Where is the Aira volcano located?
Aira is located in Japan at a tectonic subduction zone, with an elevation of 1,117 meters.
Image credits
- Jeff Schmaltz, MODIS Land Rapid Response Team, NASA GSFC — Wikimedia Commons source — Public domain
Sources and further context
Official datasets support the event-specific facts.