Kuchinoerabujima (Japan): Recorded Eruptions and Historical Activity

Kuchinoerabujima is a stratovolcano located in Japan at a tectonic subduction zone in oceanic crust less than 15 kilometers deep. Standing at an elevation of 657 meters, the volcano has a rich historical and prehistorical eruption record maintained by the Smithsonian Global Volcanism Program. The official record documents 29 confirmed eruptions, stretching from early radiocarbon-dated activity in the 10th millennium BCE through modern reported events up to 2020 CE.

Chronology of Recorded Eruptions

The historical and geological record for Kuchinoerabujima spans multiple centuries and millennia, combining isotopic dating methods for ancient events with direct human observation for modern activity. Out of the 29 confirmed eruptions in the database, 18 include recorded Volcanic Explosivity Index (VEI) values, reaching a maximum recorded VEI of 4.0.

Ancient activity is documented via calibrated 14C isotopic evidence. For example, an early confirmed eruption at the Furudake activity area is dated to 9520 BCE with an estimated start-year uncertainty of 300 years. Subsequent pre-modern and medieval activity includes confirmed events such as an eruption around 1110 CE (with a 75-year uncertainty) at the Furudake area.

In the 20th century, activity shifted toward observed and reported events, frequently localized around Shindake and its southwest flank. Notable recorded sequences include:

• April 2 to June 22, 1931: An eruption on the southwest flank of Shindake with a recorded VEI of 3.0, documented via reported observations.
• December 23, 1933 to January 12, 1934: A larger eruption at Shindake reaching a VEI of 4.0, which stands as the largest recorded VEI for the volcano.
• August 29, 2020: A confirmed eruption at Shindake with a VEI of 1.0, representing the latest recorded eruption in the official dataset.

Distribution of Eruptive Activity by Century

The confirmed eruptions span various centuries across millennia, reflecting periods of both frequent documentation and sparse ancient data. The distribution across recorded centuries illustrates how eruption frequency appears denser in modern periods primarily due to observation capabilities:

• 96th century BCE: 1 eruption
• 35th century BCE: 1 eruption
• 15th century BCE: 1 eruption
• 12th century BCE: 1 eruption
• 6th century CE: 1 eruption
• 10th century CE: 1 eruption
• 11th century CE: 1 eruption
• 12th century CE: 1 eruption
• 15th century CE: 2 eruptions
• 16th century CE: 1 eruption
• 19th century CE: 2 eruptions
• 20th century CE: 11 eruptions
• 21st century CE: 5 eruptions

The evidence demonstrates that Kuchinoerabujima has experienced recurring episodes of unrest and explosive activity across different vents, primarily centered around the Furudake and Shindake structures.