Kusatsu-Shiranesan (Japan): Recorded Eruptions and Historical Activity

Kusatsu-Shiranesan is a stratovolcano located in Japan at an elevation of 2,165 meters, sitting within a tectonic setting characterized by a subduction zone and continental crust greater than 25 kilometers thick. According to the Smithsonian Global Volcanism Program, the volcano has a total of 28 confirmed eruptions spanning from prehistoric dates through the 21st century CE.

Eruption History and Chronology

The historical record for Kusatsu-Shiranesan includes activity distributed across multiple centuries, ranging from early radiocarbon-dated events to direct historical observations. The earliest recorded eruption in the dataset dates back to 6550 BCE at the Shirane activity area with a Volcanic Explosivity Index (VEI) of 3.0. Later prehistoric activity includes a VEI 4.0 eruption at Moto-Shirane around 1120 BCE, carrying an uncertainty of 150 years.

Directly observed historical eruptions began to be documented in later centuries, such as a VEI 2.0 eruption at the Yu-gama activity area starting on July 2, 1805. In the 20th century, multiple eruptions were documented, including an event spanning from December 29 to December 31, 1927, which occurred at the north Yu-gama and south outer rim.

Recent Activity

The most recent confirmed eruption in the official record occurred at Motoshiranesan on January 23, 2018, registering a VEI of 1.0. Across the entire catalog of 28 confirmed events, the largest recorded Volcanic Explosivity Index is 4.0, with 26 eruptions containing explicit VEI observations.