Shikotsu

Lake Shikotsu, filling the caldera, is Japan's second-deepest lake at 360 m and remains ice-free throughout Hokkaido's harsh winters.

Tarumaesan has produced four VEI 5 eruptions — at ~6950 BCE, ~550 BCE, 1667, and 1739 — making it one of Japan's most explosively powerful volcanoes.

The caldera-forming eruption 31,000–34,000 years ago was one of the largest Quaternary volcanic events in Hokkaido.

Tarumaesan's distinctive flat-topped lava dome, formed in 1909, is a beloved Hokkaido landmark visible from Sapporo, 40 km away.

New Chitose Airport, Japan's third-busiest airport, lies only 20 km east of the caldera — well within ashfall range of a major eruption.

Pyroclastic-flow deposits from the 1667 eruption extend nearly to the Pacific coast, covering a distance of approximately 25 km.

The name Shikotsu comes from the Ainu language, meaning 'large depression' or 'large lake.'

Three post-caldera volcanoes — Tarumaesan, Fuppushidake, and Eniwadake — are aligned along a NW-SE structural trend within the caldera.

The 1667 and 1739 VEI 5 eruptions occurred only 72 years apart, demonstrating that paired catastrophic events are possible.

Sapporo, Japan's fifth-largest city with approximately 2 million residents, lies within the potential ashfall zone of a major Tarumaesan eruption.