Each evening between May and October, colorful pyrotechnics illuminate the skies over Lake Toya, as hundreds of fireworks are set off from boats on the still waters. The spectacular event attracts hundreds of thousands of visitors annually to the scenic lake, which lends its name to the surrounding Shikotsu-Toya National Park on Japan’s northernmost main island, Hokkaido.
Yet at numerous points in history, a different kind of fireworks have reflected off Lake Toya. Indeed, a volcanic eruption some 110 million years ago created the caldera lake, which views from outer space show to have a near perfectly circular shape. Toya’s glassy surface mirrors nearby Mount Uso, which regularly spouts spirals of smoke as evidence of the seismic activity still taking place underground. The 2,400-foot-high stratovolcano, one of Japan’s most active, erupts regularly at around 30-year intervals; Uso’s most recent eruption in 2000 caused the evacuation of some 16,000 residents and more than $100 million in damages. The small Volcano Science Museum shows fascinating footage of the 1977 and 2000 eruptions.
When another volcano, Mount Yosomi-yama, blew in 1910, it triggered similar disruption on the earth’s surface, but with much more satisfying results. Newly discovered hot springs poured along stretches of Lake Toya; the resulting Toyako Onsen is lauded as one of Hokkaido’s best spa resorts. The Yosomi-yama Trail, a 45-minute loop encircling the thermal area that formed during the 1910 eruption, reveals still vaporous fumaroles amidst the new-growth forest.
Lake Toya’s active volcanism—along with its diverse landscapes and rich flora and fauna—drew world leaders to its shores for the G8 Hokkaido Toyako Summit in 2008. Two years later, UNESCO designated the Toya-Usu region as a Global Geopark. The lake, which never ices over, is a popular year-round destination for Japanese residents, who make the day-trip from Sapporo to soak in its mineral pools, fish for trout and smelt, and admire the dramatic change of seasons. Yet it is the summer fireworks display that reminds visitors nightly of the region’s explosive power.