Mount Usu: The Volcano That Never Lies

Mount Usu (Usuzan) is not the highest volcano in Japan, nor the most beautiful. It lacks the perfect symmetry of Mount Fuji. But what it lacks in stature, it makes up for in personality and predictability. Standing on the southern rim of the vast Toya Caldera in Hokkaido, Mount Usu is a geological shapeshifter, a mountain that is constantly tearing itself down and building itself up, often right in the backyards of the people who live there.

This volcano is famous not just for its eruptions, but for the relationship between the mountain and the town of Toyako Onsen. It is a relationship defined by a unique philosophy: “living with the volcano.” Here, the volcano is not an enemy to be feared, but a neighbor to be respected—a neighbor that provides hot springs, fertile soil, and tourism, but who occasionally demands that you leave the house in a hurry.

The Volcano That Warns You

Mount Usu has erupted four times in the last 110 years: 1910, 1944-45, 1977-78, and 2000. This regularity (every 20 to 50 years) makes it one of the most active volcanoes in Japan. However, it is also known as “The Lying Volcano” (in an ironic sense) or “The Honest Volcano” because it never erupts without warning.

• Precursory Earthquakes: Every major eruption in the recorded history of Usu has been preceded by a distinct swarm of earthquakes caused by rising magma. The duration of this warning varies—from a few days to several months—but it is always there.
• The 2000 Miracle: The eruption of March 31, 2000, is a textbook example of successful disaster mitigation. On March 27, intense earthquakes began. Recognizing the signs from previous generations, scientists and local officials ordered a preemptive evacuation. More than 10,000 residents and tourists were evacuated from Toyako Onsen. When the volcano finally erupted four days later, opening new craters right near the town center, not a single person was killed or injured.

The Birth of Showa-shinzan (1943-1945)

One of the most extraordinary geological events of the 20th century happened here, in the middle of World War II.

• The Wheat Field: In 1943, a flat wheat field at the foot of Mount Usu began to tremble. The ground started to lift.
• The Growth: Over the next two years, the field rose higher and higher. A viscous lava dome broke through the surface, pushing the soil and crops upward like a roof. While the world was fighting a war, a local postmaster named Masao Mimatsu was fighting to document this miracle. He purchased the land to save it from development and created the “Mimatsu Diagram,” a series of sketches tracking the mountain’s growth.
• The Result: by 1945, the wheat field had become a 398-meter (1,306 ft) tall volcano. It was named Showa-shinzan (“New Mountain of the Showa Era”). Today, it still steams and smokes, a red, bulbous lava dome that looks like a raw wound on the green landscape. It is one of the few places on Earth where humans have witnessed the birth of a mountain from start to finish.
  • Mimatsu’s Legacy: Masao Mimatsu bought the land using his life savings, not for profit, but to protect the “new baby mountain” from sulfur mining. He became known as the “owner of a volcano.” His detailed diagrams were presented at international geological conferences and were praised for their accuracy, proving that citizen science can rival professional monitoring. A statue of Mimatsu stands at the base of the mountain, forever watching over his “child.”

The 1977 and 2000 Eruptions

Usu’s eruptions are diverse. Sometimes it builds domes; sometimes it blasts ash; sometimes it creates phreatic explosions.

• 1977-1978: This was a Plinian eruption (explosive ash release) followed by dome growth. It blanketed the lush agricultural lands of Hokkaido in thick gray ash. The eruption continued for a year, building a new peak called Usu-Shinzan inside the summit crater.
• 2000: This eruption was different. It didn’t happen at the summit. Instead, magma sought a new path, breaking through the western flank right next to the town.
  • New Craters: More than 60 new craters opened up. Steam explosions blasted rocks through roofs.
  • Faults and Deformation: The ground shifted dramatically. Roads were torn apart, and buildings were crushed not by lava, but by the ground moving beneath them. A public housing complex was notoriously raised several meters and twisted by the deformation.

Toya-Usu UNESCO Global Geopark

The area is now part of the Toya-Usu UNESCO Global Geopark, the first of its kind in Japan. The philosophy here is distinct: Preserve the disaster.

• The Ruins: Instead of cleaning up all the damage from the 2000 eruption, the town decided to preserve some destroyed structures as memorials and educational sites.
  • The Kindergarten: You can walk a trail past a kindergarten that was wrecked by rocks and ash. Inside, you can still see the children’s cubbies and toys, frozen in time (everyone evacuated safely).
  • The Damaged Road: The “Konpira Craters Strategy” walking trail takes you along a paved road that simply disappears into a crater lake, while other sections are buckled into waves of asphalt.
  • The Public Baths: The ruins of a public bathhouse sit half-submerged in mud, a stark reminder of the mudflows that followed the eruption.
  • The 1910 Craters: A short hiking trail leads to the craters formed during the Meiji era eruption. These are now peaceful, tree-lined depressions, but the ground is still warm in places. It serves as a reminder that the “peace” here is relative.
• The Volcano Science Museum: Located in the center of town, this museum is a must-visit. It houses a “volcano experience room” with a massive screen and vibrating floor that recreates the 2000 eruption. It also displays the personal stories of the residents—diaries, photos, and recorded interviews—that humanize the geological data.
• Global Network: As a UNESCO Global Geopark, Toya-Usu is part of an international network. It regularly hosts conferences where experts from volcanic regions like Iceland, Italy, and Indonesia gather to share strategies on evacuation, tourism, and education. It is a global leader in “volcano sociology.”

Tourism: Hot Springs and Ropeways

Despite the danger, Toyako is a thriving tourist destination.

• Toyako Onsen: The town is famous for its hot springs (onsen). Ironically, the 1910 eruption created the hot spring source that the town relies on. The volcano gives and the volcano takes. Every night for six months of the year, fireworks are launched over Lake Toya—not volcanic fire, but a celebration of life.
• Usuzan Ropeway: A cable car whisks visitors from the base of Showa-shinzan up to the rim of the main Usu crater.
• The Crater Rim Walk: From the upper ropeway station, a trail leads along the rim. To the right, you look down into the massive 1977 crater and the still-steaming 1978 dome. To the left, you possess a sweeping view of Lake Toya, a giant caldera lake formed by a catastrophic eruption 110,000 years ago. In the distance, the “Ezo Fuji” (Mount Yotei) rises perfectly conical against the sky.

The Future

Mount Usu is currently quiet, but it is breathing.

• Monitoring: The mountain is wired like a patient in an ICU. Seismometers, GPS stations, and cameras monitor every tremor and bulge.
• The Next One: Scientists know it will erupt again, likely within the next few decades (given the 20-50 year cycle). The town is ready. Evacuation drills are regular. Hazard maps are in every hotel room.
• Resilience: The people of Toyako have decided that the benefits of living in this beautiful, fertile, geologically active place outweigh the risks. They have learned to read the mountain’s language. When Usu speaks, they listen.

Nature’s Resurrection: Flora and Fauna

One of the most fascinating aspects of Mount Usu is the speed at which nature recovers after an eruption. The volcano does not just destroy; it resets the ecological clock.

• The Pioneer Plants: The first colonizers of the barren volcanic ash are hardy species like Japanese knotweed (Polygonum cuspidatum) and various pampas grasses. These plants have deep root systems that stabilize the loose soil and prevent erosion. They die and decompose, creating a thin layer of organic matter that paves the way for trees.
• The Succession Forest: Within a few decades, what was a grey wasteland transforms into a young forest of birch and poplar trees. These fast-growing broadleaf trees thrive in the sun-drenched volcanic soil. Visitors walking the trails near the 1977 craters can see this “succession forest” in action—a living textbook of ecology.
• Wildlife Returns: As the vegetation returns, so do the animals. The forests around Mount Usu are home to the Ezo Red Fox, the Ezo Deer, and the majestic White-tailed Eagle. The brown bear (Higuma), the symbol of Hokkaido, also roams the lower slopes, foraging for berries that grow in abundance on the acidic volcanic soil. The recovery of the ecosystem mirrors the recovery of the human community nearby—both are adapted to the cycle of destruction and rebirth.

Conclusion

Mount Usu is a masterclass in coexistence. It challenges the Western notion of “conquering” nature. Here, nature is a dominant force that cannot be tamed, only understood. The red dome of Showa-shinzan and the broken roads of the 2000 eruption serve as monuments to the Earth’s restless energy, while the bustling town next door serves as a monument to human adaptability. It is a place where destruction and creation dance a tango that has lasted for millennia.