Mount Ontake: The Sacred Peak and the Silent Killer

Standing at 3,067 meters (10,062 feet), Mount Ontake (Ontake-san) is the second-highest volcano in Japan, surpassed only by the iconic Mount Fuji. Straddling the border of Nagano and Gifu prefectures, it is a massive, sprawling complex of overlapping stratovolcanoes that dominates the Kiso Valley.

For over a thousand years, Ontake has been a mountain of peace and prayer. It is one of the holiest sites in Shugendo (mountain asceticism) and the birthplace of the unique Ontake-kyo faith. Pilgrims dressed in white robes have climbed its slopes for centuries to purify their spirits in its icy waterfalls and touch the sky.

But on September 27, 2014, this peaceful legacy was shattered. On a bright autumn Saturday, crowded with hikers enjoying the fall colors, the mountain exploded without warning. It became the site of the deadliest volcanic disaster in post-war Japan, a tragedy that changed how the nation monitors and respects its fiery giants.

The 2014 Eruption: A Tragedy in Blue Skies

The events of September 27, 2014, serve as a harrowing reminder of nature’s unpredictability.

The Setting

It was the peak of the koyo (autumn foliage) season. The sky was an brilliant cloudless blue. Hundreds of hikers—families, retirees, children—were on the trails, enjoying the vibrant reds and oranges of the changing leaves. It was lunch time, and the summit area near the shrine was packed with people eating bento boxes and taking photos.

The Explosion

At 11:52 AM, there was a sound like a thunderclap. Without any significant precursor earthquake felt by the hikers, the ground cracked open near the summit.

The Phreatic Blast: This was not a magmatic eruption (where molten rock rises). It was a phreatic eruption (steam-blast). Groundwater had seeped into the hot interior of the mountain, flashed instantly into superheated steam, and blasted through the rock like a pressure cooker lid blowing off.
The Gray Wall: Survivors described seeing a “wall of gray” rushing towards them. It wasn’t just gas; it was a pyroclastic density current—a fast-moving avalanche of hot ash, rocks, and gas.
Zero Visibility: In seconds, the blue sky turned to pitch black. The temperature dropped, then rose. Hikers were pelted with a rain of rocks ranging from pebble-sized to the size of watermelons.

The Aftermath

The eruption killed 63 people (including 5 whose bodies were never recovered).

The “Stealth” Eruption: Why was there no warning? Magmatic eruptions are usually preceded by days of “volcano-tectonic” earthquakes as magma breaks rock. Phreatic eruptions are notoriously silent. The Japan Meteorological Agency (JMA) had detected minor tremors in early September, but nothing that signaled an imminent blast.
The Rescue: The rescue operation was the largest in Japanese history, involving over 1,000 police, firefighters, and Self-Defense Force personnel. It was hampered by ongoing volcanic activity, toxic gas, and the onset of a typhoon.

The Spiritual Mountain: Ontake-Shinko

Before it was a disaster site, Ontake was—and remains—a cathedral of nature.

The Origins of Worship

Since ancient times, Japanese people have believed that mountains are the dwelling places of kami (spirits) and the destination of the souls of the dead. Ontake is considered one of the most powerful spiritual “power spots” in Japan.

Shugendo: The mountain attracts practitioners of Shugendo, a syncretic religion combining Shinto nature worship, Buddhist esotericism, and Taoist magic. Practitioners, called Yamabushi, perform grueling physical feats to gain spiritual power.
Ontake-kyo: In the Edo period, a specific sect called Ontake-kyo formed. Unlike other mountain cults that were reserved for ascetics, Ontake-kyo opened the mountain to common people. They established “Ko” (confraternities) or pilgrim groups that would travel together to the mountain.

The Purification Rituals

The journey up Ontake is not just a hike; it is a ritual of death and rebirth.

Takigyo (Waterfall Meditation): The base of the mountain is ringed with sacred waterfalls, most notably Kiyotaki and Shintaki. Pilgrims stand underneath the freezing, pounding water, chanting the Hannya Shingyo (Heart Sutra). This washes away kegare (spiritual impurity) before they set foot on the holy ground.
The White Robes: Pilgrims wear white sugegasa hats and white robes (shiro-shozoku). In Japanese culture, white is the color of death. By wearing it, the pilgrim signifies that they are dead to the secular world and ready to enter the realm of the spirits. If they die on the mountain, they are already dressed for their funeral.
Remains: The trail is lined with thousands of stone monuments called reijin-hi. These are memorials to the spirits of ancestors and devout believers who have passed away, their souls believed to have returned to the mountain.

Geological Context

Ontake is a complex beast. It is not a single cone like Fuji, but a massive ridge of overlapping vents and craters extending over 3 kilometers north to south.

The Sleeping Giant Myth

For a long time, Ontake was thought to be extinct.

Pre-1979: Before 1979, geologists believed Ontake hadn’t erupted for thousands of years. It was covered in deep forest and alpine plants.
1979 Awakening: The mountain rudely disproved this theory on October 28, 1979, with a moderate eruption that ejected over 200,000 tons of ash. This event rewrote the textbooks on Japanese volcanology, forcing a re-evaluation of “extinct” volcanoes across the archipelago.
1991 and 2007: Minor phreatic eruptions occurred again, culminating in the 2014 disaster.

The Dragon Lakes

The summit area is dotted with five crater lakes, known as the “Five Ponds of Ontake.”

Ni-no-Ike: At 2,905m, this is the highest mountain lake in Japan. Its water is a stunning turquoise blue. It acts as a holy water source; pilgrims bottle it to take home for healing rituals.
San-no-Ike: The deepest of the lakes, often frozen well into the summer. Legend says a dragon god lives in its depths, and throwing a stone into the water will summon a storm.
Jigoku-dani (Hell Valley): Not a lake, but a fumarolic area where active vents release sulfurous gas, staining the rocks yellow and white. The ground here is warm to the touch, a reminder of the heat beneath.

Alpine Life: A Sky Island

Despite its volatility, Mount Ontake is a biodiversity hotspot, acting as a “sky island” for alpine species.

The雷ichō (Thunder Bird)

The symbol of Japan’s high mountains, the Rock Ptarmigan (Lagopus muta japonica), lives on the rocky slopes near the summit. Known as Raichō (“Thunder Bird”), they are believed to be messengers of the gods. They change color with the seasons—brown in summer to match the rock, and pure white in winter to blend with the snow. They are a protected species and seeing one is considered a sign of good luck.

Gentle Giants: The Komakusa

The slopes are also home to the Komakusa (Pixie’s Parasol), known as the “Queen of Alpine Plants.” These delicate pink flowers grow in the harsh gravel of the volcanic wasteland, their long root systems anchoring them against the fierce winds.

The Mediators: Oza and Nakaza

A unique aspect of the Ontake-kyo faith is the practice of spiritual mediumship, known as Oza-Tate.

The Ritual: It involves a team of two or three people. The Nakaza (medium) sits in a trance state, inviting a deity or spirit to possess their body. The Maeza (interrogator) asks questions of the spirit, while the Waki-za (assistant) supports the medium.
Divine Healing: Pilgrims often consult these mediums on the mountain to ask for advice on illness, business, or family matters. It is one of the few surviving examples of shamanistic possession rituals in modern Japan.
The Go-o-ho: Practitioners also create rigorous paper talismans called Go-o-ho. These are printed with woodblocks on the mountain and sometimes swallowed by sick believers as a form of spiritual medicine.

Recovery and Reopening

The 2014 eruption closed the mountain for years. The recovery has been a slow, painful process of physical and spiritual healing.

New Safety Measures

Japan learned hard lessons from Ontake.

Shelters: Reinforced concrete shelters (made of Kevlar and steel) have been built near the summit to protect hikers from falling rocks (ballistics), which were the primary cause of death in 2014.
Monitoring: The mountain is now wired with dozens of new tiltmeters, seismometers, and GNSS stations.
The Zone System: Access is now strictly controlled. The “exclusion zone” around the crater was lifted for the Kengamine summit in 2018, but only during specific seasons and routes. Hikers are now strongly encouraged (and often required) to submit hiking plans and carry helmets.

The Return of the Pilgrims

Despite the tragedy, the faithful have returned. The sound of the conch shell trumpet (horagai) blown by Yamabushi echoes once again through the forests. The locals of Kiso and Otaki villages, whose livelihoods depend on tourism, have worked tirelessly to restore the trails.

Conclusion

Mount Ontake is a mountain of duality. It is a place where the veil between the living and the dead is thin. For centuries, this meant a spiritual connection—a place to speak with ancestors. In 2014, it meant a literal transition.

Today, climbing Ontake is a somber experience. As you pass the new concrete shelters and the memorials to the 63 victims, the beauty of the emerald lakes and the sea of clouds is tinged with a deep respect for the volatility of the Earth. It stands as a monument to the Japanese concept of Mono no aware—the pathos of things, the beautiful sadness of the impermanence of life.