Mt. Mihara Summit & Crater

About

Mt. Mihara summit crater showing active volcanic terrain

Mt. Mihara (三原山, Mihara-yama) is an active volcano rising 758 meters above sea level at the center of Izu Oshima Island, part of Tokyo Prefecture. This pyroclastic cone serves as the island's dominant geological feature and spiritual center, revered by locals as "Gojinka-sama" (Lord Sacred Fire) or "Mihara-daimyojin." 🔗

The volcano remains active with periodic eruptions every 30 to 40 years, most recently in 1990. Currently maintained at Volcanic Alert Level 1 (Be mindful that the volcano is potentially active), the lowest level on Japan's volcanic warning system, indicating normal background activity with weak emitting activity in the crater and ground deformation observation showing the island has been expanding. 🔗

November offers excellent conditions for Mt. Mihara hiking with cooler temperatures (17°C day/11-13°C evening), reduced humidity improving air clarity, and a 57% likelihood of seeing Mt. Fuji from the summit. October and November are the best months for Mt. Fuji visibility as the weather turns cooler and drier, with fewer clouds blocking the view. 🔗

Cultural & Religious Significance

Mt. Mihara embodies a profound spiritual tradition where volcanic power transforms into cultural reverence. The Oshima people call their mountain "Gojinka" (sacred fire), immortalized in a famous folk love song: "I was raised by Oshima's sacred fire, smoke forever rising in my heart." 🔗

Long ago, exploding magma would create a red sky that islanders revered as manifestation of the divine, reflecting ancient animistic beliefs that deified natural forces humans could not control. Mt. Mihara has been revered and feared as "Goshinka-sama" (Lord Sacred Fire), representing how the islanders transformed what could be seen as an ominous natural force into a romantic and spiritual symbol maintained throughout generations. 🔗

The theme of the Izu Oshima Geopark centers on how to live in harmony with the volcano and protect the island's unique culture and ecosystem, with residents living "not at the foot of a volcano, but in the middle of a volcano." 🔗

The 1986 Eruption: Community Resilience

The November 1986 eruption stands as a defining moment in Oshima's modern history and demonstrates extraordinary community resilience. Beginning at 17:18 on November 15, the eruption initially produced lava fountains up to 500 meters high within the crater. On November 21, the first eruptive activity outside the caldera began at 17:46 from a 1.5-kilometer-long fissure northwest of the caldera rim, with lava fountains reaching up to 1.6 kilometers high and achieving a Volcanic Explosivity Index of 3. 🔗

Lava flows advanced to within 1 kilometer of Motomachi, the island's main town on the west coast, prompting the largest evacuation operation during a natural disaster in Japan's history. All 10,200 residents and 2,000 tourists were evacuated in less than 12 hours using 39 vessels on the night of November 21-22. 🔗

Remarkably, just hours before the major eruption on November 21, 5,200 of the 10,000 residents had participated in evacuation drills using six ships, 20 planes, and 145 motor vehicles, which likely contributed to the successful evacuation that evening. 🔗

Cultural symbols survived miraculously: Mihara Shrine escaped destruction when a ridge of hardened lava just above the shrine split the approaching lava flow, diverting it around the building before it merged further down the slope. 🔗

Since the 1986 eruption, the island has transformed the volcanic landscape into an educational and recreational resource. Routes like "Komorebi Tunnel," "Someday a Forest," and "Geo Rock Garden" allow visitors to witness natural environment restoration after the eruption. The island's designation as a Japan Geopark in 2010 has facilitated active geoguide training programs, maintaining the balance between tourism and volcanic awareness. 🔗

Visiting Information

Access:

• Ferry from Tokyo: High-speed jet boat from Tokyo Takeshiba Ferry Terminal, 2 hours to Oshima Island 🔗
• Alternative: 25-minute flight from Tokyo's airports 🔗
• From Port to Trailhead: Rental car essential for November visits (bus service unavailable off-season) 🔗

Hours: Mountain accessible year-round, 24 hours. The hiking trail has no restricted access hours. 🔗

Admission: Free. No entrance fee is charged for Mt. Mihara itself. 🔗

Best time to visit: November is ideal for Mt. Mihara hiking. Cooler temperatures (17°C during the day, 11-13°C in the evening) provide comfortable hiking conditions. October and November offer superior Mt. Fuji visibility as weather turns cooler and drier with fewer clouds, achieving a 57% likelihood of mountain visibility. 🔗

Early morning offers the best visibility and lighting conditions. Heavy fog can compress vision, so choosing clear days is essential for optimal views. 🔗

Current status: Active volcano at Alert Level 1 (Be mindful that the volcano is potentially active). Weak emitting activity continues in the crater with ground deformation observation showing island expansion. 🔗

The Summit Hike Experience

Two routes lead to the summit from the observatory, both steep in sections but not overly strenuous: a paved asphalt path and an unpaved route meandering over fine lava sand, grassy areas, gravelly patches, and rugged stretches strewn with jagged rocks. 🔗 The trails are well-marked and cover diverse natural landscapes from foggy rainforests to desert-like atmospheres created from recent eruptions. 🔗

Reaching the summit takes 45 minutes on foot from Mihara-sanchoguchi Bus Stop, with the full course covering 7.9 kilometers and typically requiring 2-2.5 hours to complete. While Mt. Mihara is rated as moderately challenging, the trails are not steep and can be easily climbed without strenuous effort, making them accessible to families with small children. 🔗

Crater Rim Walk (Ohachi-Meguri Course)

The Ohachi-meguri hiking trail encircles the volcanic crater in a dramatic 2.5-kilometer unpaved circuit. The crater measures approximately 350 meters in diameter and 200 meters deep, with white steam rising from the bottom and surroundings, heated by underground magma. 🔗

The trail passes numerous fumarole vents emitting water vapor heated by magma lying close to the surface, creating an otherworldly atmosphere that visitors describe as "being on another planet." 🔗 The popular 45-minute Ohachimeguri trail leads hikers past these fumaroles and steam vents, with the full loop around the crater taking approximately one hour. 🔗

Volcanic Landscape Features

1986 Lava Fields: On the approach to the summit, hikers pass the hardened lava fields from the 1986 eruption, now transformed into black, sharp rocks with a unique and spooky atmosphere. 🔗

Urasabaku (Black Desert): On the "Urasabaku" trail, hikers walk through Japan's only officially designated "desert" on GSI maps—a field of black sand created by lava spat out during volcanic eruptions, resembling the surface of the moon. 🔗

Texas Route: The aptly named Texas Route features craggy rock outcrops jutting out of sandy lava with clumps of low grasses stretching to the horizon, resembling scenes from the Old West. 🔗

Panoramic Views

From the summit and crater observation deck, breathtaking panoramas extend in all directions on clear days:

• Mt. Fuji to the north 🔗
• Izu and Chiba peninsulas to the west and east 🔗
• Other Izu Islands to the southwest, including the perfectly pointed cone of Toshima 🔗
• Izu Peninsula and Hakone in the distance 🔗
• Pristine blue waters contrasting against desolate volcanic terrain 🔗

Practical Visiting Tips

Essential Gear and Preparation:

• Bring plenty of water as there is no shade on the mountain and public facilities including vending machines are scarce 🔗
• Wear sunscreen and protective clothing since there's no shade 🔗
• Windproof layers are essential—it can get quite windy 🔗
• Bring an extra jacket for the crater area even if the day is warm at lower elevations 🔗
• Sturdy hiking shoes are recommended for rocky, volcanic terrain 🔗

Safety Considerations: Mt. Mihara is an active volcano carefully monitored at Alert Level 1. Helmets are available for free rental at summit entrance buildings for those seeking extra protection from volcanic projectiles. Shelters along the hiking path and the observation deck provide temporary protection from volcanic projectiles and volcanic ash. 🔗

November Weather Considerations: November temperatures on Mt. Mihara average 17°C during the day and 11-13°C in the evening. Depending on weather conditions, it can be quite cold and windy by the crater—bring an extra jacket even if it's a warm and sunny day at sea level. Windproof layers are essential as the summit can get quite windy. 🔗

Photography Conditions:

• Best Photo Spots: Crater Rim Trail (Ohachi-Meguri Course), Crater West Lookout, Gravel Path for Higher Views
• Lighting Recommendations: Early morning provides optimal lighting conditions and the clearest air for photography 🔗
• Photogenic Features: White steam rising from the crater, dynamic central crater and Izu Islands views, Ura-Sabaku black desert landscape, Mt. Fuji from the crater observation deck (November offers exceptional visibility) 🔗

Crowd Avoidance: November falls outside the peak tourist season, offering a less crowded experience. Early morning hikes provide both optimal lighting conditions and the fewest fellow hikers. 🔗

Visitor Experience Insights: Visitors consistently describe the Mt. Mihara hike positively, with common themes including: "Not really that tiring so families with small children can make the hike," "A gorgeous hike that was not difficult," and "The view from the top was loved by visitors." 🔗

Location: View on Google Maps

Source: attractions/ooshima/mt-mihara-summit-crater.md