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| Hakone caldera | |
|---|---|
| Name | Hakone caldera |
| Photo caption | Lake Ashi within the caldera, viewed from Mt. Kintoki |
| Elevation m | 1438 |
| Location | Kanagawa Prefecture, Honshū, Japan |
| Range | Hakone Mountains |
| Type | Caldera, stratovolcano complex |
| Last eruption | 2015 (phreatic activity) |
Hakone caldera is a volcanic caldera complex in the Hakone Mountains of Kanagawa Prefecture, Honshū, Japan, forming a prominent geomorphic feature west of Tokyo and east of Mount Fuji. The caldera contains Lake Ashi and multiple volcanic edifices and is part of the Northeast Japan Arc system associated with subduction of the Philippine Sea Plate beneath the Eurasian Plate. The site has significant scientific importance for volcanology, geophysics, and geothermal energy, as well as cultural ties to Shinto, Buddhism, and the historical Tōkaidō (road) corridor.
The Hakone volcanic complex lies within the Suruga Trough convergent margin where the Philippine Sea Plate subducts beneath the Eurasian Plate, interacting with the Pacific Ring of Fire and regional structures such as the Izu–Bonin–Mariana Arc. Rock types include andesite, dacite, and rhyolite that record magmatic differentiation similar to other Japanese centers like Mount Fuji, Mount Hakusan, and Mount Unzen. Geophysical surveys by institutions including the Japan Meteorological Agency, the Geological Survey of Japan, and university groups from University of Tokyo and Tohoku University have imaged a complex magma chamber system, crustal faults such as the Itozawa Fault Zone, and hydrothermal conduits that influence seismicity and surface deformation observed by GPS and InSAR techniques.
Hakone's eruptive record spans several hundred thousand years with major caldera-forming events comparable in scale to eruptions at Aso Caldera and Towada Caldera. Notable explosive episodes produced widespread pyroclastic flows and ignimbrites correlated with tephra layers used in stratigraphy alongside markers like the Aira-Tn tephra and AT tephra. Historical phreatic and phreatomagmatic activity occurred during the Holocene, including documented unrest in the Edo and Meiji periods recorded by travelers on the Tōkaidō (road) and in local chronicles preserved by Hakone Shrine. Instrumental monitoring in the late 20th and early 21st centuries registered swarms of volcanic earthquakes, ground uplift, and fumarolic increases prompting alerts from the Japan Meteorological Agency and research responses from institutions such as Kyoto University.
The caldera comprises nested collapse structures, lava domes, and stratocones including peaks like Mt. Kintoki and Mt. Myōjō, and hosts crater lakes including Lake Ashi and smaller ponds analogous to features in Kusatsu-Shirane and Kikai Caldera. Rim elevations vary; geomorphology reflects successive collapse and rebuilding phases similar to complexes such as Aso and Shikotsu. Flank volcanism produced lava domes, obsidian and pumice deposits, and sector collapse scars studied in comparison to Mount St. Helens and Mount St. Augustine to interpret stability and hazards. Mapping by the National Institute of Advanced Industrial Science and Technology and regional museums documents stratigraphic sequences and tephra correlations across the Kantō region.
Active fumaroles, hot springs (onsen) like those at Hakone-Yumoto, and solfataric fields attest to a vigorous hydrothermal system tapped for local geothermal baths and investigated for power potential akin to developments at Beppu and Nasu. Geochemical analyses of gases (CO2, SO2) and waters by research groups from Hokkaido University and Tokyo Institute of Technology inform models of magmatic degassing and reservoir temperatures. Geothermal gradients and permeability controlled by faults underpin resource assessments conducted with agencies including the New Energy and Industrial Technology Development Organization (NEDO). Hydrothermal alteration also modifies rock strength and influences landslide susceptibility along routes like the Hakone Turnpike.
The caldera lies within the Fuji-Hakone-Izu National Park, supporting montane and riparian ecosystems with mixed broadleaf and conifer forests that host species recorded by the Japanese Ministry of the Environment and naturalists from institutions like National Museum of Nature and Science. Vegetation gradients and endemic flora/fauna have been compared with biodiversity patterns on Mount Fuji and Izu Islands. Protected-area management balances conservation of habitats, cultural sites including Hakone Shrine, and visitor use, while studies by Rikkyo University and municipal authorities monitor impacts from invasive species and climate-driven range shifts.
Hakone has deep historical significance along the Edo-period Tōkaidō (road) with checkpoints, post towns, and pilgrim routes featured in artworks by Utagawa Hiroshige and Katsushika Hokusai. Religious associations center on Hakone Shrine and mountain worship traditions linked to Shugendō practitioners; pilgrims and daimyo processions historically traversed passes that feature in documents from the Tokugawa shogunate. Modern infrastructure—railways like the Hakone Tozan Railway, highways, and cable cars—interacts with archaeological sites, hot springs, and cultural landscapes protected by local governments and prefectural boards.
The caldera is a major destination for domestic and international tourism, offering attractions such as sightseeing cruises on Lake Ashi, the Hakone Ropeway, museums like the Hakone Open-Air Museum, and access to hiking routes used by visitors from Tokyo Station and travelers on the Tōkaidō Shinkansen. Outdoor recreation includes trekking on trails to summits like Mt. Kintoki, winter sports at nearby resorts, and onsen bathing at Hakone-Yumoto; visitor management and hazard communication are coordinated by Kanagawa Prefecture, the Japan National Tourism Organization, and local tourism bureaus to mitigate volcanic risk and protect cultural assets.
Category:Calderas of Japan Category:Volcanoes of Kanagawa Prefecture