Volcanoes in Japan

Japan has 105 Holocene volcanoes — the second-highest count of any nation on Earth, behind only the [[country:united-states|United States]] (165) — distributed along four distinct volcanic arcs that span the 3,000 km length of the Japanese archipelago. These 105 volcanoes include 64 [[special:types-of-volcanoes|stratovolcanoes]], 16 calderas, 7 complex volcanoes, 5 lava dome groups, and numerous other volcanic landforms. At least 64 have produced historically observed eruptions, and an extraordinary 21 have erupted since the year 2000, making Japan one of the most volcanically restless nations on the planet.

Japan's volcanic intensity stems from its position at the junction of four tectonic plates: the Pacific Plate, the Philippine Sea Plate, the Eurasian Plate, and the North American Plate. The subduction of the Pacific and Philippine Sea Plates beneath the Japanese islands generates the magma that feeds the archipelago's volcanic arcs, while the complex plate interactions produce the devastating earthquakes for which Japan is equally famous. This volcanic activity is concentrated along the [[special:ring-of-fire|Ring of Fire]], and Japan alone accounts for roughly 7% of the world's active volcanoes.

Japanese volcanoes have produced some of the most powerful eruptions in the Holocene record, including the VEI 7 eruption of Kikai caldera around 4350 BCE — the largest volcanic event in the Japanese islands during the last 10,000 years — and the VEI 5 Hōei eruption of [[volcano:fujisan|Mount Fuji]] in 1707, which deposited volcanic ash on Edo (modern Tokyo). The Japan Meteorological Agency (JMA) continuously monitors 50 volcanoes through a network of seismometers, tiltmeters, GPS stations, and cameras, and maintains a [[ext:https://www.data.jma.go.jp/svd/vois/data/tokyo/STOCK/activity_info/map_0.html|volcanic alert level system]] ranging from Level 1 (normal) to Level 5 (evacuation). Today, approximately 10% of the world's population living near active volcanoes resides in Japan, making volcanic risk management a defining challenge of Japanese governance and civil engineering.

Japan's extraordinary volcanic density is the direct result of its position atop one of the most tectonically complex convergence zones on Earth. The Japanese archipelago sits where four major tectonic plates collide: the Pacific Plate subducts westward beneath the North American Plate at the Japan Trench (at approximately 8–10 cm per year), while the Philippine Sea Plate subducts northwestward beneath the Eurasian Plate at the Nankai Trough and Ryukyu Trench (at approximately 3–5 cm per year). These dual subduction systems create four distinct volcanic arcs across Japan.

The **Kuril Volcanic Arc** extends through eastern Hokkaido, generated by Pacific Plate subduction at the Kuril Trench. This arc includes volcanoes like Tokachidake, Taisetsuzan, and Maruyama. The **Northeast Japan Volcanic Arc** runs through northern and central Honshu, also driven by Pacific Plate subduction at the Japan Trench.

This is the most volcano-dense arc in Japan, containing 40 volcanic centers including [[volcano:asamayama|Asamayama]], Bandaisan, Nasudake, Azumayama, and Iwatesan. The **Izu Volcanic Arc** extends south from the Izu Peninsula through the Izu and Ogasawara (Bonin) island chains into the western Pacific, generated by Pacific Plate subduction beneath the Philippine Sea Plate. Mount Fuji sits at the junction of this arc with the main Honshu arc.

The **Nankai and Ryukyu Volcanic Arcs** extend through western Honshu, Shikoku, Kyushu, and the Ryukyu Islands, driven by Philippine Sea Plate subduction.

Kyushu is particularly volcanic because it sits above the intersection of the Philippine Sea Plate subduction zone and a back-arc rift system. This combination has produced some of Japan's largest calderas, including Aira (containing Kagoshima Bay and [[volcano:sakurajima|Sakurajima]]), Ata, Kikai, and [[volcano:asosan|Asosan]] — the largest caldera in Japan at 25 by 18 km. The concentration of large caldera systems in southern Kyushu represents one of the highest caldera densities anywhere on Earth.

Japan does not sit on any divergent boundary — unlike [[country:iceland|Iceland]], all of Japan's volcanism results from subduction. However, back-arc spreading behind the main subduction zones has opened features like the Sea of Japan and contributed to localized extensional volcanism in some regions.

**Mount Fuji (Fujisan)** — Japan's tallest peak and most iconic volcano, [[volcano:fujisan|Mount Fuji]] rises to 3,776 m (12,388 ft) as a nearly symmetrical [[special:types-of-volcanoes|stratovolcano]] visible from Tokyo on clear days. With 58 confirmed eruptions, Fuji is the fifth most active volcano in Japan. Its last eruption — the Hōei event of 1707 (VEI 5) — deposited 4–5 cm of ash on Edo (Tokyo), 100 km to the northeast.

Japanese volcanologists consider another eruption of Fuji to be inevitable; the current repose period of over 300 years exceeds many previous inter-eruption intervals. A Fuji eruption today would disrupt the Tokyo metropolitan area (population ~38 million) with ashfall, potentially grounding aviation across central Japan. Mount Fuji is a UNESCO World Heritage Site and receives over 200,000 climbers annually during the July–August season.

**Asosan (Mount Aso)** — The most frequently erupting volcano in Japan with 172 confirmed eruptions, [[volcano:asosan|Asosan]] on the island of Kyushu features one of the largest calderas in the world — measuring 25 by 18 km. The caldera, formed by a series of massive eruptions between 270,000 and 90,000 years ago, now contains a city of approximately 50,000 people. The active Nakadake cone within the caldera erupts regularly with Strombolian and phreatic explosions; its most recent activity was in 2021.

Aso's caldera-forming eruptions rank among the largest in Japan's geological history, with the Aso-4 eruption approximately 90,000 years ago producing pyroclastic flows that covered much of Kyushu.

**Asamayama** — Central Honshu's most active volcano, [[volcano:asamayama|Asamayama]] is a 2,568 m (8,425 ft) complex volcano with 129 confirmed eruptions — the second-highest count in Japan. Its VEI 5 eruption in 1108 CE was one of the largest historical eruptions in Japan. The catastrophic 1783 eruption produced pyroclastic flows and a massive debris avalanche that killed approximately 1,500 people and dammed a river, creating a natural dam whose subsequent failure caused further devastation.

Asamayama last erupted in 2019 and is continuously monitored by JMA.

**Sakurajima (Aira)** — One of the world's most persistently active volcanoes, [[volcano:sakurajima|Sakurajima]] rises 1,117 m from Kagoshima Bay within the massive Aira caldera in southern Kyushu. With 48 confirmed eruptions in the Smithsonian database, Sakurajima has been in near-continuous eruption since 1955, producing hundreds of Vulcanian explosions per year — sometimes exceeding 1,000 explosions annually. The city of Kagoshima (population ~600,000) sits just 8 km across the bay and routinely receives ashfall.

The dramatic Taishō eruption of 1914 (VEI 4) produced enough lava to connect the formerly separate island of Sakurajima to the Ōsumi Peninsula.

**Kirishimayama** — A volcanic complex of over 20 cones and craters in southern Kyushu, Kirishimayama has produced 79 confirmed eruptions and was active as recently as 2025. The Shinmoedake cone erupted dramatically in 2011 in a sub-Plinian event (VEI 3) that was closely monitored and widely photographed. The Kirishima range is a popular hiking destination and is protected within Kirishima-Kinkowan National Park.

**Kusatsu-Shiranesan** — A stratovolcanic complex in the Gunma Prefecture of central Honshu, Kusatsu-Shiranesan has 28 confirmed eruptions and produced a deadly phreatic eruption in January 2018 that killed one person and injured 11 near a ski resort — a stark reminder that even small, sudden eruptions at Japanese volcanoes can be lethal due to the proximity of tourism and recreation infrastructure.

**Miyakejima** — Located 180 km south of Tokyo in the Izu island chain, Miyakejima is a basaltic-andesitic stratovolcano with 39 confirmed eruptions. Its major 2000 eruption caused the complete evacuation of the island's approximately 3,800 residents, who could not return for over four years due to persistent toxic volcanic gas emissions (primarily SO₂).

**Ontakesan** — Mount Ontake, at 3,067 m (10,062 ft), is the second-tallest volcano in Japan and the site of the country's deadliest volcanic disaster in modern history. On September 27, 2014, a sudden phreatic eruption at the summit killed 63 hikers — many caught in a dense shower of ballistic rocks while enjoying autumn foliage near the summit. The tragedy led to a comprehensive review of Japanese volcano monitoring and alert systems.

**Suwanosejima** — A remote stratovolcano in the Ryukyu chain between Kyushu and Okinawa, Suwanosejima is one of Japan's most persistently active volcanoes. It has been in near-continuous Strombolian eruption for decades and was active in 2025.

**Kikai** — The submarine Kikai caldera off the southern coast of Kyushu produced Japan's most powerful Holocene eruption: the VEI 7 Akahoya eruption approximately 6,300 years ago (around 4350 BCE). This catastrophic event devastated the Jōmon-period population of southern Kyushu. The caldera, 19 km in diameter, remains active — a growing lava dome was discovered on the caldera floor in 2018, and the volcanic system showed surface activity in 2025.

**Bandaisan** — The 1888 eruption of Mount Bandai in Fukushima Prefecture was a landmark event in Japanese volcanology. A sudden phreatic explosion caused the collapse of the volcano's northern flank, producing a debris avalanche that killed 477 people and created the scenic Goshikinuma (Five Colored Lakes) that are now a major tourist attraction.

**Tokachidake** — A stratovolcanic complex in central Hokkaido with 27 confirmed eruptions, Tokachidake last erupted in 2004. Its 1926 eruption triggered a lahar that destroyed the town of Kami-Furano, killing 144 people — one of the deadliest volcanic disasters in 20th-century Japan.

Japan's volcanic history is among the most prolific and devastating of any country on Earth. The archipelago's 105 volcanoes have collectively produced 1,738 documented eruptions, including 115 events of VEI 4 or greater — an extraordinary concentration of high-magnitude volcanism that reflects Japan's position above multiple subduction zones.

The most cataclysmic eruption in Japan's Holocene record was the VEI 7 Akahoya eruption of Kikai caldera approximately 6,300 years ago (around 4350 BCE). This super-colossal event devastated the Jōmon-period civilization of southern Kyushu, producing pyroclastic flows that raced across the sea surface for up to 100 km and depositing the widespread Akahoya tephra layer identifiable in sediment cores across all of Japan and far into the Pacific Ocean. The eruption ejected an estimated 150 km³ of material, making it one of the largest volcanic events of the Holocene worldwide.

The massive VEI 6 caldera-forming eruption of Mashu in Hokkaido around 5550 BCE created the stunningly clear caldera lake now regarded as one of Japan's most beautiful natural features. Multiple VEI 5 eruptions at Towada, Shikotsu, Hokkaido-Komagatake, and Myokosan shaped the landscape of northern Japan throughout the early and middle Holocene.

In the historical period, Japan's most significant eruptions include the VEI 5 eruption of [[volcano:asamayama|Asamayama]] in 1108 CE, which devastated surrounding agricultural land and was recorded in contemporary chronicles; the VEI 5 Towada eruption of 915 CE, the largest historical eruption in northern Honshu; the VEI 5 Hōei eruption of [[volcano:fujisan|Mount Fuji]] in 1707, which deposited ash on Edo (Tokyo) and was triggered just 49 days after the devastating M8.7 Hōei earthquake; and the VEI 5 eruptions of Hokkaido-Komagatake in 1640 (which triggered a tsunami killing approximately 700 people) and Shikotsu in 1667 and 1739.

The 1783 eruption of Asamayama killed approximately 1,500 people through pyroclastic flows and secondary debris flows, making it one of the deadliest eruptions in Japanese history. The 1888 collapse of Bandaisan killed 477 people and became a landmark case study in volcanic debris avalanches. The 1914 Taishō eruption of Sakurajima (VEI 4) was one of the 20th century's largest eruptions in Japan, producing lava flows that permanently connected Sakurajima to the mainland.

The 21st century has brought continued vigorous activity, including Miyakejima's 2000 eruption and prolonged degassing crisis, the catastrophic 2014 Ontakesan phreatic eruption (63 deaths), the 2011 Shinmoedake eruption, and ongoing activity at Sakurajima, Suwanosejima, Asosan, and Kikai. The 2021 eruption of Fukutoku-Oka-no-Ba created a temporary new island in the Ogasawara chain.

Japan faces an exceptionally diverse range of volcanic hazards, compounded by the country's high population density and the proximity of urban areas, transportation networks, and tourism infrastructure to active volcanic centers.

Pyroclastic flows represent the most lethal threat. Historical pyroclastic flows from Asamayama (1783), Unzen (1991, killing 43 including volcanologists), and the Kikai caldera system have demonstrated their devastating speed and reach. The greatest catastrophic risk comes from a potential large-scale caldera eruption in southern Kyushu — a study by the Kobe Ocean-Bottom Exploration Center estimated that a VEI 7 eruption at Aira or Kikai could produce pyroclastic flows reaching across much of Kyushu, potentially affecting millions of people.

Ashfall from a major eruption poses severe risks to Japan's densely populated urban centers. Government modeling of a Mount Fuji eruption scenario suggests that 2–10 cm of ash could accumulate across the greater Tokyo metropolitan area (population ~38 million), disrupting rail networks, clogging water treatment systems, collapsing roofs, grounding all aviation, and causing economic damage estimated at ¥2.5 trillion (∼$17 billion USD).

Lahars (volcanic mudflows) are particularly dangerous at snow- and glacier-capped volcanoes in Hokkaido and northern Honshu. The 1926 Tokachidake lahar killed 144 people in Kami-Furano. Volcanic debris avalanches, such as the 1888 Bandaisan collapse, can travel at high speeds and dam rivers, creating secondary flood hazards.

Phreatic (steam-driven) eruptions pose a uniquely challenging hazard in Japan because they can occur with little or no warning at popular tourist and recreation destinations. The 2014 Ontakesan disaster demonstrated this vulnerability: 63 hikers died in an eruption that produced no clear precursory signals detectable by existing monitoring equipment. Volcanic gas emissions, particularly sulfur dioxide and hydrogen sulfide, create chronic hazards at Sakurajima, Miyakejima, and other degassing volcanoes.

The JMA operates a five-level volcanic alert system and monitors 50 volcanoes through its nationwide network. Japan is also a global leader in volcano research and hazard engineering, with innovations including lahar-resistant concrete barriers (sabo dams), volcanic shelters on popular hiking trails (installed after the 2014 Ontake disaster), and real-time ash-dispersion modeling systems.

Japan's 105 volcanoes are distributed along four major volcanic arcs that collectively span the archipelago from Hokkaido in the north to the Ryukyu Islands in the south.

The **Northeast Japan Volcanic Arc** is the most densely volcanic zone, containing 40 volcanic centers across northern and central Honshu. This arc runs roughly parallel to the Pacific coast, approximately 200–300 km inland from the Japan Trench. Notable volcanoes include Asamayama, Bandaisan, Azumayama, Nasudake, Iwatesan, and Chokaisan.

The volcanic front here is clearly defined and results from Pacific Plate subduction at 8–10 cm/year.

The **Izu-Ogasawara Volcanic Arc** extends south from the Izu Peninsula through the Izu Islands (Izu-Oshima, Miyakejima, Hachijojima) and the Ogasawara (Bonin) Islands. This arc contains 27 volcanoes (17 Izu + 10 Ogasawara) and includes both emerged islands and numerous submarine volcanoes. Mount Fuji sits at the complex junction where the Izu Arc meets the Northeast Japan Arc.

The **Nankai Volcanic Arc** runs through western Honshu and Kyushu, containing 13 volcanic centers including Asosan, Kujusan, Ontakesan, Yakedake, and Hakusan. The **Ryukyu Volcanic Arc** extends from southern Kyushu through the Ryukyu Islands toward Taiwan, with 13 volcanic centers including Sakurajima (within the Aira caldera), Kirishimayama, Suwanosejima, and the submarine Kikai caldera.

The **Kuril Volcanic Arc** passes through eastern Hokkaido with 10 volcanic centers, including Tokachidake, Taisetsuzan, and Akan. Two additional volcanoes in the Mariana Arc are attributed to Japan in the Smithsonian database.

Volcanism is inseparable from Japanese culture, spirituality, and national identity. [[volcano:fujisan|Mount Fuji]], designated a UNESCO World Heritage Site in 2013 as a "Cultural Site" rather than a natural one, has been a subject of art, poetry, and spiritual pilgrimage for over a thousand years. Katsushika Hokusai's "Thirty-Six Views of Mount Fuji" (c. 1831) — including the iconic "The Great Wave off Kanagawa" — is among the most recognizable works of art in history. Fuji is considered sacred in both Shinto and Buddhist traditions, with shrines at its summit and along pilgrimage routes.

Volcanic hot springs (onsen) are one of Japan's most important cultural and economic assets. The country has over 27,000 hot spring sources and approximately 3,000 onsen resorts, generating an estimated ¥1.7 trillion ($12 billion USD) in annual tourism revenue. Famous volcanic onsen towns include Beppu (near Asosan), Hakone (near Hakone caldera), Kusatsu (near Kusatsu-Shiranesan), Noboribetsu (near Shikotsu caldera), and Ibusuki (near Aira caldera).

Geothermal energy, while underutilized relative to Japan's volcanic potential due to conflicts with onsen regulations and national park designations, provides approximately 0.2% of the country's electricity through 17 operating geothermal power plants.

Volcanic soil (andosol) supports Japan's agricultural sector, particularly rice cultivation in volcanic ash plains across Kyushu and the Tōhoku region. The aesthetic beauty of volcanic landscapes — calderas, crater lakes, volcanic islands, and autumn foliage framed against volcanic peaks — drives a significant portion of domestic and international tourism. Japan's volcanic heritage has also made it a global leader in volcanology research, with institutions like the Earthquake Research Institute at the University of Tokyo and the National Research Institute for Earth Science and Disaster Resilience (NIED) at the forefront of monitoring and prediction technology.

Japan offers world-class volcanic tourism, with many active volcanoes accessible by public transportation and equipped with excellent visitor infrastructure. [[volcano:fujisan|Mount Fuji]] is the most popular volcanic destination, with over 200,000 climbers summiting during the official July–August season via four established trails. The Fuji Five Lakes region at the volcano's base draws millions of additional visitors year-round for sightseeing, photography, and onsen bathing.

[[volcano:asosan|Asosan]] (Mount Aso) in Kyushu allows visitors to drive or take a ropeway to the rim of the active Nakadake crater when alert levels permit, offering views directly into the steaming vent — one of the most accessible views of an active volcanic crater anywhere in the world. The surrounding Aso Kuju National Park features volcanic grasslands, onsen towns, and the dramatic caldera landscape.

[[volcano:sakurajima|Sakurajima]] can be reached by a 15-minute ferry from Kagoshima city. The Sakurajima Visitor Center and several observation points provide views of the frequently erupting volcano. Kagoshima's residents live with ash-fall as a routine part of life, and the city distributes special ash-collection bags.

Hakone, just 80 km from Tokyo, offers hot springs, the volcanic Owakudani valley with its famous black eggs boiled in sulfurous springs, and views of Fuji. The Kirishima range in southern Kyushu provides excellent volcanic hiking. Noboribetsu in Hokkaido features the spectacular Jigokudani (Hell Valley) thermal area near the Shikotsu–Toya National Park, where visitors can see the calderas of both Shikotsu and Toya.

Japan's volcanic alert levels should always be checked before visiting active volcanoes through the JMA website. After the 2014 Ontake disaster, many volcanic peaks have been equipped with concrete shelters for hikers.