Japan is synonymous with volcanoes, earthquakes, and a vibrant nature that, over the centuries, has shaped not only the country's geography but also its culture, beliefs, and approach to life. From the ancient calm of Mount Fuji to the underwater eruptions that create new islands in the archipelago, understanding volcanic activity in Japan means delving into a history of powerful natural processes, social resilience, and constant adaptation.
In this article, you'll discover how Japanese volcanoes are formed, what types of risks exist, how their activity is monitored, and what are the most memorable eruptions, as well as the impact of all this on the daily life and philosophy of the Japanese people. Prepare for a detailed and natural journey, where science blends with tradition and firsthand experience in one of the most fascinating countries on the planet.
The Japanese Volcanic Landscape: A Land Forged by Fire
Japan is a unique archipelago, made up of more than 14.000 islands of various sizes, although the four main ones (Honshu, Hokkaido, Kyushu and Shikoku) account for most of the population and economic activity. This arrangement is not accidental: the country is situated on the edge of the well-known Pacific Ring of Fire, a tectonic belt where seismic and volcanic activity is extremely intense.
The Japanese territory lies at the confluence of several tectonic plates: Pacific, Eurasian, North American and Philippine. Their movements are responsible for the formation and activity of the country's more than 100 active volcanoes, representing nearly 10% of the world's total. It is not surprising, therefore, that Japan suffers some 1.500 earthquakes a year and frequent episodes of eruptions, both terrestrial and underwater, which regularly alter its geographic map.
How are volcanoes formed in Japan?
Volcanic formation in Japan is the result of millions of years of geological processes associated with plate subduction. When the oceanic plate (Pacific or Philippine) slides under the Asian continent, friction generates melting of the Earth's mantle, accumulating magma that, due to pressure, rises to the surface and gives rise to Japanese volcanoes.
Volcanic activity has created not only unique mountains like Mount Fuji, but also vast lava fields, volcanic lakes, newly formed islands, and ice caves. Furthermore, each eruption contributes in some way to the reconfiguration of the territory, whether by generating new land masses, as occurred in 2023 near Ogasawara, or by dividing lakes and giving rise to natural phenomena that are now part of the local environment and culture.
Types of volcanoes and eruptions in Japan
Japan has a great diversity of volcanoes: from majestic stratovolcanoes like Fuji, to more modest cones or underwater giants. Eruptive activity is also diverse, varying between violent explosions, lava flows, ash emissions, toxic gases and phreatic episodes (where groundwater amplifies the explosiveness).
Historical examples of eruptions show this variety:
- Mount Fuji: A symbolic volcano of Japan, it has experienced periods of intense activity for 700.000 years, alternating between periods of explosive eruptions and lava flows.
- Ontake: A volcano whose unexpected eruption in 2014, despite being at alert level 1 (minimum), left dozens of victims and demonstrated the unpredictability of these phenomena.
- Motoshirane and Shinmoedake: Recent examples of volcanoes with changing alerts, whose eruptions have surprised even experts and advanced monitoring systems.
Volcanic activity also includes phenomena such as tsunamis generated by sector collapses, lahars (volcanic mudflows), pyroclastic flows, and gas emissions that affect communities even hundreds of kilometers from the crater.
Volcanic Hazards: Hazards and Management in Japanese Life
Living in Japan means living with the constant risk of eruptions, earthquakes, and other associated phenomena. The risks go far beyond mere physical proximity to an active volcano:
- Volcanic ash: It can cause roof collapses, structural damage, infrastructure obstruction, and affect the respiratory health of the population.
- Lava flows: They generally move slowly, but can destroy homes, crops, and infrastructure in their path.
- Ballistic projectiles: Rock and lava fragments ejected during eruptions can be lethal miles from the crater.
- Lahars and pyroclastic flows: One of the greatest dangers is that they can move at great speeds and wipe out entire towns, even during periods without eruptions if heavy rains move accumulated ash.
- Volcanic gases: Sulfur dioxide (SO₂) in particular can spread over large areas, deteriorating air quality and affecting crops and public health.
The Japan Meteorological Agency monitors more than 50 volcanoes visually and technologically, and updates alerts daily, ranging from level 1 (low) to 5 (mandatory evacuation). This monitoring allows for damage minimization and earlier response, although unpredictability remains a constant: many eruptions have occurred when there was barely any warning.
Iconic examples: Mount Fuji and other historic volcanoes
The figure of Mount Fuji is iconic, but also one of the most studied for its eruptive history and cultural significance. Since its formation on ancient volcanoes (Komitake and Kofuji) more than 700.000 years ago, it has experienced different stages of activity:
- Prehistoric period (700.000 – 200.000 years ago): It sits on the remains of the Komitake volcano.
- Intense eruptions 100.000 years ago: Formation of ancient Fuji and large lava flows.
- Last major eruption (1707): The famous Hōei eruption hurled ash as far away as Tokyo and devastated villages, with lasting social and environmental consequences.
- Recent events: Although there have been no eruptions in centuries, small earthquakes and gas emissions keep the area under surveillance and unrest.
Other relevant active volcanoes:
- Sakurajima: With hundreds of small eruptions each year, it is one of the best-monitored volcanoes in the world and an example of everyday risk.
- Ounces: Responsible for one of the greatest tragedies in recent times, its 1991 eruption left an indelible mark.
- Kusatsu-Shirane, Asama, Iō, Kuchinoerabujima, Suwanosejima and Shinmoedake: All have experienced alert episodes in recent years, with access restrictions or evacuations.
Can earthquakes trigger volcanic eruptions in Japan?
The relationship between earthquakes and eruptions has been the subject of scientific debate for decades. Although one might intuitively think that a large earthquake can "wake up" a volcano, the most recent studies qualify this connection: there is no conclusive evidence that a specific earthquake triggers an immediate eruption, unless the volcano was already close to doing so.
What is observed is a slight increase in the likelihood of eruptive activity in the months or years following a major earthquake, due to the opening of fractures that facilitate the rise of magma. However, most eruptions appear to follow their own internal cycles, something that keeps volcanologists and civil protection agencies on edge.
Risk management: surveillance, local culture and adaptation
Volcanic risk management in Japan is a highly specialized task, combining cutting-edge technology, science, and traditional wisdom. Early warning systems, satellite monitoring, observatories, and collaboration with local communities enable rapid crisis response. Key elements of crisis management include:
- Hazard assessment and geographic models: Hazard maps, scenario simulations, and historical data collection are used to predict potentially affected areas.
- Network of volcanic observatories: With access to real-time data, they enable alerts to be issued and the evacuation of at-risk populations to be coordinated.
- Community involvement: Residents near active volcanoes maintain emergency kits and maintain constant vigilance habits, reinforcing a culture of resilience.
Furthermore, popular and religious knowledge (Shintoism and Buddhism) has generated a peculiar philosophy in the face of disasters: "Shou ga nai" (it can't be helped) is a common expression, reflecting acceptance and adaptation to the inevitable, as well as a search for harmony with nature rather than direct confrontation.
Social, economic and cultural impact of volcanic activity
Volcanism in Japan has left a profound impact on all aspects of local life. From religion to architecture, tourism, customs and the economy, the influence of volcanic activity is palpable:
- Onsen (hot springs): Many of the country's most famous spas, especially in regions like Hakone, exist thanks to the presence of hot springs generated by magmatic activity.
- Hotels and tourist routes: Despite temporary restrictions and closures in areas like Owakudani, most destinations are reopening and welcoming tourists with renewed safety measures.
- Art and iconography: Mount Fuji and other volcanoes have inspired prints, woodcuts, banknotes, literary works, and traditional songs.
- Philosophy of resilience: The recurrence of natural disasters has forged a social spirit based on caution, unity, and resilience in the face of adversity.
On the other hand, the economic damage could be severe, whether due to agricultural losses due to ash, infrastructure damage, mass evacuations, or the temporary halt of tourism and local industry. Even so, Japanese society has managed to reinvent itself, innovating in earthquake-resistant construction, insurance, and disaster response systems.
Case studies: Hakone, Sendai and the creation of new islands
Hakone is one of the most visited volcanic areas by domestic and international tourists, famous for its landscapes and hot springs. When volcanic activity increases, areas like Owakudani can become restricted, impacting mobility and the local economy. However, outside of these at-risk areas, life goes on, and businesses are trying to adapt to maintain their appeal.
The Sendai region was the scene of one of the worst disasters in Japan's recent history in 2011, when an earthquake and subsequent tsunami devastated the eastern coast.. The experience marked a turning point in the local mentality: now, many Japanese stockpile supplies and fuel in anticipation of further disasters and view their daily lives through this prism of uncertainty and constant preparation.
The spontaneous creation of new islands, as recently occurred in Ogasawara, is another notable phenomenon. Although some of these islands are ephemeral and disappear quickly due to erosion, others endure and become part of Japanese territory, representing the dynamic nature of this ever-changing country.
Monitoring and future of volcanic activity in Japan
Japan's future is inextricably linked to its volcanic activity. Constant vigilance thanks to technological advances and international collaboration allows us to be better prepared, but the possibility of surprises is always present. Unexpected eruptions and earthquakes will continue to shape both the landscape and the country's identity.
The Japanese example is paradigmatic: It's not about eliminating risk, but rather learning to live with it, anticipating it, adapting to it, and, to the extent possible, taking advantage of the opportunities offered by this changing environment, such as tourism, science, and technological innovation.
Japan is an example of how nature can shape a country's destiny and, at the same time, inspire its inhabitants to develop a culture of respect, vigilance, and resilience in the face of the challenges the planet poses.