About Iwakisan
Iwakisan is a stratovolcano rising to 1,625 meters (5,332 feet) in Japan's Northwestern Pacific Volcanic Regions. Its last known eruption was in 1863 CE. The volcano has produced 20 recorded eruptions, with a maximum Volcanic Explosivity Index (VEI) of 2.
Geography & Climate
Iwakisan is located in Japan, within the Northeast Japan Volcanic Arc of the broader Northwestern Pacific Volcanic Regions. Situated at 40.66° N, 140.30° E in the Northern Hemisphere, the volcano lies within a temperate climate zone. With a summit elevation of 1,625 meters above sea level, Iwakisan is a moderately sized peak that remains accessible to hikers and researchers for much of the year. The volcanic landform is characterized as a composite, which describes the physical shape and structure of the volcanic edifice as observed from the surface.
Geological Context
Iwakisan sits in a subduction zone, where one tectonic plate dives beneath another, creating intense heat and pressure that generates magma. Subduction zones are responsible for many of the world's most explosive volcanoes and deadliest eruptions. For communities in Japan near Iwakisan, this tectonic setting means the volcano is capable of producing powerful explosive eruptions, pyroclastic flows, and lahars that can threaten populated areas within tens of kilometers of the summit. The dominant rock type is andesite / basaltic andesite, a dark, fine-grained volcanic rock that forms from rapidly cooling, low-viscosity lava. Basaltic eruptions tend to be less explosive and produce fluid lava flows that can travel long distances. While less immediately dangerous than explosive eruptions, basaltic lava flows can destroy structures and infrastructure in their path, and volcanic gases released during these eruptions can affect air quality over a wide area.
Eruption History Summary
Iwakisan has 20 recorded eruptions in the geological database, spanning from 1605 CE to 1863 CE. The most powerful recorded event was an explosive event producing ash plumes up to several kilometers in 1856 CE, reaching VEI 2 on the Volcanic Explosivity Index. With an average interval of roughly 13 years between eruptions over a span of 258 years, this is one of the more frequently active volcanoes in the database. This persistent activity suggests a robust and well-supplied magma system beneath the volcano.
Significance
Its 20 recorded eruptions make it one of the most prolific volcanoes in our database, reflecting a persistent and well-documented eruptive history that has provided volcanologists with extensive data for understanding eruption patterns and forecasting future activity.
GVP Reference Summary
Iwakisan volcano, symmetrical on all but its western flanks, has been called the Fujisan of the Tsugaru district. The 2-km-wide summit crater is filled by a lava dome flanked by six explosion craters. Three lava domes are found on the western and southern flanks of the andesitic volcano, the NW-most active volcano in Honshu. Historical eruptions have been reported here since 1600 CE and have consisted primarily of small-to-moderate phreatic explosions.
— Smithsonian Institution, Global Volcanism Program
20 Recorded Eruptions
| Year | VEI | Type | Area |
|---|---|---|---|
| 1863 | 1 | Confirmed Eruption | — |
| 1856 | 2 | Uncertain Eruption | — |
| 1848 | 2 | Uncertain Eruption | — |
| 1845 | 2 | Confirmed Eruption | — |
| 1844 | 2 | Confirmed Eruption | Summit and south flank? |
| 1833 | 2 | Uncertain Eruption | — |
| 1807 | 2 | Uncertain Eruption | — |
| 1800 | 2 | Uncertain Eruption | — |
| 1794 | 2 | Uncertain Eruption | — |
| 1793 | 2 | Uncertain Eruption | — |
| 1790 | 2 | Confirmed Eruption | — |
| 1783 | 2 | Uncertain Eruption | — |
| 1782 | 2 | Uncertain Eruption | South flank |
| 1782 | 2 | Confirmed Eruption | — |
| 1769 | 2 | Uncertain Eruption | — |
| 1709 | 2 | Uncertain Eruption | — |
| 1694 | 2 | Uncertain Eruption | — |
| 1672 | 2 | Uncertain Eruption | — |
| 1618 | 2 | Confirmed Eruption | — |
| 1605 | 2 | Uncertain Eruption | — |
Real-Time Data
USGS Alert Level
Thermal Anomalies
Frequently Asked Questions About Iwakisan
Is Iwakisan an active volcano?+
Iwakisan is classified as active based on credible evidence of past eruptions. Although its last known eruption was in 1863 CE, volcanologists consider it capable of erupting again.
When did Iwakisan last erupt?+
The most recent recorded eruption of Iwakisan occurred in 1863 CE with a Volcanic Explosivity Index (VEI) of 1. The eruption was classified as a "Confirmed Eruption." Iwakisan has 20 recorded eruptions in total.
How high is Iwakisan?+
Iwakisan has a summit elevation of 1,625 meters (5,332 feet) above sea level. At 1,625 meters, it is a moderately sized volcanic peak, roughly comparable to Mount Vesuvius (1,281m).
What type of volcano is Iwakisan?+
Iwakisan is classified as a Stratovolcano. Stratovolcanoes (also called composite volcanoes) are steep, conical volcanoes built up by many layers of hardened lava, tephra, and volcanic ash. They are among the most common and dangerous types, known for explosive eruptions.
Where is Iwakisan located?+
Iwakisan is located in Japan, in the Northwestern Pacific Volcanic Regions. More specifically, it lies within the Northeast Japan Volcanic Arc. Its exact coordinates are 40.656° latitude, 140.303° longitude.
Is it safe to visit Iwakisan?+
Iwakisan can generally be visited, but as with any volcano, visitors should check local conditions and any advisory notices before traveling. Japan may have specific regulations for accessing volcanic areas. Guided tours are often the safest and most informative way to experience a volcano.
