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Iwatesan

Complex in Japan

Last Eruption: 1919

Key Facts

Elevation

2,038 m (6,686 ft)

Type

Complex

Location

39.853°, 141.001°

Region

Northeast Japan Volcanic Arc

Rock Type

Basalt / Picro-Basalt

Tectonic Setting

Subduction zone

Location

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Overview

Viewed from the east, Iwatesan volcano has a symmetrical profile that invites comparison with Fuji, but on the west an older cone is visible containing an oval-shaped, 1. 8 x 3 km caldera. After the growth of Nishi-Iwate volcano beginning about 700,000 years ago, activity migrated eastward to form Higashi-Iwate volcano.

Iwate has collapsed seven times during the past 230,000 years, most recently between 739 and 1615 CE. The dominantly basaltic summit cone of Higashi-Iwate volcano, Yakushidake, is truncated by a 500-m-wide crater. It rises well above and buries the eastern rim of the caldera, which is breached by a narrow gorge on the NW.

A central cone containing a 500-m-wide crater partially filled by a lake is located in the center of the oval-shaped caldera. A young lava flow from Yakushidake descended into the caldera, and a fresh-looking lava flow from the 1732 eruption traveled down the NE flank.

Volcanic Hazards & Risk Assessment

Primary Hazards

    Risk Level

    Population at RiskHigh
    Infrastructure RiskHigh
    Aviation RiskSignificant

    Geological Composition & Structure

    Rock Types

    Primary
    Basalt / Picro-Basalt
    Silica Content
    Low (45-52% SiO₂)

    Tectonic Setting

    Subduction zone
    Formed by oceanic plate subduction, typically producing explosive eruptions due to water-rich magmas.

    Age & Formation

    Epoch
    Holocene
    Evidence
    Eruption Observed

    Eruption Statistics & Analysis

    MetricValueGlobal RankingSignificance
    Total Recorded EruptionsUnknownLowModerately active volcano
    Maximum VEIVEI UnknownMinorLocal impact potential
    Recent Activity107 years agoHistoricalHistorically active

    Monitoring & Alert Status

    Monitoring Networks

    Japan Meteorological Agency (JMA)
    Real-time seismic monitoring
    Geological Survey of Japan
    Geochemical monitoring
    Global Volcanism Program
    International eruption database

    Current Status

    Normal
    No recent activity. Routine monitoring continues.

    Nearby Volcanoes in Northwestern Pacific Volcanic Regions

    Regional Volcanic Activity
    The Northwestern Pacific Volcanic Regions contains multiple active volcanic systems. Cross-regional magma interactions and tectonic stresses can influence eruption patterns across the entire arc. Monitor regional seismic activity and volcanic alerts.

    Quick Info

    • •Smithsonian ID: 283240
    • •Evidence: Eruption Observed
    • •Epoch: Holocene

    About the Photo

    Yakushidake (right) forms the summit of Iwatesan, and is a younger cone that was constructed over the eastern rim of NishiIwate caldera, the left-hand peak in this view from the SE. Eruptions have been recorded since the 17th century, mostly from the 500-m-wide summit crater and flank vents.

    Photo by Lee Siebert, 1977 (Smithsonian Institution).

    Authority Sources

    Smithsonian GVP
    Official volcano database
    JMA Volcano Info
    Japan Meteorological Agency
    GSJ Volcano Database
    Geological Survey of Japan
    USGS Volcano Hazards
    U.S. Geological Survey
    Global Volcanism Program
    Smithsonian Institution

    Related Volcanoes

    In Japan:
    All Japan Volcanoes
    105 active volcanoes
    By Type:
    Caldera Volcanoes
    Large collapse features
    By Region:
    Kuril Volcanic Arc
    Subduction zone volcanoes

    Basic Information

    This page shows basic data from the Smithsonian Global Volcanism Program. For more detailed information, visit the official Smithsonian page.