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Mount Iwate

Iwatesan

Complex volcano · Japan · 2038m

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.
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: Photo by Lee Siebert, 1977 (Smithsonian Institution). · Wikimedia Commons
Type
Complex volcano
Country
Japan
Region
Northwestern Pacific / Northeast Japan Volcanic Arc
Elevation
2038m
Coordinates
39.853, 141.001
Last eruption
1919
Tectonic setting
Subduction zone / Continental crust (> 25 km)
Landform
Composite
Major rock type
Basalt / Picro-Basalt
Geological summary

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.

Eruption history

Summary (VEI over time)
Click a bar to see individual eruptions
6450 BCE~6171 BCE · 2 eruptions · max VEI ?5891 BCE~5612 BCE · 1 eruptions · max VEI ?5053 BCE~4773 BCE · 2 eruptions · max VEI ?4494 BCE~4214 BCE · 2 eruptions · max VEI 03935 BCE~3655 BCE · 1 eruptions · max VEI ?3376 BCE~3096 BCE · 1 eruptions · max VEI 03096 BCE~2817 BCE · 2 eruptions · max VEI ?2817 BCE~2537 BCE · 1 eruptions · max VEI ?2258 BCE~1979 BCE · 2 eruptions · max VEI ?1699 BCE~1420 BCE · 2 eruptions · max VEI ?1420 BCE~1140 BCE · 2 eruptions · max VEI 3581 BCE~302 BCE · 2 eruptions · max VEI ?22 BCE~257 · 1 eruptions · max VEI ?1096~1375 · 1 eruptions · max VEI 31375~1655 · 1 eruptions · max VEI ?1655~1934 · 6 eruptions · max VEI 36450 BCE4494 BCE2258 BCE302 BCE1655

Detailed timeline

  1. 1934VEI ?Geological estimate
    1934-07-16 – 1935-07-02
  2. 1919VEI 1Observed
    1919-07-15 – 1919-07-15
    W side of Onigajo caldera (O-jigokudani)
  3. 1732VEI 2Observed
    1732-01-22 – 1732-10
    NE flank of Yakushi-dake
  4. 1689VEI 2Geological estimate
    1689-06-22 – Ongoing
  5. 1687VEI 2Geological estimate
    1687-04-14 – 1687-07
  6. 1686VEI 3Observed
    1686-03-26 – 1686-03-27
  7. 1450 (±100 yrs)VEI ?Geological estimate
    1450 – Ongoing
    Nishi-Iwate and Higashi-Iwate
  8. 1300 (±50 yrs)VEI 3Geological estimate
    1300 – Ongoing
    Higashi-Iwate (Myoko-dake)
  9. 150VEI ?Geological estimate
    150 – Ongoing
    Higashi-Iwate
  10. 350 BCEVEI ?Geological estimate
    BCE 350 – Ongoing
    Higashi-Iwate
  11. 450 BCEVEI ?Geological estimate
    BCE 450 – Ongoing
    Nishi-Iwate (O-jigokudani area)
  12. 1150 BCEVEI ?Geological estimate
    BCE 1150 – Ongoing
    Nishi-Iwate
  13. 1250 BCEVEI 3Geological estimate
    BCE 1250 – Ongoing
    Higashi-Iwate
  14. 1500 BCE (±300 yrs)VEI ?Geological estimate
    BCE 1500 – Ongoing
    Higashi-Iwate
  15. 1650 BCEVEI ?Geological estimate
    BCE 1650 – Ongoing
    Nishi-Iwate (O-jigokudani area)
  16. 2000 BCEVEI ?Geological estimate
    BCE 2000 – Ongoing
    Nishi-yama
  17. 2050 BCE (±200 yrs)VEI ?Geological estimate
    BCE 2050 – Ongoing
    Higashi-Iwate
  18. 2700 BCE (±200 yrs)VEI ?Geological estimate
    BCE 2700 – Ongoing
    Higashi-Iwate
  19. 2950 BCE (±50 yrs)VEI ?Geological estimate
    BCE 2950 – Ongoing
    Nishi-Iwate
  20. 3050 BCEVEI ?Geological estimate
    BCE 3050 – Ongoing
    Higashi-Iwate
  21. 3250 BCE (±500 yrs)VEI 0Geological estimate
    BCE 3250 – Ongoing
  22. 3750 BCE (±100 yrs)VEI ?Geological estimate
    BCE 3750 – Ongoing
    Higashi-Iwate
  23. 4350 BCE (±500 yrs)VEI ?Geological estimate
    BCE 4350 – Ongoing
    Higashi-Iwate
  24. 4450 BCE (±500 yrs)VEI 0Geological estimate
    BCE 4450 – Ongoing
    Higashi-Iwate
  25. 4850 BCE (±50 yrs)VEI ?Geological estimate
    BCE 4850 – Ongoing
    Nishi-Iwate
  26. 4900 BCE (±100 yrs)VEI ?Geological estimate
    BCE 4900 – Ongoing
    Higashi-Iwate
  27. 5650 BCE (±50 yrs)VEI ?Geological estimate
    BCE 5650 – Ongoing
    Nishi-Iwate
  28. 6300 BCE (±100 yrs)VEI ?Geological estimate
    BCE 6300 – Ongoing
    Nishi-Iwate
  29. 6450 BCE (±1600 yrs)VEI ?Geological estimate
    BCE 6450 – Ongoing

External links

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