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Iwate volcanoIwate volcano is a symmetrical stratovolcano in northern Honshu, Japan, 20 km northwest of Morioka City.
It consists of 2 cones, the older western Nishi-Iwate and the younger eastern summit Higashi-Iwate. The older volcano to the west is truncated by a caldera that resulted from repeated collapse.
The caldera contains a central cone with a 500 m wide crater containing a lake and is breached by a narrow gorge to the NW.
Volcanic activity migrated to the east and built Yakushi-dake, the young, mainly basaltic summit cone of Higashi-Iwate. Yakushi-dake contains a 500 m wide crater and partly buries the eastern rim of the caldera. It is the vent of most recent activity including a lava flow from the eruption in 1732 that traveled down the NE flank.
The last historic activity was a small phreatic eruption from O-jigokudani on the W side of the Onigajo caldera. The eruption caused mudflows.
There are uncertain reports about activity in July 1934.
Background:The western and older volcano Nishi-Iwate contains an oval-shaped 1.8 x 3 km caldera. Nishi-Iwate volcano begin growing about 700,000 years ago and suffered repeated (at least 7) collapse during the past 230,000 years, most recently between 739 and 1615 AD.
1998 magma intrusion event
There was no eruption, but from February to September 1998, dike intrusions were observed geodetically and seismologically at Iwate volcano. Magma commenced rising beneath the eastern basaltic cone and later migrated laterally westward. ...more