Ioto
Caldera in Japan
Key Facts
Elevation
169 m (554 ft)
Type
Caldera
Location
24.751°, 141.289°
Region
Ogasawara Volcanic Arc
Total Eruptions
27
Max VEI
VEI 1
Rock Type
Trachyandesite / Basaltic Trachyandesite
Tectonic Setting
Subduction zone
Location
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Eruption Timeline
Most recent confirmed eruption
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Overview
Ioto, in the Volcano Islands of Japan, lies within a 9-km-wide submarine caldera. The volcano is also known as Ogasawara-Iojima to distinguish it from several other "Sulfur Island" volcanoes in Japan. The triangular, low-elevation, 8-km-long island narrows toward its SW tip and has produced trachyandesitic and trachytic rocks that are more alkalic than those of other volcanoes in this arc.
The island has undergone uplift for at least the past 700 years, accompanying resurgent doming of the caldera; a shoreline landed upon by Captain Cook's surveying crew in 1779 is now 40 m above sea level. The Motoyama plateau on the NE half of the island consists of submarine tuffs overlain by coral deposits and forms the island's high point. Many fumaroles are oriented along a NE-SW zone cutting through Motoyama.
Numerous recorded phreatic eruptions, many from vents on the W and NW sides of the island, have accompanied the uplift.
Volcanic Hazards & Risk Assessment
Primary Hazards
- Pyroclastic flows and surges
- Large explosive eruptions (VEI 4+)
- Ash fall and tephra deposits
- Lahars and debris flows
Risk Level
Geological Composition & Structure
Rock Types
Tectonic Setting
Age & Formation
Eruption Statistics & Analysis
| Metric | Value | Global Ranking | Significance |
|---|---|---|---|
| Total Recorded Eruptions | 27 | High | Highly active volcano |
| Maximum VEI | VEI 1 | Minor | Local impact potential |
| Recent Activity | 1 years ago | Very Recent | Currently active |
Monitoring & Alert Status
Monitoring Networks
Current Status
Nearby Volcanoes in Northwestern Pacific Volcanic Regions
Quick Info
- •Smithsonian ID: 284120
- •Evidence: Eruption Observed
- •Epoch: Holocene
About the Photo
The discolored water seen here is from the September 2001 Ioto submarine eruption, with the vent marked by the yellow arrow. The island is located within a 9-km-wide submarine caldera and narrows toward its SW tip, where the Suribachiyama cone is located. Numerous phreatic eruptions and uplift over at least the past 700 years has accompanied resurgent doming of the caldera.
Photo by Nakahori, 2001 (Japan Meteorological Agency, published in the Bulletin of the Global Volcanism Network).
Authority Sources
Related Volcanoes
Basic Information
This page shows basic data from the Smithsonian Global Volcanism Program. For more detailed information, visit the official Smithsonian page.