Toshima

Stratovolcano in Japan

Last Eruption: -4550

Key Facts

Elevation

508 m (1,667 ft)

Type

Stratovolcano

Location

34.520°, 139.279°

Region

Izu Volcanic Arc

Rock Type

Basalt / Picro-Basalt

Tectonic Setting

Subduction zone

Location

Loading map...

Overview

The small 2 x 2. 4 km island of Toshima is located in the northern Izu Islands south of Izu-Oshima Island about 20 km W of the main volcanic front. Steep cliffs up to 300 m high ring the basaltic to basaltic andesite island on three sides.

The summit is asymmetrically located opposite the more gentle slopes of the northern side of the island, where the village of Toshima is located. The latest known eruption of this stratovolcano occurred sometime between about 9,000 and 4,000 years ago, producing a lava flow from Kajiana crater.

Volcanic Hazards & Risk Assessment

Primary Hazards

Pyroclastic flows
Lava flows
Volcanic bombs and ballistics
Lahars and mudflows

Risk Level

Population at RiskHigh

Infrastructure RiskModerate

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 Dated

Eruption Statistics & Analysis

Metric	Value	Global Ranking	Significance
Total Recorded Eruptions	Unknown	Low	Moderately active volcano
Maximum VEI	VEI Unknown	Minor	Local impact potential
Recent Activity	6576 years ago	Historical	Historically 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: 284011
•Evidence: Eruption Dated
•Epoch: Holocene

About the Photo

Steep cliffs up to 300-m-high surround the small island of Toshima. Toshimamura, the port village of the island, is to the far left in this view from the west. Toshima lies about 20 km W of the main volcanic front of the Izu-Marianas arc. Recent activity occurred between about 8,000 and 40,00 years ago.

Copyrighted photo by Shun Nakano (Japanese Quaternary Volcanoes database, RIODB, http://riodb02.ibase.aist.go.jp/strata/VOL_JP/EN/index.htm and Geol Surv Japan, AIST, http://www.gsj.jp/).