Numazawa

Shield in Japan

Last Eruption: -3400

Key Facts

Elevation

835 m (2,740 ft)

Type

Shield

Location

37.444°, 139.566°

Region

Northeast Japan Volcanic Arc

Rock Type

Dacite

Tectonic Setting

Subduction zone

Location

Loading map...

Overview

Numazawa is a small, 2-km-wide dominantly dacitic-to-rhyolitic caldera constructed within an older Pliocene caldera. Eruptions of the 110,00 years before present (BP) rhyolitic Shibahara pyroclastic-fall deposit and the 71,000 BP dacitic Mukuresawa lava dome were followed by the dacitic plinian Mizunuma eruption about 45,000 BP, emplacement of the Sozan lava dome at 43,000 BP and the Sozan lava dome at about 20,000 BP. The Numazawako pumice flow and plinian eruption about 4600 years BP resulted in formation of the 1.

5 x 2 km Numazawako caldera, now largely filled by a caldera lake.

Volcanic Hazards & Risk Assessment

Primary Hazards

Risk Level

Population at RiskHigh

Infrastructure RiskModerate

Aviation RiskSignificant

Geological Composition & Structure

Rock Types

Primary

Dacite

Silica Content

Varied composition

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	5426 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: 283151
•Evidence: Eruption Dated
•Epoch: Holocene

About the Photo

Numazawa caldera lake is viewed from its NE shore with a 40,000-year-old lava dome forming the right horizon. The 1.5 x 2 km caldera was formed about 5,000 years ago during the eruption of the Numazawako Pumice Flow and Plinian fall deposit. The small Numazawa caldera was constructed within an older Pliocene caldera.

Copyrighted photo by Tadahide Ui (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/).