Omanago Group

Lava dome(s) in Japan

Last Eruption: -3050

Key Facts

Elevation

2,341 m (7,680 ft)

Type

Lava dome(s)

Location

36.807°, 139.476°

Region

Northeast Japan Volcanic Arc

Rock Type

Dacite

Tectonic Setting

Subduction zone

Location

Loading map...

Overview

The Omanago volcano group consists of a series of five closely spaced lava domes that were constructed north and NW of Nantai volcano in Nikko National Park. The highest of the dacitic domes is Omanago, which later erupted andesitic lavas. The Mitsudake dome, which overlooks the hot spring resort of Lake Yunoko, was radiocarbon dated at about 5,000 years ago.

Mitsudake was constructed on a southerly dipping slope, so that the southern of its two flat-topped domes is lower, and is overlapped by sediments of the Senjogahara plain.

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	5076 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: 283142
•Evidence: Eruption Dated
•Epoch: Holocene

About the Photo

The Omanago volcano group (upper left) consists of a series of five lava domes in Nikko National Park. The highest dome is Omanago, located at the SE end of the complex. Mitsudake is the NW-most dome. The higher northern peak of the Mitsudake complex is out of view to the left, and the lower southern dome forms the low ridge behind the hot spring resort of Yunoko lake in the center of the photo. The peak on the right horizon is Nantaisan.

Photo by Lee Siebert, 1964 (Smithsonian Institution).