Naruko

Caldera in Japan

Last Eruption: 837

Key Facts

Elevation

470 m (1,542 ft)

Type

Caldera

Location

38.729°, 140.734°

Region

Northeast Japan Volcanic Arc

Rock Type

Rhyolite

Tectonic Setting

Subduction zone

Location

Loading map...

Overview

Naruko is a poorly defined, 5. 5 x 7 km caldera NW of the city of Sendai. Formed during eruptions about 73,000 and 45,000 years ago, it contains a cluster of four dacitic lava domes of Holocene age surrounding the 400-m-wide lake-filled Katanuma crater.

The highest of the low, but steep-sided lava domes, Ogadake, lies SE of the lake and reaches only 470 m above sea level. Ogadake and Kurumigadake domes are capped by conglomerates and mudstones uplifted during dome growth. The only recorded eruption in occurred in 837 CE.

Water vapor and sulfur-dioxide gas emission occurs from Shurado crater on Toyagamori lava dome west of the lake and from the bottom of the crater lake, which is one of the most acidic in Japan, with a pH of 1. 6. Solfataras are found on the western shore of Katanuma, and sulfur is mined from sediments on the lake floor.

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

Population at RiskHigh

Infrastructure RiskModerate

Aviation RiskSignificant

Geological Composition & Structure

Rock Types

Primary

Rhyolite

Silica Content

High (>68% 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 Observed

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	1189 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: 283200
•Evidence: Eruption Observed
•Epoch: Holocene

About the Photo

Katanuma lake in the 5.5 x 7 km Narugo caldera is seen from its NW shore with Ogadake lava dome on the right-center horizon. It is the highest of a cluster of lava domes surrounding the lake at 470 m above sea level. Katanuma is one of the most acidic crater lakes in Japan, with a pH of 1.6, and sulfur is mined from sediments on the lake floor.

Copyrighted photo by Jun'ichi Itoh (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/).