Kozushima

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  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 34.219°N
  • 139.153°E

  • 572 m
    1876 ft

  • 284030
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number

The Global Volcanism Program has no activity reports for Kozushima.

The Global Volcanism Program has no Weekly Reports available for Kozushima.

Index of Monthly Reports

Reports are organized chronologically and indexed below by Month/Year (Publication Volume:Number), and include a one-line summary. Click on the index link or scroll down to read the reports.

04/1991 (BGVN 16:04) Earthquake swarm but no surface activity

10/1991 (BGVN 16:10) Earthquake swarm N of island

01/1992 (BGVN 17:01) Earthquake swarm follows nearby Nii-jima seismicity; no surface activity observed

04/1992 (BGVN 17:04) Two seismic swarms; no surface changes evident

05/1992 (BGVN 17:05) Continued seismic swarms

06/1992 (BGVN 17:06) Earthquake and aftershocks

08/1992 (BGVN 17:08) Weak seismic swarm; surface activity unchanged

09/1992 (BGVN 17:09) Weak earthquake swarm

10/1992 (BGVN 17:10) Earthquake swarm but no surface changes evident

03/1993 (BGVN 18:03) Earthquake swarm on 25 March; no surface anomalies

08/1993 (BGVN 18:08) Earthquake swarms

09/1995 (BGVN 20:09) Strong earthquake swarm in early October

10/1995 (BGVN 20:10) Earthquake swarm ends in mid-October


Contents of Monthly Reports

All information contained in these reports is preliminary and subject to change.

All times are local (= UTC + 9 hours)

04/1991 (BGVN 16:04) Earthquake swarm but no surface activity

An earthquake swarm (M <= 4.0) occurred from 2100 to 2400 on 23 April, with seismicity gradually returning to normal levels by the following day. Many of the earthquakes were felt by residents (to JMA intensity IV). Swarm events were centered from the W coast to 20 km SW of the island (figure 1), at 0-10 km depth. No surface activity was reported.

Figure 1. Epicenter map (top) and space/time diagram (bottom) showing seismicity around Kozu-shima and Nii-jima volcanoes, January 1991-June 1992. Courtesy of JMA.

Information Contact: JMA.

10/1991 (BGVN 16:10) Earthquake swarm N of island

An earthquake swarm occurred 24-25 October in the sea 7 km N of Kozu-shima (figure 1). The largest shocks (M 4.9) were recorded at 1746 and 1754 on the 24th. Changes in surface activity were not observed on the island or in the epicentral area. The seismicity was the first for the area since 23 April . . . .

Information Contact: JMA.

01/1992 (BGVN 17:01) Earthquake swarm follows nearby Nii-jima seismicity; no surface activity observed

On 26-27 January, three weeks after an earthquake swarm centered ~10 km NE of the volcano, another swarm was recorded a few kilometers E of Kozu-shima (figure 1). The 26-27 January swarm's two largest shocks, M 3.3, occurred at 2041 and 2050 on the 26th. No surface activity was observed.

Information Contact: JMA.

04/1992 (BGVN 17:04) Two seismic swarms; no surface changes evident

A seismic swarm occurred 21-25 April, centered a few kilometers NW of the island. Some of the shocks were felt by island residents; the largest, M 3.6, occurred on 23 April. Another swarm was recorded on 8 May, centered E of the island (maximum M 3.9). No surface anomalies were observed.

Information Contact: JMA.

05/1992 (BGVN 17:05) Continued seismic swarms

Abnormal seismicity continued around the volcano in May, when 2 earthquake swarms were recorded. On 8 May a swarm occurred 2-3 km E of the island, with M <3.9. The second, on 14-16 May, occurred 3-4 km NW, with the largest event (M 4.9) recorded at 0731 on 15 May. No surface anomalies were observed.

Information Contact: JMA.

06/1992 (BGVN 17:06) Earthquake and aftershocks

A M 5.2 earthquake, centered in the sea 8 km SW of the volcano at 9 km depth, occurred on 15 June at 1046. Island residents felt the shock at intensity 5 on the JMA scale of 0-7. Data from 30 stations of the Worldwide Standardized Seismic Network yielded magnitudes of 4.9 (mb) and 4.7 (Ms). One person was slightly injured by a rockfall, and wallrock collapse at 10 sites closed 5 roads to traffic. Aftershocks continued until 17 June off the island's SW coast. The event was the second largest since . . . April 1991 (figure 1). No surface anomalies were observed on the island or on the sea-surface nearby.

Information Contacts: JMA; NEIC.

08/1992 (BGVN 17:08) Weak seismic swarm; surface activity unchanged

A weak earthquake swarm was detected 5 km NE of the volcano island on 18 August. Maximum magnitude was 3.0. No surface activity was evident on the island or in the sea.

Information Contact: JMA.

09/1992 (BGVN 17:09) Weak earthquake swarm

A weak earthquake swarm occurred 5 km W of the island on 1 September. Maximum magnitude was 2.1. No surface activity was evident on the island or in the sea.

Information Contact: JMA.

10/1992 (BGVN 17:10) Earthquake swarm but no surface changes evident

A swarm of earthquakes occurred midway between [Nii-jima and Kozu-shima] islands 17-20 October. The largest earthquake was M 5.1, at 2237 on 17 October. No ocean-surface anomalies were observed.

Information Contact: JMA.

03/1993 (BGVN 18:03) Earthquake swarm on 25 March; no surface anomalies

. . . On 25 March, a swarm occurred at Kozu-shima island, ~20 km SW of Nii-jima. The largest event was M 3.9. No surface anomalies, onshore or offshore, were observed . . . .

Information Contact: JMA.

08/1993 (BGVN 18:08) Earthquake swarms

An earthquake swarm near and below Kozu-shima island occurred on 9-10 August, with 12 shocks felt on the island, the largest M 3.3. Another earthquake near the island, M 3.7, occurred in the early morning on 22 August.

Information Contact: JMA.

09/1995 (BGVN 20:09) Strong earthquake swarm in early October

At 2143 on 6 October, a M 5.6 earthquake occurred near Kozu-shima (figure 2). The earthquake, which had an intensity at Kozu-shima of V on JMA's scale, caused a few landslides there. A M 4.8 earthquake 14 minutes earlier had an intensity of IV. During the next several days, an earthquake swarm continued offshore to the SW of Kozu-shima (figure 2, bottom). The swarm's maximum depth shifted downward with time, reaching 20-25 km. None of this seismicity was thought to have been induced by volcanism.

Figure 2. Kozu-shima epicenter map (top) and plot of focal depths versus time for September through 16 October 1995 (bottom). Courtesy of JMA.

Though obscured by epicenters on figure 2, Kozu-shima island has dimensions of 4 x 6 km and lies 20 km SSW of Nii-jima island and adjacent to the Izu Peninsula. Kozu-shima contains abundant rhyolitic surge deposits and lava domes. Its last eruption was in 838-840 AD. Seismicity near the volcano, and sometimes in vicinity of Nii-jima, has been episodically high in recent years.

Information Contact: Volcanological Division, Seismological and Volcanological Department, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100 Japan.

10/1995 (BGVN 20:10) Earthquake swarm ends in mid-October

As reported in BGVN 20:09, on 6 October a M 5.6 earthquake occurred adjacent to Kozu-shima and a seismic swarm followed for the next few days. After that, seismic events continued but decreased toward the end of October; in total, during October there were 246 felt earthquakes.

Information Contact: Volcanological Division, Seismological and Volcanological Department, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100 Japan.

A cluster of rhyolitic lava domes and associated pyroclastic deposits form the small 4 x 6 km island of Kozushima in the northern Izu Islands. Kozushima lies along the Zenisu Ridge, one of several en-echelon ridges oriented NE-SW, transverse to the trend of the northern Izu arc. The youngest and largest of the 18 lava domes, 574-m-high Tenjoyama, occupies the central portion of the island. Most of the older domes, some of which are Holocene in age, flank Tenjoyama to the north, although late-Pleistocene domes are also found at the southern end of the island. Only two possible historical eruptions, from the 9th century, are known. A lava flow may have reached the sea during an eruption in 832 CE. Tenjosan lava dome was formed during a major eruption in 838 CE that also produced pyroclastic flows and surges. Earthquake swarms took place during the 20th century.

Summary of Holocene eruption dates and Volcanic Explosivity Indices (VEI).

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
0838 Aug 2 (?) Unknown Confirmed 4 Historical Observations Tenjo-san
[ 0832 ] [ Unknown ] Uncertain    
0100 BCE ± 950 years Unknown Confirmed   Hydration Rind NW tip of island (Kobe-yama)
0750 BCE ± 700 years Unknown Confirmed   Hydration Rind N tip of island (Anano-yama, Hanatabe)
8050 BCE (?) Unknown Confirmed   Tephrochronology Jogo-yama

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.



Synonyms
Kozu-sima | Kozu-shima


Domes
Feature Name Feature Type Elevation Latitude Longitude
Anano-yama
    Anagi-yama
Dome
Hanatate Dome
Jogo-yama
    Zyogoro-yama
Dome
Kobe-yama Dome 270 m
Matsuyamahana Dome
Osawa Dome
Takado-yama Dome 304 m
Tenjo-san
    Tenzyo-san
Dome 574 m 34° 12' 58" N 139° 9' 23" E
Tenjo lava dome, in the central part of the island of Kozu-shima, was formed during the most recent eruption of the volcano in 838 AD. Formation of the rhyolitic lava dome was accompanied by pyroclastic flows and surges and the extrusion of flow-banded lava flows.

Photo by Ichio Moriya (Kanazawa University).
The cultivated floor of an explosion crater (left) and a flat-topped lava dome (right) are part of Kozu-shima volcano in the northern Izu Islands. The small 4 x 6 km island is formed by a cluster of rhyolitic lava domes and associated pyroclastic deposits. The youngest and largest dome, 574-m-high Tenjo-yama, occupies the central portion of the island. Most of the older domes flank Tenjo-yama on the north. Only two historical eruptions, from the 9th century, are known.

Photo by Ichio Moriya (Kanazawa University).

The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title.

Japan Meteorological Agency, 1996. National Catalogue of the Active Volcanoes in Japan (second edition). Tokyo: Japan Meteorological Agency, 502 p (in Japanese).

Japan Meteorological Agency, 2013. National Catalogue of the Active Volcanoes in Japan (fourth edition, English version). Japan Meteorological Agency.

Kudo T, Hoshizumi H, 2006-. Catalog of eruptive events within the last 10,000 years in Japan, database of Japanese active volcanoes. Geol Surv Japan, AIST, http://riodb02.ibase.aist.go.jp/db099/eruption/index.html.

Kuno H, 1962. Japan, Taiwan and Marianas. Catalog of Active Volcanoes of the World and Solfatara Fields, Rome: IAVCEI, 11: 1-332.

Nakano S, Yamamoto T, Iwaya T, Itoh J, Takada A, 2001-. Quaternary Volcanoes of Japan. Geol Surv Japan, AIST, http://www.aist.go.jp/RIODB/strata/VOL_JP/.

Noguchi S, Toramaru A, Shimano T, 2006. Crystallization of microlites and degassing during magma assent: constraints on the fluid mechanical behavior of magma during the Tenjo eruption on Kozu Island, Japan. Bull Volc, 68: 432-449.

Suga K, Miyazaki Y, Chigira M, Endo K, Murakami H, 2003. Age of Takodoyama volcano, Kozushima, Izu Islands. Bull Volc Soc Japan (Kazan), 48: 499-505 (in Japanese with English abs).

Tsukui M, Saito K, Hayashi K, 2006. Frequent and intensive eruptions in the 9th century, Izu Islands, Japan: revision of volcano-stratigraphy based on tephras and historical documents. Bull Volc Soc Japan (Kazan), 51: 327-338 (in Japanese with English abs).

Yokoyama T, Shimada A, Umemura T, Toyoda S, 2004. ESR ages of rhyolitic monogenetic volcanoes in Kozushima, Japan. Bull Volc Soc Japan (Kazan), 49: 23-32 (in Japanese with English abs).

Volcano Types

Lava dome(s)

Tectonic Setting

Subduction zone
Oceanic crust (< 15 km)

Rock Types

Major
Rhyolite

Population

Within 5 km
Within 10 km
Within 30 km
Within 100 km
2,406
2,406
5,716
442,731

Affiliated Databases

Large Eruptions of Kozushima Information about large Quaternary eruptions (VEI >= 4) is cataloged in the Large Magnitude Explosive Volcanic Eruptions (LaMEVE) database of the Volcano Global Risk Identification and Analysis Project (VOGRIPA).
WOVOdat WOVOdat is a database of volcanic unrest; instrumentally and visually recorded changes in seismicity, ground deformation, gas emission, and other parameters from their normal baselines. It is sponsored by the World Organization of Volcano Observatories (WOVO) and presently hosted at the Earth Observatory of Singapore.
EarthChem EarthChem develops and maintains databases, software, and services that support the preservation, discovery, access and analysis of geochemical data, and facilitate their integration with the broad array of other available earth science parameters. EarthChem is operated by a joint team of disciplinary scientists, data scientists, data managers and information technology developers who are part of the NSF-funded data facility Integrated Earth Data Applications (IEDA). IEDA is a collaborative effort of EarthChem and the Marine Geoscience Data System (MGDS).
Smithsonian Collections Search the Smithsonian's NMNH Department of Mineral Sciences collections database. Go to the "Search Rocks and Ores" tab and use the Volcano Name drop-down to find samples.