Asian Consortium of Volcanology
The 5th Field CampMarch 13th – 16th , 2023
Izu-Oshima volcano, Japan1

ACV member organizations
Earth Observatory of Singapore,
Nanyang Technological University, Singapore

Centre for Volcanology and Geological
Hazard Mitigation, Indonesia
Philippine Institute of Volcanology andSeismology, Philippine

China Earthquake Administration, China

Taiwan Volcano Observatory-Tatun, Taiwan

The University of Hong Kong, Hong Kong
Volcano Specialized Research Center,South Korea

National Research Institute for Earth Scienceand Disaster Resilience, Japan2

Program
ACV-FC5 Program
12/03 (Sun), 2023: Arrival at Tokyo via Haneda / Narita airport
13/03 (Mon), 2023: DAY1
07:45 Meet at Tokyo Takeshiba Terminal (Port)
08:35 Departure from Takeshiba (Jetfoil)
10:40 Arrival at Izu-Oshima (Okada / Motomachi Port)
11:00 Check-in at Oshima Onsen Hotel
11:30 Opening ceremony
12:00 Lunch
13:00 Lecture 1: Outline of Izu-Oshima volcano (Eisuke)
14:00 Lecture 2: Izu-Oshima eruption: Observations and Models (Tomo)
15:00 Poster session
17:00 end
14/03 (Tue), 2023: DAY2
10:30 Lecture 3: Petrology (Takahiro)
12:00 Lunch
13:00 Lecture 4: Dynamics of dike intrusion (Yosuke)
14:00 Lecture 5: Seismic analysis (Takashi)
15:00 Poster Session
17:00 end
15/03 (Wed), 2023: DAY3
08:15-17:30 Field trip
16/03 (Thu), 2023: DAY4
09:00 Lecture 6: Hazard & Counter measures (Susanna & Christina)
11:30 Closing ceremony
12:00 Lunch
13:30 Moving to Port
15:10 Departure from Izu-Oshima (Okada / Motomachi Port; by Jetfoil)
17:35 Arrival at Tokyo (Takeshiba)
Hotel in Tokyo
17/03 (Fri), 2023: Departure from Haneda / Narita
3

Field trip (March 15th)
8:15

Departure at Oshima Onsen hotel

8:30

Gojinkajaya [2][1]

Field trip around Summit crater and caldera(Stop 1-3)

[3]

14:00 Gojinkajaya
14:30-15:30 Izu-Oshima Museum of Volcanoes(Stop 4)[3]
[4]

15:40-16:00 Stratum Section [4] (Stop 5)
16:20-16:50 Habu area (Maar)[5] (Stop 6)

17:30 Arrival at Oshima Onsen hotel

4

Field guide of Izu Oshima volcano for ACV-FC5
Yoshihisa Kawanabe (GSJ)
Stop 1 View of the caldera from the Oshima Onsen Hotel and fall-out deposits of the Younger Oshima
GroupWe can see the summit caldera and the central cone, Miharayama and several lava flows such as 1986 B lava flows(LB-I, -II, -III). In the car parking, tephra layers of the Younger Oshima Group can be seen. Thin white rhyolite ashlayer, belongs to N3 unit of the Younger Oshima Group, is an exotic ash from southwestern Tenjosan volcano inKozushima island erupted in 9th century.
Stop 2 Gojinka-jaya
Gojinka-jaya is a lookout on the NW rim of the caldera of the Izu-Oshima volcano. Miharayama, a central cone,lies just in front of us beyond the caldera floor and 1950-51 and 1986 lava flows spilled out from the Miharayama
summit crater are seen. A ridge to the left of the cone is the spatter rampart along the B fissure of the 1986 eruption.
The hummocky low mounds in the foreground of the B fissure are the vent area of the 1777-1778 lava flow.
Stop 3 Field trip around Summit crater and caldera
Along the new trail climbing up to the Miharayama, we can see many driblets of the cone forming eruption in
1777-1778. The ejecta is divided into three units based on plagioclase phenocryst volume and grain size, two of
which can be observed (Ikenaga et al., 2018). At the last sharp bend of the trail, we can see the successions of theerupted materials after 1778. The surge deposits cover the driblets, and then thin layers of scoria and Pele’s hair,
which is the earliest ejecta of the 1986 eruption, cover them and 1986 A lava flow and 1986 B scoria overlie them.
The trail ends at the viewing site near the pit crater of the Miharayama. Diameter of the pit is about 350 m and thedepth is about 100-150 m. The same sized pit had been existed before the 1986 eruption, and it filled up by thelava from 1986 A vent and formed lava lake. On Nov. 16, 1987, a large explosion happened with a rapid
withdrawal of magmas back to the conduit, and the pit crater was regenerated.
From the path circling the crater of Miharayama, we can see other Izu volcanic islands, the Izu Peninsula, andMt.Fuji volcano. To the east of Miharayama is a black "desert" with almost no vegetation. Large craters of the1986 B fissure is located on the outer side of the northern margin of Miharayama crater and the B lava flows fromthe 1986 B fissure can be seen.
Stop 4 Izu-Oshima Museum of Volcanoes
The Izu-Oshima Museum of Volcanoes opened in 1990 exhibits the details of the 1986 eruption and growth historyof Izu-Oshima volcano together with much information about volcanoes. The museum is currently considering
renewal in order to update the exhibits and make it a center for Geopark activities.
Stop 5 “The Great Road Cut” of the fallout deposits of the Izu-Oshima volcano
We can see the spectacular exposure of the many alterations of air-fall scoria and ash, divided by weathered ash,and several lava flows between the fallout deposits. Each sequence of scoria, ash and weathered ash correspond tothe one eruptive period. The thick scoria deposit (O95) fell about 16000-17000 years ago (Suzuki and Usui, 2022).
There are some unconformities where the upper strata obliquely truncate the lower strata. At the uppermost area ofthe outcrop, we can see the S2 flow deposit and bomb sag which were generated by the large phreatic eruption
occurred at the summit about 1700 years ago.
Stop 6 Habu-minato crater
The Habu-minato crater is an explosion crater. The explosion breccia and surge deposit distribute around the crater.
This breccia belongs to N3 unit of the Younger Oshima Group and intercalates adventitious white rhyolite ash fromsouthwestern rhyolite volcanoes erupted in 9th century. The crater is 400 m in diameter. In 1703, large tsunami
broke the southern rim of the Habu-minato crater and connected to the sea. After that, residents have been used asa fishing port by dredging the waterway.
5

ParticipantsName

Affiliation

NationSusanna JENKINSEOSSingaporeChristina WIDIWIJAYANTI

EOSSingapore

Yizhou LUO

EOSSingapore

Eleanor Mary TENNANT

EOS

Singapore

Andika Bayu AJI

EOSSingapore

Oktory PRAMBADA

CVGHM

Indonesia

Ahmad BASUKI

CVGHM

Indonesia

Valerie Shayne Vargas OLFINDOPHIVOLCS

Philippine

James Noli Villarete NOBORAPHIVOLCS

Philippine

Jude Lorica MALLORCAPHIVOLCS

Philippine

Wen-Jian YANG

CEA

China

Lili YAN

CEA

China

Ya-Chuan LAI

TVO

TaiwanYu-jen CHANG

Yangmingshan N.P.

TaiwanHuai-yu TANG
Sung-Hyo YUN

Taiwan U.

TaiwanPusan U.

South Korea

Cheolwoo CHANG

Pusan U.

South KoreaJeongheon JU

Pusan U.

South Korea

Eunjeong YANG

Pusan U.

South Korea

Eisuke FUJITANIEDJapan

Tomofumi KOZONONIEDJapan

Takahiro MIWA

NIEDJapan

Takashi HIROSENIEDJapan

Yosuke AOKIERI, U. TokyoJapan

Yoshihisa KAWANABE

GSJ, AISTJapan

Kurumi IWAHASHIERI, U. Tokyo

Japan

Ryohei KIKUCHI

Kobe U.

Japan

Sora NISHIKAWA

Hokkaido U.

Japan

Asami HONDATokyo I. of Tech.

Japan

Wakako NUMATA

Toyama U.

Japan6