The 3rd TranSEHA Young Researchers Seminar: “Widespread Tephra”

1. Overview
As part of the TranSEHA program’s educational and research exchange activities for early-career researchers and graduate students, the 3rd TranSEHA Young Researchers Seminar, entitled “Widespread Tephra,” was held on June 9–10, 2026. The seminar took place at Daisen Volcano and Shimane University and was designed to provide participants with an understanding of widespread tephra research, from fundamental concepts to practical applications.
A total of 18 participants attended: 10 from TranSEHA (four staff members, three postdoctoral researchers, and three students) and eight from Shimane University (two staff members and six students).
On the first day, participants conducted fieldwork around Daisen Volcano. By observing widespread tephra layers and tephra originating from Daisen Volcano, they deepened their understanding of tephra stratigraphy and the eruptive history of the volcano. On the second day, practical training, lectures, and research presentations were held at Shimane University. Participants learned about methods for processing and microscopically examining tephra samples, as well as research methods and recent findings in widespread tephra studies.

2. Program
(1) Tuesday, June 9, 2026: Field Excursion at Daisen Volcano
Under the guidance of Professor Mitsuru Okuno (Osaka Metropolitan University), Mr. Satoshi Ishiga (Tottori Geological Society), and Associate Professor Andreas Auer (Shimane University), participants visited representative tephra outcrops around Daisen Volcano.
A total of seven sites, including Daisen-ike, Hattori, Kusadanihara, Kagikake-toge, Mitsukue, and Kasarahara, were visited to observe tephra deposits such as the Aira-Tn tephra (AT), Daisen-Kurayoshi Pumice (DKP), and Kirin-Sawa pyroclastic-flow deposits. At each site, explanations were provided regarding tephra facies, methods for regional tephra correlation, and differences in eruption styles, allowing participants to deepen their understanding of volcanic activity and tephra-forming processes.
Participants also observed the morphology of Daisen Volcano from Masumizuhara Plateau (Milk Village) and the Kagikake-toge Observatory, gaining a first-hand appreciation of how dramatically the appearance of the volcano changes depending on the viewing direction.

(2) Wednesday, June 10, 2026: Practical Training and Lectures at Shimane University
The morning session began with an introductory lecture by Professor Okuno entitled “What Is Widespread Tephra?” This was followed by practical training in washing tephra samples and observing them under a microscope. Participants learned basic techniques for identifying tephra, including methods for observing volcanic glass and minerals. Associate Professor Auer then gave a lecture entitled “Petrology of Daisen Volcano,” explaining the magma plumbing system and petrological characteristics of Daisen Volcano.
In the afternoon, Researcher Reona Hiramine (National Museum of Japanese History) gave a presentation entitled “Submarine Volcanoes and Drifting Pumice.” This was followed by research presentations by Erika Vivas Cruz (Master’s student, Shimane University) entitled “Latest Holocene Activity at Daisen Volcano: Insights from Petrography and Geochemistry of Kirin-Sawa Eruption Deposits,” and Arata Ichii (Master’s student, Osaka Metropolitan University) on a magma discharge volume step diagram for the lowermost tephra of the Younger Daisen volcanic deposits. Associate Professor Auer also presented a case study on zircon U–Pb dating of tephra. During the general discussion that followed, participants actively exchanged views on future directions in widespread tephra research and possibilities for collaboration with other research fields.

3. Summary
By combining field observations, sample-processing exercises, microscopic observations, lectures, and research presentations, the seminar provided participants with a systematic opportunity to acquire practical knowledge and skills related to widespread tephra research.
In particular, conducting field observations at Daisen Volcano followed immediately by laboratory exercises at Shimane University enabled participants to experience the entire research process, from observing tephra in the field to analyzing samples in the laboratory. The inclusion of lectures and research presentations in English also made the seminar a valuable opportunity for international academic exchange.
Furthermore, the participation of researchers and students from diverse fields, including space–Earth environmental science, volcanology, geology, and archaeology, contributed significantly to the development of the transdisciplinary research network and early-career researcher training that TranSEHA seeks to promote.

(Masayo Minami)

Day 1: Field Excursion at Daisen Volcano

Day 2: Practical Training and Lectures at Shimane University