The Japanese Islands are a region where volcanoes cluster. As seen in Figure 1, active volcanoes, however, do not exist all over Japan but their distribution is partial. The edge of the distribution on the Pacific side is called volcanic front that runs almost parallel to the Kurile, Japan and Izu-Ogasawara Trench, along which the Pacific plate is subducting beneath the continental plate.

There are many volcanoes along the volcanic front, a few of them appear in the west (Japan Sea) side, but none is seen in the east of the trench. Deep earthquake plane occurs at approximately 110 kilometers directly beneath the volcanic front, which indicates that the formation of the volcanoes is closely associated with the subduction of the Pacific plate.

In western Japan, there is a volcanic front that runs from the San-in region through Kyushu and then spreads toward the Tokara Islands. This volcanic front is formed as result of subduction of the Philippine Sea plate.

Volcanoes which erupted in the past 10,000 years are defined as active volcanoes, and they have the potential to erupt again in the future. There are 108 of such active volcanoes are recognized by the Japan Meteorological Agency (Figure 1). Regardless of their scenic beauty and neighboring hot springs that attract sightseers and climbers, however, most of the recognized volcanoes, once reactivated, may cause serious destruction to themselves and surrounding areas.

AIST has been making geological maps of past eruptions of active volcanoes since the time of our antecedent, the Geological Survey of Japan, and has been providing them as geological maps of volcanoes. Questions such as when, where and how a volcano erupted and affected can be determined based on our intensive study of past distribution of erupted products, eruption time and characteristics using field surveys and laboratory experiments.

Each volcano has its own varying characteristics, patterns, frequencies, and scales of eruption. The geological map of a volcano can be referred to as a resumé of the volcano since the time it was formed by clarifying such differences mentioned above. The geological map of a volcano will help with prediction of shift in the activity when an eruption is imminent or actually begins. The data on patterns and scales of past eruption are used as basic material to establish hazard map (a chart of expected damage due to an eruption) by local administration.

Quaternary volcanoes are referred to those active within the last 1.8 (or 1.7) million years, naturally, including the active volcanoes. In this particular time span, the general distribution trend and range of volcanoes are similar to those of the active volcanoes shown in Figure 1. There are more than 300 Quaternary volcanoes recognized in Japan. For example, Gassan in the Tohoku region, Nantaisan in Nikko, and Daisen in the San-in region are famous volcanic mountain though not active. Should a volcano that erupted within the last 10,000 years reactivate we will label it as an active volcano.

Within AIST’s research database (RIO-DB), data on Quaternary volcanoes are open to the public. The data cover all the volcanoes that were active during the Quaternary. Data include volcano type (stratovolcano or lava dome), rock type (basalt, andesite, etc.), activity period, names of topographic maps showing locations of volcanoes (longitude and latitude) and related literature. The data also contain eruption records and pictures of the active volcano. Geological maps issued by AIST are to be added to the database in addition to a plenty of pictures for each volcano. At the present, the database is available in Japanese, but in the near future, English version will be published. In general, it is planned to be developed to a more detailed and socially useful database.