There are 108 active volcanoes in Japan, which repeat eruptions. Even large-scale volcanic activities which require the evacuation of local residents occur every five years on average. Modern volcanic observation network has allowed us to almost certainly catch the signs of a large-scale eruption beforehand. However, currently it is difficult to predict the style and the duration of an eruption as well as the shift of volcanic activities beforehand.

Accurately grasping the state of volcanic activities and having a clear picture of the shift in activities is necessary in order to reduce the damage of an eruption. Therefore, the Coordinating Committee for Prediction of Volcanic Eruptions will collect detailed observational data and analyze volcanic activities at the brink of an eruption. AIST is conducting surveys on eruption products, volcanic gases and of ground deformation in cooperation with the Japan Meteorological Agency, Universities, and related research institutes. Cooperation from many researchers in various fields is necessary in order to conduct urgent and concentrated surveys and research when an eruption occurs. Thus, emergency observation task force team may be created temporarily, for example AIST set up the Emergency Countermeasure Headquarters, in which our vice chairman was assigned as the chief, and nearly 40 staff cooperated when the eruption occurred on Miyake-jima.

Volcanic activities on Miyake-jima which began in June, 2000 were large-scale ones said to have happened for the first time in 3000 years. All residents were forced to evacuate from the island due to possible eruptions followed by the release of a large amount of volcanic gases.

When an eruption occurs, the most important thing is to determine the characteristics of the eruption based on a local survey and predict subsequent volcanic activities. On Miyake-jima, a collapsed crater of 1.6 kilometers in diameter was formed on the summit of the volcano in July and August with repeated eruptions. During the eruptions, AIST researchers conducted surveys in the island covered with volcanic ash and studied the distribution and the amount as well as the form and the composition of eruption products (volcanic ash and volcanic bombs) to determine the characteristics of the magma which caused the eruptions.

On Miyake-jima, large amounts of volcanic gases were continuously released after the formation of the collaped crater, a rare phenomenon globally. Residents of Miyake-jima are still in evacuation because these poisonous volcanic gases continue reach to residential areas.

AIST is continuously monitoring the emission and the composition of volcanic gases as well as other activities in cooperation with the Japan Metrological Agency and Universities, since precise understanding of volcanic activities is the key to judge the risk of an eruption and volcanic gases. An urgent and detailed survey of an eruption is not only necessary to directly reduce damage, but also important as the basic research in volcanology. An eruption is a precious opportunity for research.

Mankind has not experienced many eruptions since the development of modern observation methods. Therefore, volcanic researchers who have experienced actual eruptions are like doctors treating patients with rare diseases and are invaluable within their fields. Researchers at AIST are conducting front-line surveys and research on eruptions, aiming to reduce damage and hazards by developing a better understanding of volcanic processes.

The use of satellites enables us to monitor volcanic activities safely, extensively, periodically, and consistently. Satellites are especially effective at volcanoes where observations from the ground are difficult. For example, Mt. Chachadake on Kunashiri Island, one of the most active volcanoes, has a severe natural environment in addition to some political issues, making it the most difficult volcano for ground observation.

Figure 1 is an image of Mt. Chachadake observed by the ASTER sensor developed by the Ministry of Economy, Trade and Industry. We can observe that vegetation near the south and north caters is not recovered yet which was dameged by 1973 Eruption.

Figure 2 is a topographical map created by using the stereo-image function of the ASTER sensor. The topographical map of this region had not been updated since it was issued by the Geographical Survey Institute in 1922. The new topographical map shows the detailed topography of the south crater and the north crater.

Figure 3 shows the distribution of surface temperatures on Mt. Chachadake observed at night; the brighter parts indicate high temperature, and the darker parts indicate low temperature. Even though the surface temperature lowers as the height above sea level increases, brighter points can be found on the summit of Mt. Chachadake. This indicates higher surface temperatures on the summit than in the surrounding areas due to volcanic activities. Meanwhile, no heat abnormalities are found in the south or north crater. The temperature of the sea on the north side of the island is low because of drift ice alongside the coast, while the temperature of the sea on the south-side of the island is higher than the land temperature.