Mt. Asama is one of the active volcanoes in. Japan. Pyroclastic flow caused by the eruption of a volcano is a mixture consisting of pyroclastic materials and high-temperature gases. Its maximum speed down the surface of a volcano is estimated at about 100m per second. In 1995, the municipalities (two cities, three towns, and one village) surrounding Mt. Asama constructed a volcanic hazard map. The pyroclastic flow shown in the hazard map was predicted using the Bingham flow model on the basis of geological maps and historical documents on volcanic activities. This hazard map predicted two pyroclastic flows on the southern slope of Mt. Asama during the first five minutes, and 10, 15, and 30 minutes after eruption.
This paper attempts to construct a prevention plan support system using GIS to predict the risk caused by the pyroclastic flows shown on the volcanic hazard map. The support system consists of three components: a map database, map representation, and spatial analysis. Layers for population, road networks, railroads, motorways, and public facilities were, each overlaid with the layer of pyroclastic flows.
Using the INTERSECT command in ARC/INFO, it was possible to estimate the volume of population, road networks, railways, motorways, or public facilities endangered by the pyroclastic flows.
The area covered by the pyroclastic flows is predicted to be 2, 529 hectares, and the number of people affected by the pyroclastic flows will total about 3, 500. The total length of roads blocked by the pyroclastic flows is 34.5km, including about 1.9km of National Road Route 18. Railroads and highways will be affected within 10 to 15 minutes.
The prevention plan support system was also applied to define emergency planning zones and formulate an evacuation and rescue plan. The area covered by the pyroclastic flows and a 500 m buffer zone around it are designated as emergency planning zones of risk 1 and 2, respectively. It was found that 26 existing refuges located in the zones of risk 1 and 2 cannot be used in a volcanic disaster. Network analysis was applied to formulate an evacuation plan on the road network for residents in the zone of risk 1. As a result, it became clear that residents affected within 10 minutes will not be able to escape on foot. Refugees escaping from the zone of risk 1 will be allocated to the nearest safe refuges in terms of road network distance, considering their capacities. The average distance from residential areas to the refuges was about 2.7 km. As a result of searching for the shortest path as a bypath for the disconnected sections of the National Road, it is predicted that rescue activities will be disordered because the bypath is 1.6 times as long as the normal route on the National Road and it is also too narrow.

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Glaciation in the Hidaka Range, Hokkaido, the northernmost island of Japan, has been a key issue in Quaternary research in Japan. However, precise descriptions of glacial deposits and their stratigraphic and chronological structures, particularly based on tephrochronology, are lacking. In the present paper, the chronology of Late Quaternary glaciation in the uppermost Tottabetsu Valley, Hidaka Range, was examined based on the distribution and stratigraphy of glacial landforms, glacigenic sediments, and marker tephras. Three marker tephras, the Toya tephra which erupted at 100-106 ka, Kuttara-6 tephra (Kt-6: 86 ka), and Rakko pumice 3 (RP 3 : 75 ka), are found in the nonglacial deposits overlain by a typical subglacial deformation till. Deformation features indicating subglacial tills, such as shears and fracture zones, were observed in several exposures. The valley glacier that generated these deformation tills and related fluvioglacial sediments probably formed the lateral moraine overlain by Shikotsu-1 tephra (Spfa-1: 40-42 ka). On the other hand, Eniwa-a tephra (En-a) which erupted at 17-18 ka is found in almost the whole horizon of fluvioglacial sediments at some locations close to cirque floors. Our examination revealed the age and extent of the maximum glacial advance during the Poroshiri and Tottabetsu stadials of the Last Glacial stage. The Poroshiri stadial glacier grew into a valley glacier reaching its maximum at 850 m a.s.l. around the eruption age of Spfa-1 (40-42 ka). The Tottabetsu stadial glacier probably including the so-called Last Glacial Maximum reached its maximum at 1250 m a. s.1, before the eruption of En-a (17-18 ka). En-a is considered to have covered the glacier surface, causing a sudden melt-out and sedimentation of fluvioglacial deposits. After the maximum glacial advance of the Tottabetsu stadial there were at least four short stages of stagnation or readvance of the glacier represented by a series of terminal-lateral moraines.
Older glaciation occurred before the eruption of the Toya tephra (100-106ka), which is represented by the stratigraphy of older glacial deposits and a buried glacial trough. This glaciation, the Esaoman glaciation, is regarded as the penultimate glaciation (oxygen isotopic stage 6), or possibly older glaciation. The glacier during this stage formed a clear U-shaped valley and extended lower than that during the Poroshiri stadial of the Last Glacial stage.

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