In order to examine the geomorphological features of Mt. Fuji, 50m DEM data of XY format were converted to a cylindrical coordinate system, in 15km radius from the center of the summit part. The results are summarized as follows; (1) Towards the northwest and the southeast directions from the summit of Mt. Fuji, many pyroclastic cones provide a topographical feature like “bulge”. And slight bulge in the northeast direction but no pyroclastic cone. (2) Mt Fuji is conical in shape, becoming to be gentle in accordance with the distance from the peak. The form was supposed to be overlapped results from different angle of repose for various cones and deposits. (3) Mt. Fuji is composed of various kind of deposits from the summit to the lower slope, such as welded airfall deposit, pyroclastics, lava flow, pyroclastic flow deposit and debris flow deposit. (4) The slush fan deposits by slush avalanches, with a gradient between the lava flows and tephra falls. The slush avalanche deposits take role in the formation of beautiful conical shape of the Mt. Fuji.

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Slush avalanches often occur on the slopes of Mt. Fuji, 3776 m high stratovolcano in Central Japan, mainly in spring season and also in early winter. Recent researches clarified that Yukishiro, high waves of debris flow documented in archives of Japanese medieval to Edo-era, were induced by slush avalanches. Field permeability tests on frozen slope were conducted. Interparticle void in frozen soils was gradually blocked up by ice crystals and deducted soil permeability. It is a reason how rain and/or melt water retains in snow on the permeable scoria slopes and turn instable snow layers around Mt. Fuji. New observation system and cryo-meteorological data accumulation are necessary for more detailed studies.

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Slush avalanche event in Mount Fuji has most frequently occurred in the southeastern slope as well as Kengamine Osawa valley (Osawa-kuzure). Asymmetric vegetation and landscape between the southeast slope and the other side are caused by not only direct impact from the 1707 Hoei eruption but also succeeding such slash events. During from late 2006 to the 2009, seven slush events were ascertained. These event started from the approximately same dried-up shallow valleys as scoria mixed slush avalanche and subsequent mud flow. Fresh sedimentary and eroded topography were formed by these events, at the middle and lower part of the shallow valleys. Aerial photographs show that similar valley heads have existed at the same location at least past 60 years. Thus, volume of aggradation and erosion within these valleys are equal in quantity owing to repeated slush events. Passing the well-developed low pressure system in Japan sea were observed in every slush event in common with previous studies. Difference of sea level pressure between the northwestern and southeastern side of middle part of the Honshu island can reveal such atmospheric pressure distribution. Furthermore, air temperatures approximately -5 2C at the summit and +13 2C at Gotemba, and precipitation approximately 10 mm/hour at Inno and Akatsuka can be considered as the meteorological threshold for occurrence of slush avalanche in the southeastern slope. Hence, these obvious tendencies and thresholds of the meteorological elements may allow the establishment of a objective criteria for disaster prediction for slush avalanche. For the further verification of occurrence condition, it is necessary to observe the extent of the minor slush events and obtain the meteorological data in the all direction of flank of Mount Fuji.

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Slush avalanche is one of the natural disasters of Mt. Fuji, causing severe damages in the mountain area every several years. A seismic network has been developed since 1990s for the eruption prediction research of Mt. Fuji, and the ability of seismic signal detection has been greatly improved especially for recent five years. The seismic network has detected several slush avalanches, providing useful information about the time and duration of them for us. We show here that the seismic network is potentially a useful tool for monitoring slush avalanches.

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Slush avalanche occurs on Mt. Fuji is one of the phenomena that turn out the flood and the debris flow disaster. Objective of this examination attempt the improvement safety of the local areas by forecasting the occurrence of slush avalanche and offering the disaster prevention information. This report concluded that occurrence of slush avalanche relates deeply to weather conditions, and there is a feature in a multistory weather situation. Moreover, mechanisms of slush avalanche were seized by the field observation and the image analysis. The image of slush avalanche occurred on March 25th 2007 was recorded by the CCTV camera. From these results, we investigated forecast technique and the prospect of deciding on the judgment index from weather conditions.

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When a volcano erupts in the snow season, mudflow by snow melting occasionally occurs, causing destructive disaster. On May 24, 1926, after an explosive eruption of Mt.Tokachi, hot debris avalanche melted the remaining snow, and caused big mudflows that attacked a hot-spring hotel and a village of Kamifurano. The village was buried under mudflow sediment and completely destroyed. 144 people were killed in total. Recently, on November 13, 1985, similar disaster was experienced after an eruption of Nevado del Ruiz Volcano, Columbia. As a pyroclastic flow from the summit crater covered the surface of glacier, rapid melting of ice triggered disastrous mudflows. The mudflow travelled about 50km and devastated the city of Armero, where 21000 of 29000 inhabitants were killed. About one month before this eruption, a detailed hazard map of Nevado del Ruiz Volcano had been circulated by INGEOMINAS ,the Geological Survey of Columbia, to local autonomies. This map was well prepared and the mudflows flowed down along the predicted courses. But each autonomy could not put the map to practical use for real disaster prevention. As soon as hearing the news about the disaster at Nevado del Ruiz, Kamifurano town prepared a new hazard map for emergency evacuation on the assumption that mudflow attacks the town after an eruption of Mt. Tokachi. Actually, when the volcano erupted on December 25, 1988, evacuation of inhabitants was directed on the basis of this hazard map. In Japan, mudflow disaster by snow melting with volcanic eruption has not been caused more than 80 years after the disaster of Mt.Tokachi in 1926. But, if in future, volcanoes including Mt.Fuji erupt on a large scale at the snow season, surrounding areas may face the danger of destructive mudflow. Accordingly, autonomies around active volcanoes have to prepare the disaster prevention planning against mudflows by snow melting with eruption.

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The relationship between the historical glacier fluctuation and the outburst flood of glacier-dammed lakes was analyzed at Hunza Valley in the Karakoram Mountains, Pakistan. As a result, glaciers such as Batura, Pasu, Ghulkin, Hasanabad, Minapin, Ghulmet and Biafo have repeated glacier progressions of about 10Ò20 years after long retreat periods (1860-1907, 1913-1960 and 1980- ) since AD 1860. In addition, it is thought from the growing environment of Jeniperus distributing in the Valley that temperate periods (1865-1895, 1915 -1950 and 1975-1995) appeared in the 20-25 year cycle repeatedly. A relationship between the glacier fluctuation and such climatic condition shows that the glaciers accompanied with a response time of 10-12 years have sensitively responded to climatic changes in the Valley. While, six periods of the outburst flood in Hunza and Shimshal valleys, which appeared in the about 20 year cycle correspond to the retreat periods of the glaciers. It shows that the glacier retreat depending on climatic warming is the trigger of the outburst flood of glacier-dammed lakes, which is preceding the increasing of the melting ice and the expansion of lake area.

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Mount Fuji, the highest peak in Japan, has repeated active eruptions, producing a steep conical volcano together with strong denudation. Its steep slopes, alpine environments and steep lava sheet structures are subject to rapid development of dissected valleys. Osawa valley, the largest valley of the volcano, was started to form by initial rock-slide avalanche possibly triggered with large earthquake occurred 700-900 years ago, since then towering cliffs have suffered a sharp setback with mass movements, mainly by frost heaving and melting. Before the Osawa rockslide avalanche Mount Fuji had changed its landform significantly suffered from extraordinary large scale collapses and avalanches several times since the last glacial period. The recent one is called Gotemba debris avalanche and associated mudflow event dated about 2900 years ago. The other called Fuji-Sagamigawa event about 21,000 years ago was possibly the largest of collapses occurred during the last glacial period. The source caldera-like walls are not clear at present because they were followed by very active cone building activities. Some archeological evidences suggest that both events gave great impacts on prehistoric people living around the foot of Mount Fuji and adjacent river valleys. Fluvial fill and cut landforms along several rivers originating from Mount Fuji show significant environmental changes. Triggers of both events are not so clear but possibly by large earthquakes or phreatic eruptions. Ice-melting caused by some eruptions would have been responsible for forming Fuji-Sagamigawa mudflows in the last glacial maximum period.

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Permafrost degradation is a globally focused issue under the recent climatic warming. In this context, rapid degradation of permafrost on Mt. Fuji was reported by the mass media in Japan. However, the present scientific knowledge of the permafrost is not enough to evaluate the extent of the degradation because the distribution and thermal conditions of the permafrost itself have remained mostly unknown. Thus, in 2008, young researchers studying permafrost worldwide launched a project to monitor permafrost on Mt. Fuji using geophysical techniques. Two boreholes about 3 m deep were dug on the summit area, and ground temperatures and meteorological parameters, such as air temperature and precipitation, have been monitored since the end of August. Ground-penetrating radar was applied to sound the distribution of permafrost on the summit area and south-facing slope. The preliminary data on the ground temperature are significantly high, despite the cold air temperature at the summit. Permafrost absence was confirmed in the one of the boreholes. The velocity of electromagnetic (i.e. radar) wave possibly suggests permafrost absence at shallow depth on the most part of the　south-facing slope. These results indicate that a high ground thermal condition by volcanic　activity should be considered in permafrost research on Mt. Fuji.

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The Shirouma-Daisekkei Valley Route to Mount Shirouma-dake (2932 m ASL) is one of the most popular mountain trails in Japanese Alps. Every summer, more than 1000 climbers pass through this route a day. Along this route, however, serious accidents involving climbers have been caused by a wide variety of geomorphic changes such as rockfall, slope failure, supranival block slide and debris flow during the period from summer to fall. For establishing safe mountaineering along this route, geomorphic changes and other physiographic conditions (e.g., microclimate) should be evaluated quantitatively. Safety supports and general education for the climbers in partnership with the public administration, tourist agents, mass media and researchers are also required.

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Mt. Fuji is a symbol of Japan and is an object of faith of Japanese people, more from ancient times. She was registered into the provisional registration list of World Cultural Heritages in 2007. However, she is in the situation where being formally registered as world heritage takes time for a while. More than 300,000 tourists are climbing a mountain to the Mt. Fuji top in the mountain-climbing season of the summer of 2008. Therefore, the natural environment of Mt. Fuji is getting worse. She has been disgraced with a mountaineer's excrement and garbage. It is a situation which cannot be recovered by the self-purification power which Mt. Fuji has her own power. Moreover, her surface is full of cracks by the mountain trail and the way of the bulldozer for carry a heavy load up the summit. It is important to hand down Mt. Fuji to future generations as a symbol of Japan which prides itself in the world. Therefore, the present, Japanese people are asked for impulsion of the conservation of nature, and reexamination of sightseeing mountain climbing.

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The symposium was concluded by general discussion. Some problems and opinions of the hazard map, tourism facility, study of complex slush event and mud flow in the glacier age were remarked from the speakers. Furthermore, as the common perceptions, the audiences, speakers and introductory speaker emphasized that the most important issues of safety management from the act of Mt. Fuji are not only collecting data and further installation of observation equipment, but also cooperation among research organizations, data sharing and information providing for the public and visitors. Providing the information for them, regarding yearly slope disaster, such as small slush avalanche and rock fall phenomena in Mt. Fuji will remind people about actual potential of disaster in an apparently quiet Mt. Fuji.

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