Many Japanese geographers know the great contribution of the late Carl Troll to mountain geoecology. However, it is not necessarily well known for Japanese geographers that the discipline has been developed by the U.S. geographers since the 1960s. This paper briefly examines roles of the Institute of Arctic and Alpine Research (INSTAAR) and the International Mountain Society (IMS) in the development of the discipline; and then, reviews the major studies conducted in the Colorado Front Range, Ecuadorian Andes and Nepal Himalaya. The first stage of the development of mountain geoecology in the U.S. is characterized by basic studies which have been conducted mainly by the INSTAAR of the University of Colorado, Boulder. Mountain-geoecological studies have been regarded as one of the major activities for the INSTAAR since the institute's establishment in 1951. Numerous studies were carried out on Niwot Ridge, Colorado Front Range, at the foot of which the Mountain Research Station of the university is located. Most studies have emphasized physical aspects. The journal, Arctic and Alpine Research, which has been published by the INSTAAR, has carried many of such papers. In the 1970 s the movement to establish a new academic society rose, and in 1980 the International Mountain Society (IMS) began to function in the University of Colorado, succeeded by the University of California, Davis, in 1990. The IMS, founded by Jack D. Ives, has been publishing the quarterly journal, Mountain Research and Development, since 1981, with the collaboration of the United Nations University, Tokyo. Among their main research field of their projects including Northern Thailand, Papua New Guinea, and Ethiopia, the main results from the Ecuadorian Andes and Nepal Himalaya were reviewed. These studies characterize the second, or today's, stage of mountain geoecology. That is, one of the major interests of mountain geoecological studies today centers upon human and physical interrelationships. Recently, the Japanese mountain areas have been used extremely intensively, so that mountain geoecology is hoped to contribute to solve the problems of the mountain environments in Japan.
An exploratory trench was excavated across the Midori fault scarp associated with the Nobiearthquake (M 8.0) of 1891, which was the largest earthquake recorded on inland Japan. The trench has been preserved for exhibition by covering it with a building and grouting it to prevent leaking of ground water. This preservation and exhibition of an exploratory trench across a seismic fault is the first attempted in the world. The Midori Fault exposed on the trench walls has a strike of N 35°W and is almost vertical. The upthrown side of the fault consists of Mesozoic sedimentary rocks and alluvial gravel. The downthrown side consists, in ascending order, of wide fault gouge derived from Mesozoic rocks, alluvial gravel, paleo-soil, gravel due to collapse from the upthrown side and artificial fill. Clasts within alluvial gravel along the fault are rotated by the fault movement. The pre-1891 sediments have been displaced vertically by 5.5 to 6 meters and left-laterally by about 3 meters, indicating the Nobi earthquake of 1891 was the only seismic event on this fault over at least 1, 000 years that caused displacement.
The stratigraphy, geologic structure and ages of the Mesozoic strata exposed in the eastern part of the Kanto Mountains, central Japan, are discussed based on recent fossil findings. The Jurassic formations trending WNW-ESE direction, are subdivided into the following six formations from north to south: the Kuroyama, Takahata, Kabasaka, Hanagiri, Nakato and Nitayama Formations. The Middle Jurassic Kuroyama Formation is composed of chaotic rocks consisting of exotic blocks of Permian to Early Jurassic chert, Carboniferous to Permian limestone and volcaniclastic rocks in a shaly matrix. The Takahata Formation consistsof Middle Jurassic shale and volcaniclastic rocks with Permian limestone blocks. The Kabasaka Formation is characterized by a chert-clastic sequence, which is made up of Triassic to Early Jurassic chert and overlying Middle Jurassic shale. The Early Jurassic Hanagiri Formation is composed of chaotic rocks consisting of exotic blocks of Permian to Early Jurassic chert, Permian limestone and volcaniclastic rocks in a clastic matrix. The late Early Jurassic Nakato Formation is composed mainly of chaotic rocks consisting of exotic blocks of Permian to Early Jurassic chert in a shaly matrix. The Nitayama Formation is characterized by chaotic rocks comprising of Permian to Early Jurassic chert and Permian limestone in a Middle Jurassic shaly matrix. The first three formations are in contact with vertical or steeply southward-dipping faults. On the contrary, the latter three are in contact with northward-dipping reverse faults. The Koma Orbitolina Formation, which consists mainly of Early Cretaceous calcareous shale and sandstone unconformably overlies the Takahata Formation in the most eastern part of the studied area. Based on stratigraphical and structural features and radiolarian dating, the Kuroyama, Takahata and Kabasaka Formations are correlative with the Northern Chichibu Belt (northern portion of the three folds Chichibu Belt) in the Outer Zone of Southwest Japan. The Kabasaka Formation is regarded as an accretionary wedge formed by offscrape-accretion mainly during Middle Jurassic time. The Hanagiri, Nakato and Nitayama Formations correspond to the Middle Chichibu Belt and are presumed to be products of the convergent complex of an oceanic plate during Early to Middle Jurassic times.
The author investigated periglacial smooth slopes in and around Mt. Yakushidake (2, 926m), the Northern Japan Alps, to discuss geomorphic altitudinal zonation since the later Last Glacial stage. Present geomorphic altitudinal zonation can be regarded as follows: Zone I (none): block field zone Zone II (above 2, 700m): deep reaching and free solifluction zone (periglacial rubble slope zone) Zone III (2, 400-2, 700m): shallow and partly bound solifluction zone Slope materials of present periglacial smooth slopes higher than 2, 700m above sea level and adjacent fossil ones have various characteristics, that is, surface openwork rubble layers, structures of particle sorting and/or multi-layers of debris, as well as platy or bladed layers, silt cap and sorted free grain accumulation under boulders. These are assumed to be due to freeze-thaw processes or advances of solifluction lobes. Therefore they can be regarded as good indicators of fossil periglacial slope deposits. In view of the distribution of fossil periglacial smooth slopes and characteristics of slope materials, geomorphic altitudinal zonation during the later Last Glacial stage is assumed to have been as follows: Zone I (block field zone): above 2, 500m Zone II (deep reaching and free solifluction zone; periglacial rubble slope zone): 2, 100 or 2, 200-2, 500m Zone III (shallow and partly bound solifluction zone): 1, 700-2, 100 or 2, 200m Though periglacial smooth slopes were formed through the Zone I-II and III, in the Zone III freeze-thaw processes were not so dominant but slope wash and/or alpine debris flows played major roles in their development. Scars of collapses, as well as periglacial smooth slopes, were formed predominantly in the Zone ifi during the Glacial stage. Periglacial rubble slopes were wider during the period after 4, 500 BP than those in the previous time and in the present. During this period the lower boundary of the periglacial rubble slope zone (Zone II) is assumed to have been placed at about 2, 600m. Taking a broad viewpoint, it coincides with the global cold period after the Hypsithermal (the Neoglaciation).