山田 周二

Soil temperature, surface heave and downslope movements were monitored continuously for one year (1998-99) within a solifluction lobe developed on seasonally frozen ground in the Daisetsu Mountains, northern Japan. Observations were also made of soil moisture and ice segregation. Seasonal freeze-thaw cycles produced both frost creep and gelifluction. In layers shallower than 60cm, ice segregation during the freezing season induced seasonal frost heave, and ice melt at the same depths during the thaw season promoted gelifluction as well as seasonal frost creep. At greater depths, gelifluction did not occur even when the thaw plane reached the ice-rich layers. The results at the study site demonstrate that segregated ice plays an important role in gelifluction, but only at shallower depths. Copyright (C) 2010 John Wiley & Sons, Ltd.

社会科の地理的分野において,身近な地域学習は地理的な見方や考え方の基礎を培うための重要な単元と位置づけられている。この単元において学習効果の望める教材を開発するため,本研究は大阪教育大学附属平野中学校の選択授業を通じて,GISを用いたカリキュラム開発およびその実践を行った。その結果,交通量と交通事故の分布には明瞭な関係が読み取れ,生徒も容易に分布の傾向を読み取ることができることが明らかになった。Educational practice of a regional study on the distribution of traffic accidents around the school was carried out using geographical information systems in Hirano Junior High School attached to Osaka Kyoiku University. The practice indicated that a lot of traffic accidents happened on a main street where traffic is very busy. Students could easily read the relationship between traffic density and traffic accidents. Thus, fieldwork for traffic density and traffic accidents is suitable for regional study.

地理教育における身近な地域の学習を効果的に進めていくために,大阪教育大学附属平野中学校の選択授業を通して,GISを用いたカリキュラム開発およびその実践を行った。その結果,身近な地域の学習を進めていく上で,どのような地理的事象に注目し課題設定するのかが最も重要なことであり,特に人通りに注目し,野外調査や結果の分析を行い,飲料自動販売機の分布と比較する学習が,高い効果の望める活動であるということが明らかになった。Educational practice of a regional study on the distribution of vending machines was carried out using geographic information systems in Hirano Junior High School attached to Osaka Kyoiku University. The practice indicated that vending machines are clearly distributed in and around commercial districts. Also, traffic of pedestrian converged in and around commercial districts. Thus, field work for vending machines and pedestrian is suitable for regional study.

Yamada and Kurashigeが1996年に発表した改良型ストレインプローブ法は,クリープ性の土壌変形を検出するには極めて有効な手法である.しかしこの方法では,土壌のせん断変形を検出することができなかった.土壌がせん断変形する際のせん断層厚は数cmである.しかし,従来法は大型ゲージ4枚で1区間10cmの平均的曲率を検出するように設計されているため,上述のような局所変形を検出できない.これを克服するには,1区間の長さをできるだけ小さくすればよい.しかし従来法では,たとえゲージ4極法を2極法に改善したとしても,ゲージから伸びるコードの数が多くなるほどプローブ本体の弾性変形を阻害するようになる.このため,区間数をあまり多くすることはできない.この問題を解決するため,プローブの心材として使用するバネ鋼表面にフレキシブルプリント配線(FPC)を用いることにした.その上でゲージ2極法を使用した全長48cm,区間長4cm,区間数12のプローブを試作した.このプローブに対し変位5mmのせん断変形をせん断層厚6cm,4cm,2cmの3ケースについて与えた.その結果,せん断層厚6cmと4cmの場合には変位を誤差1mm程度で検出できたが,せん断層厚2cmの場合は変位を検出できる率が33%程度だった.すなわち,1区間の長さがせん断層厚以下のストレインプローブを作成すれば,そのせん断変形を検出できることを確認できた.

学校教育において地理情報システム(GIS)を効果的に利用するために,モバイルGISを援用した授業実践を大阪教育大学附属平野中学校で行った。GPS受信機を内蔵した携帯情報端末(PDA)を用いて,野外調査を行ったところ,生徒は容易に機器を操作することができ,また,紙地図を用いて野外調査を行いデスクトップPCでデータ入力を行うよりも非常に効率よく多くのデータを入力することができた。Educational Practice of regional study was carried out using mobile GIS in Hirano Junior High School attached to Osaka Kyoiku University. Personal digital assistant (PDA) with GPS receiver and mobile GIS software was used for field work. Students of the junior high school could easily use the system. Further, the efficiency of the data input using the system was grater than that using Desktop PC.

Field measurements of the morphometric characteristics of 86 solifluction lobes in the Daisetsu Mountains were made. Solifluction lobes were classified into three types: type A lobes have a tongue-like form without any distinctive micro-topography: type B lobes are also tongue-like, but have small collapses on the lobe front: type C lobes are characterized by a depression in the rear part of the lobe. The ratio of lobe width w to lobe length l, w/l, is constant for each type, showing that the longer the lobe, the greater its width. This relationship suggests that the frontal advance of a solifluction lobe is accompanied by lateral development. The lateral development seems to be controlled by a balance between the frontal advance and the sediment supply from the back slope: lateral development occurs when the sediment supply from the back slope exceeds the frontal advance.

This study classified Japanese mountains based on mountain ordering using 1 : 500000 topographic maps, and examined the relationships of relief, relative relief and perimeter fractal dimension for the classified mountains. Mountain order was defined in terms of closed contour lines on the topographic map. A set of closed, concentric contour lines defines a first-order mountain. Higher-order mountains can be defined as a set of closed contour lines that contain lower-order mountains and that have only one closed contour line for each elevation. Relief, relative relief and fractal dimension were measured for ordered mountains using personal computer, and were defined as follows : relief E = H/A^1/2, where H and A are the height and area of each ordered mountain, respectively; relative relief R= ∑ h_i/H, where h_i is the height of the enclosed, lower-order mountains, and represents the degree of vertical roughness of the ordered mountain; fractal dimension was measured for perimeter contour line by the pixel dilation method, and represents the degree of horizontal roughness of the ordered mountain. Japanese mountains were classified into 74 third order mountains and 11 fourth order mountains. The area of a third order mountain varies from 50 to 4712 km², and that of a fourth order mountain is 2498 to 15563 km². A significant relationship was found among relief E, relative relief R, and fractal dimension D for the ordered mountains (r=0.91, n=85), and can be defined by the expression : <BR>LogE=-aD-bLogR-c<BR>This relationship shows that Japanese mountains have the following morphological characteristics : a high relief mountain has low vertical and horizontal roughness, and a low relief mountain has high vertical and horizontal roughness. These characteristics suggest that slope angle of Japanese mountains converges within a certain range.

人工的に改変された山地・丘陵地の地形の自然さを定量的に評価するために,大都市(東京,大阪,名古屋)近郊の宅地およびゴルフ場として改変された山地・丘陵地を対象として地形計測を行った.まず,地形改変前および後に作成された2万5千分の1地形図を用いて,起伏E(比高と面積の平方根との比),相対起伏R (垂直方向の凹凸の程度を表す指標),輪郭の等高線のフラクタル次元D (水平方向の凹凸の程度を表す指標)を計測した.地形改変前の,三つの地形量の間には有意な相関があり (r=0.79,n=69, p<0.0001), LogE=-0.31D-0.58LogR-0.56で回帰平面が表された.この回帰式および実際のRおよびDの値から, LogEの計算値を求め,これと実際のLogEとの差を地形自然度と定義した.改変前の山地の地形自然度はゼロに近い値をとり,平均値はゼロ,標準偏差が0.15になった.一方,改変後の山地では,マイナスの値が多くなり,宅地およびゴルフ場では,平均値がそれぞれ-0.20および-0.05になった.このような結果は,地形自然度という尺度が人工的に改変された地形を有効に評価し得ることを示す.

Creep and temperature were monitored continuously from August 1996 to September 1997 in a solifluction lobe occurring over alpine, seasonally frozen substrate in the Daisetsu Mountains, northern Japan. The seasonal freeze-thaw cycle (&gt;100 cm in depth) caused relatively deep (95 cm in depth) frost creep (approximately 4 cm per year at the surface), whereas diurnal freeze-thaw cycles did not yield any measurable soil displacement. Diurnal freeze-thaw cycles took place frequently in autumn and spring (29 events per year), although the freezing was very shallow (&lt;10 cm). Because the soil at the measurement site has a surficial openwork bed that is non-frost-susceptible, the shallowness of the diurnal freeze-thaw cycles precluded surface frost creep. Since the soil is at least 100 cm thick, soil water stored induces frost heave and resultant creep at depth. Copyright (C) 2000 John Wiley & Sons, Ltd.

A new method for classifying mountain morphology, 'mountain ordering,' is proposed, and quantitative expressions for various morphological parameters of two ordered mountains in northern Japan were obtained using this method. Mountain order was defined in terms of the closed contour lines on a topographic map. A set of closed, concentric contour lines defines a first-order mountain. Higher-order mountains can be defined as a set of closed contour lines that contain lower-order mountains and that have only one closed contour line for each elevation; they are identified as m + 1th-order mountains, where m represents the order of the enclosed, lower-order mountains. The geomorphometry for a mountain ordered according to this definition permits the identification of systematic relationships between various morphological parameters. The relationships between mountain order and these morphological parameters follow a form similar to that of Horton's laws, and permit the calculation of the ratios of number, area and height; these parameters are sufficient to express the magnitude of a mountain's dissection. The sits-frequency distribution for area and height shows self-similarity for ordered mountains, and determines their fractal dimensions. Furthermore, the relationship between area and height, which has the form of a power function, describes the relief structure of ordered mountains. Copyright (C) 1999 John Wiley & Sons, Ltd.

Field measurements of soil creep and slope stability were conducted on a nose, side-slope and hollow in a zero order basin near Sapporo, Hokkaido, northern Japan, and the preferential location of soil creep and slope failure was determined. Soil creep was continuously measured by the strain probe method at three sites from 1994 to 1995, and was compared with soil moisture conditions and ground temperature. In the summer, active soil creep occurred only when rainfall led to large soil moisture changes and a near-saturated condition, which was most likely induced by shrink-swell activity of soil. In the winter, soil creep was caused by seasonal frost, although the mass transport was limited because of the insulation provided by snow covet. These results indicate that the soil moisture change and soil moisture content during a rainfall event in the summer are the major factors controlling soil creep in this basin. Soil moisture conditions were further measured by a tensiometer at 16 sites in the rainy season in 1994. On the nose and side-slope, active soil-moisture changes took place during rainfall-events. The hollow tended to maintain higher soil-moisture conditions than the nose and side-slope, because subsurface flow was concentrated in the hollow. Thus the soil-moisture variation that encourages soil creep rarely occurred in the hollow. From these results, sediment transport rates caused by creep were estimated to be 207.0, 159.5 and 9.0 x 10(-3) m(3)/yr on the nose, side-slope and hollow, respectively, and the resultant mass balances were calculated at - 207.0, +25.1 and + 172.9 x 10(-3) m(3)/yr, respectively. These results clearly show infilling in the hollow and denudation on the nose. Slope stability was analyzed by the infinite slope model. The potential of slope failure was evaluated from the relationship between critical water depth H-cr and soil thickness D. The analysis revealed that an increase in D causes a marked decrease in H-cr on the side-slope, indicating the high potential of slope failure on the slope. In contrast, both on the nose and in the hollow, the decrease in H-cr for the same increase in D was lower than that on the side-slope. However, slope failure on the side-slope and soil creep on the nose infill material into the hollow. Thus, the increase in D in the hollow is higher than that on the other slopes; leading to an increase in slope failure potential. These results indicate that soil creep and slope failure act as infilling and evacuating processes of the zero order basin with differing intensities depending on slope form: soil creep removes soil materials from the nose and deposits them in the hollow, whereas slope failure removes materials from the side-slope and deposits them in the hollow. When infilling develops a sufficiently thick soil accumulation in the hollow, slope failure evacuates the hollow. (C) 1999 Elsevier Science B.V. All rights reserved.

The maximum glacial extent and depression of equilibrium line altitudes (ELAs) in the Hiunchuli massif of West Nepal were reconstructed by air photograph interpretation. The present glaciers are characterized by either of the following two types: steep valley or valley sided type. On the other hand former glaciers were large plateau glaciers with many radial outlets. During the maximum glacial extent, the lowest ELA lay at an altitude of 4, 100m, about 1, 000m below the present ELA and the area of the maximum glacial extent was 200 km2, some 200 times as large as the present one.