The Earth is a planet of the Solar system. The Solar system is located in an arm of the spiral galaxy. The galaxy is a small member of the universe. Therefore, the formative field of the Earth should be discussed from a viewpoint of a part of the universal open system. The universe is composed of many levels of the hierarchy. They are atoms, minerals, rocks, planets, stars, galaxies and their groups from small to large. We examine whether the Sun and the Earth are unique existences or general ones in each level of the universal hierarchy. This examination should be the constraint of the prehistory of the Earth.
Some fossil periglacial wedges discovered in Hokkaido have been recognized as ice-wedge casts. We newly investigated dimensions, character and stratigraphy of 34 fossil periglacial wedges in northern and eastern Hokkaido, for the purpose of examining their origin (permafrost wedge or seasonally frozen ground soil-wedge). The origin of these fossil wedges is discussed on the basis of the relation between the depth and spacing of wedges and an activelayer thickness in the present permafrost region. Tephrostratigraphy and radiocarbon ages indicate that most of wedges have been formed during the latter half of the Last Glacial Age (ca. 42 ka-12 ka). The occurrence of fossil pollen and fossil woods indicating the boreal forest (especially Larix, Picea and Abies) and the opening of the thermal contraction cracks during this period suggest that the past annual variation in air temperature was characterized by warm summer and cold winter in northern and eastern Hokkaido. Then we calculated the annual air temperature amplitudes to be 15.8°C (northern Hokkaido) and 16.5°C (eastern Hokkaido) with the mean annual air temperature of-3°C corresponding to the limit of discontinuous permafrost zone, and to be 19.9°C (northern Hokkaido) and 20.9°C (eastern Hokkaido) with the mean annual air temperature of -7°C corresponding to the limit of continuous permafrost zone. On the basis of the annual air temperature amplitude and the mean annual air temperature, the active-layer thickness for different material was calculated by Aldrich's equation. The relation between the depth of the fossil wedges and the calculated active-layer thickness indicates that 9 fossil wedges among 34 have likely been permafrost wedges with the mean annual air temperature of -3 °C, 12 fossil wedges have likely been permafrost wedges with the mean annual air temperature of -7 °C others have been seasonally frozen ground soil-wedges. Our judgement on the origin of the fossil periglacial wedges suggests that northern Hokkaido (Okhotsuk Coastal Plain) and eastern Hokkaido (Syari Plain and Konsen-genya Plain) was located in the southern margin of the continuous permafrost zone or the northern margin of the discontinuous zone during the maximum cold stage of the Last Glacial Age.
Thermal infrared imageries of the LANDSAT Thematic Mapper (TM) band 6 are compared to the air temperature distributions and the geometry and materials of the urban area in Hiroshima City (132.5 °E, 34.4 °N), Japan, to extract the information on the urban heat island from the images. The results are summarized as follows : (1) Surface heat island is recognized on the LANDSAT TM nighttime thermal image taken at 21 JST on May 17, 1991. The distribution of brightness temperature matches closely with the air temperature distribution at 21 JST on MAY 19, 1992 (thermal image at that time was not able to be taken because of clouds). The discrepancy between air temperature and brightness temperature, recognized in the southern part of the city, can be explained well by the advection caused by the land breeze. (2) The daytime thermal images, which was taken at 10 JST on May 21, 1992, shows that brightness temperature at the central part of the urban area is low compared with the suburban area. The part of low temperature is also recognized in the air temperature distribution observed at the same time of the satellite overpass. (3) The distribution maps of height, surface area, volume and lot size of buildings are produced to compare the brightness temperature with the structure of the urban area. Brightness temperature is high along the major roads in the nocturnal thermal image. These parts correspond to the area where the buildings with high roof level, large lot size, large volume and large surface area are distributed. In these areas, daytime storage of heat and release of it at evening is considered to be important. (4) The interior of the blocks surrounding to the major roads shows relatively low brightness temperature. The area corresponds to the densely built-up area with low roof buildings or the open spaces such as school grounds and parks. Rapid radiative cooling in these areas is important to the formation of brightness temperature contrast in the blocks.
A geomorphological and pedological survey carried out in a fixed dune area of Niger, West Africa, revealed that (1) landforms consist of 8 major landform units such as plateau, hill-foot sand dune “sand epron”, pediplain, slope from pediplain to riverain plain, riverain plain, valley, sand dune, and inselberg and (2) each landform unit is characterized by particular soil types, divided into sandy and clayey soils. Sandy soils are derived from sand cover, and have an eluvial surface horizon and reddish brown subsurface ones. The degree of rubefaction in the soil profile is stronger on a hill-foot sand dune than on a pediplain. When the sand cover is thick, the rubefaction is stronger even on a pediplain. The sandy soil on riverain plain is eluviated almost completely, and becomes white sandy soil composed of quarts sand. Cultivated fields of pearl millet, the main crop in this region, are spread on the sandy soil area, especially at lower hill-foot sand dunes, pediplains with thick sand cover, riverain plains, and other sand dunes. The clayey soil develops on the plateau, the surface of which is covered by tiger bush. The soil fertility is quite low at any soils. Bare lands occur on plateaux without sand cover, upper hill-foot sand dune with thick sand cover, pediplains with thin sand cover, and slopes along temporal water way. The following four factors are critical for the land degradation : (1) thickness of sandy layer, (2) topographical position, (3) gradient of slope, and (4) surface crustability of soil. Even sandy soils form surface crust easily on the structureless surface horizon due, to some fine materials for crusting. The circular bare lands around termitaria are characterized by a harder surface crust due to fine materials translocated from a deeper horizon. The surface crust must inhibit infiltration of rain, which results in reduction of available water in the soil, and in dominant surface run-off. White sandy soils on riverain plain do not form the surface crust due to lack of fine materials while clayey soils on the plateau always form continuous surface crust. The “desertification” in the study area is a phenomenon related with depletion of sand cover. Therefore, in order to prevent “desertification”, how to manage sand cover must be studied seriously.
Major activities of andesitic/dacitic volcanoes are investigated by the thickness and areal dispersal of airfall tephra. In the field work, we often observe blackish soil sandwiched between two fall units of major eruptions. It seems that such soil represents environment including volcanogeneous materials and florae during the repose period of major activities. At the flank of Asama Volcano, we find a soil layer sandwiched with the 1783 and the 1108 tephra deposits. The historical record of eruptive activities of Asama Volcano prior to the 20 th Century documented major eruptions in 1108, 1532, 1596, and 1783. However, we find only the thick tephra depoists of 1108 and 1783. The purpose of this study is to find any trace of eruptive ejecta in the sandwiched soil and to presume the scale of eruptive activities between the two major eruptive episodes. The sandwiched soils were sampled at 19 localities ranging from 3 to 35 km distance from the summit crater along the major axis of the 1783 tephra deposit. The main results are ; 1) the thickness of the soil is correlated with the thickness of the overlying 1783 tephra. This fact indicates that the main parent material was supplied from the summit crater of Asama Volcano by frequent eruptions during 675 year period. 2) At some soil profiles, four layers are distinguished. Upper two layers are black and blackish brown in color contrasted with the lower two layers of dark greyish yellow and dark olive brown. 3) Bulk density of the uppermost layer becomes small with increasing distance from the summit crater, which indicates the abundance of pumice increases with distance from the summit crater. 4) The volume ratio of pumice increases exponentially with the distance from the summit. 5) The 3 rd and the 4 th layers are much abundant in pumice compared with the 1 st and the 2 nd layers, which implies the difference of eruptive type between them. 6) The eruptive acitivities during 675 years after the 1108 eruption is suspected to be much violent than the activities after the 1783 eruption. Considering the historic records, it is suspected that the soil of the 3 rd and the 4 th layers could have been formed by the eruptive products during 1108-1532, mostly in 1532. After 64 year quiescence, awakening of violent eruptive activities started with more explosice one. It may be the reason why the 1 st and the 2 nd layers are abundant in lapilli than the lower layers.
Plio-Pleistocene fluvial sediments are distributed in the hills along the western margin of the Kanto Plain. In this paper, the author reports its sedimentary environments at Hidaka City, Saitama Prefecture, namely, those of Yaoroshi tuff, Hanno gravel and their correlatives. The basement in this area (Chichibu Paleozoic and Mesozoic formations and Takaoka formation) is divided into three zones structurally by Koma-Hongo and Komagawa fault systems. And terrace deformation dipping toward the Kanto Plain is recognized on its surface. Yaoroshi tuff is in fault or unconformity contact with the basement in part of Koma-Hongo fault system. The vertical displacement of each fault system is over 50 m. Yaoroshi tuff is not distributed in west of Koma-Hongo fault system. Hanno gravel, conformably overlying Yaoroshi tuff, is in fault or unconformity contact with the basement. Hanno gravel and its correlatives were formed by old long rivers, of and the valley bottoms were at least 140 m above sea level in Koma River system area and at least 150 m above sea level in Shukuya River system area. Boulders of granite and diorite characterizing Hanno gravel in the south of Tenran-zan (Mt. Tenran) are not found in the investigated area. This fact suggests that the area was in different conditions of sedimentation from the southern area. The ridge directions of Koma Hills and Moroyama Hills had already settled before dissection proceeded. The gravel from Moroyama Hills and the adjacent areas is divided into the lower and the upper layers. The former is correlated with Yaoroshi tuff, while the latter with Hanno gravel. When Yaoroshi tuff deposited, forested stable land had extended widely. And short rivers flowing out from near mountains sometimes flooded and destroyed forests. After Yaoroshi tuff was formed, long rivers transported boulders with sands in large quantities from distant western mountains. These old long rivers kept their main courses to the present as Koma River system and Shukuya River system, and they mixed gravels by gathering currents and forming talus deposits.
The Futaba Group is the Lower Coniacian to Lower Santonian, fluvial to shallow-marine sedimentary succession distributed in the southern Abukuma Belt in north Honshu. Fifteen depositional facies were discriminated. They include alluvial fan, meandering river, braided river, transgressive lag and upper shoreface to inner shelf sediments. It is divided into three formations, the Ashizawa (the Asamigawa and Obisagawa Members), Kasamatsu and Tamayama Formations in upward sequence. Each formation consists of a third-order depositional sequence (DS). The first depositional sequence (DS 1) has a lowstand systems tract (LST) as the lower main part of the Asamigawa Member distributed in the northern half of the area. It is lithologically characterized by upper alluvial fan conglomerate and mid to lower fan sandstone and siltstone nonconformably overlying lower Cretaceous granite (sequence boundary 1 : SB 1). In the southern periphery of the distributed area the member contains talus or upper fan angular conglomerate. The upper part of the member distributed over the area is interpreted to be transgressive conglomerate with a sharp base called a ravinement surface (RS 1) which was formed by transgressive shoreface erosion. It may represent transgressive systems tract (TST). The following highstand systems tract (HST) is represented by the upper shoreface to inner shelf, medium to fine sandstone of the Obisagawa Member. The Kasamatsu Formation (DS 2) unconformably (SB 2) overlying the preceding depositional sequence (DS 1), is substantially characterized by fluvial upward-fining successions composed of channel sandstone and flood plain siltstone. The third sequence (DS 3) is characterized by thick fluvial (braided river) sandstone of the lower to middle part of the Tamayama Formation interpreted as LST and the upper shoreface to inner shelf sandstone of the upper Tamayama interpreted as HST. The sudden lithofacies change between the Kasamatsu and Tamayama Formations implies some large-scale changes in fluvial depositional systems by sea-level fall (SB 3). The transgressive conglomerate just above RS 2 in the basal part of the upper Tamayama Formation represents a thin TST. The upper sequence boundary (SB 4) of DS 3 shows the conspicuous clinounconformity between the Futaba Group and the Paleogene Shiramizu Group.
The article by Y. Ota and S. Odagiri (1994) on the age and deformation of marine terraces developed in Ashizuri area, Southwest Japan is welcome. Over the past several ten years a number of occurrences on the marine terraces ranged Holocene from late Quaternary have been reported in this area. Their article does not only make these important findings integrate on the successive time scale, but also shows the absolute age of terrace deposits by means of tephrochronology. However, there are some questions especially in the discussion on Holocene terraces. This short comment aims to submit the questions to the public. Those questions are summarized as follows ; 1. Some parts of discussion comes up without the description of Holocene terraces which were indicated in the preceding papers (Maemoku, 1988 and others). 2. Some of the raised landform which Ota and Odagiri described can not be considered as the evidence for Holocene coastal uplift judging from their depositional or geological condition especially in the highest level terrace. 3. Some of the interpretation on the age for Holocene uplift contradict themselves.