HGM22-01

Room:101B

Time:May 26 15:15-15:30

Terrain classification of Southwest Japan including the Seto Inland Sea by object based
area segmentation
IWAHASHI, Junko1∗ ; MATSUSHI, Yuki2 ; FUKUOKA, Hiroshi3
1

GSI of Japan, 2 Kyoto University, 3 Niigata University

Terrain classification studies have been predominantly pixel-based using DEMs. Previously the corresponding author developed a pixel-based automated classification method of topography using slope gradient, convexity, and texture calculated froma DEM for small-scaled classification of plains, terraces, hills, mountains, and volcanos (Iwahashi, 1994; Iwahashi and Pike,
2007). However, a pixel-based approach could not handle scale issues or increasing noise associated with enlarging resolutionof DEMs. In addition, pixel data include problems of data volume and difficulties in spatial joining with attributes of thematic
maps.
Recently object based techniques for land-cover classification using color orthoimages or satellite images have become popular. In this presentation, the authors introduce the method of making terrain-type polygons by object-based software using a
combined image of geometric signatures. We produced a terrain classification map of Southwest Japan including the Seto Inland
Sea using a 150-m DEM which was a mosaic of land elevation and seafloor elevation. The terrain-type polygons were statisticallycompared with other thematic maps such as landslide distribution and lithology.
This study was carried out within a framework of ”Mapping of large landslides based on the sea-land combined terrain classification: case study of the overall Outer Zone of Southwest Japan including the Nankai Trough” which was a theme in ’2014
Collaborative Research with the Disaster Prevention Research Institute, Kyoto University’. We would also like to thank the Japan
Coast Guard who provided the 150-m and 450-m Geographical Feature Meshes Data of Southwest Japan.
References
Iwahashi, J. (1994):Development of landform classification using digital elevation model. Disaster Prevention Research Institute annuals (Kyoto Univ.), 37(B-1), 141-156. (in Japanese with English abstract and figures)
Iwahashi, J. and Pike, R. J. (2007):Automated classifications of topography from DEMs by an unsupervised nested-means
algorithm and a three-part geometric signature.Geomorphology,86,409-440.

Keywords: Fundamental Geospatial Data, seafloor topography, object based area segmentation, DEM, terrain classification, Seto
Inland Sea

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HGM22-02

Room:101B

Time:May 26 15:30-15:45

Relation between tectonic uplift rates and erosion rates in the Kiso Range from in situ
cosmogenic nuclides
NAKAMURA, Atsunori1∗ ; YOKOYAMA, Yusuke1 ; FUJIWARA, Osamu2 ; HORI, Kazuaki3 ; MIYAIRI, Yosuke1 ;MATSUZAKI, Hiroyuki4
1

Atmosphere and Ocean Research Institute, University of Tokyo, 2 Geological Survey of Japan, AIST, 3 Department of Geography, Nagoya University, 4 The University Museum, University of Tokyo
Tectonic uplift enhances the elevation and local relief of mountain ranges (Willett and Brandon, 2002). High relief leads to intensified erosion process through the slope dependent surface processes namely as relief becoming steeper larger erosion process
is resulted (Ahnert, 1970). Therefore, documenting rates of uplift and erosion is critical for understating how topography of themountains is maintained by such a negative feedback. In case of continuous rock uplift, numerical models of landscape evolution
suggest that mountain ranges may reach steady states in which uplift rates and erosion rates are balanced, and hence elevationand topography may be maintained (Molnar and England, 1990). In this study, we present erosion rates reconstruction from thedrainages of the Tenryu River using terrestrial cosmogenic nuclides (TCN) in order to document their relations to the topographic
evolution of the Kiso Range (central Japanese Alps). Measurement of TCN allowed us to determine the erosion rates over thetimescale of 103 year. We sampled river sediments from the tributaries and the main stream of the Tenryu River. Basin-averaged
erosion rates of the tributaries near the main ridgeline of the Kiso Range are 1000-2000 mm/kyr, whereas the southern tributaries
have lower erosion rates between 600 and 1000 mm/kyr. In addition to the samples from the modern riverbed, sediment samples
were also collected from the drilling cores excavated near the mouth of the Tenryu River in order to reconstruct paleo-erosion
rates. Erosion rates using TCN from the core samples show relatively constant erosion rates through the Holocene. Furthermore,
previously reported erosion rates using sediment yields (Kawata and Uemoto, 1998) and apatite fission track ages (Sueoka et al.,2012) suggest constant erosion rates of the Kiso Range over 50 yr, 1 kyr, and 1 Myr time scales. These values are comparablewith the uplift rate of the Kiso Range (Ikeda et al., 2002), and hence the topography of the range in the central Japan is maintainedin a steady state.

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HGM22-03

Room:101B

Time:May 26 15:45-16:00

The limit of the geomorphology learning in high school geographical B
AOKI, Kunihiro1∗
1

Nihon Univ. BUZAN High school & junior high school

At most 12 units per 3 years of geography B could be taken in the curriculum which is being put into effect from the previous
fiscal year. I even put emphasis on learning of physical geography more than now and am teaching. But the limit has caused thegeomorphology with which I deal geographically and the geomorphology with which I deal by earth science in the explanation
in a cause different in a viewpoint or the field of the geomorphology and the industrial geography.
It’s introduced about the learning contents of geomorphology in a main school by this announcement. And I’d like to receive
advice for teachers.
I’m thinking it’s to increase the contents of geomorphology that I’m thinking, and understanding in the whole geography
deepens. It’s esteemed to deal with the reason that fact is explained, not to handle only to appear in a textbook. The following
problem has formed by the current state.
1. There is a student going to memorize the distribution of the submarine ridge and the trench. When doing talk of ”terrestrial
heat flow ”, I’m thinking a logic can be grasped.
2. By geography B, crustal alteration, ”plate tectonics”, only, to explain, the whole tectonics theory can’t be fingered. Therefore
the limit occurs to the in-depth explanation motive power.
3. The volcanic contents end only by a volcanic stereotype because you can’t touch about developmental process of a magma.
Mode of eruption and a volcanic ejecta don’t also touch, so talk of a produced mineral can’t be done. At the same time, a reason
and a distribution area of produced resources can’t be explained.
4. Only the case that those tomography exists can finger fold and a fault, and a word as lineaments doesn’t exist in a textbook.
Therefore the significance from which fold and a fault are learned becomes indefinite.
5. The learning which surveys a physical environment in each geologic age is needed. This would like to make them learn toreflect production of resources and the present physical environment.
On the convenience with the restrictions of curriculum guidelines and the case that I organize the contents and teach freely
are difficult, but I’d like to ask the education technique which esteemed geomorphology and education contents because it’s theentrance where a geography is learned to learn geomorphology.

Keywords: geomorphology, geography, geography B

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HGM22-04

Room:101B

Time:May 26 16:15-16:30

Slope failure of the Oya-Kuzure and generation of the Akamizu Fall, upper reaches of the
Abe River, Shizuoka Prefecture
SHIRAI, Masaaki1∗ ; WATANABE, Mayo1 ; UTSUGAWA, Takako1 ; HAYASHIZAKI, Ryo1 ; TAKAHASHI, Takayuki1 ;OBI, Ryo1 ; KATO, Yuma1
1

Dept. of Geography, Tokyo Metropolitan Univ.

The “Oya-Kuzure” slope failure is located in the source area of the Abe River, Shizuoka Prefecture. It is estimated that many
failure events had occurred repetitively around the area (e.g., Machida, 1959). The latest large-scale failure is estimated as
occurring early 18th century. Deposits originated from the 18th century failure filled the Oya River and upstream of the Abe
River (e.g., Tsuchiya, 2000).
Although origin of the Akamizu Fall, which is located on main stream of the Abe River with a height of 60 m has been inferredas that stream of the river eroded debris flow deposit filling the valley, that stream of the river flowed across a ridge, and so on,
any opinion does not show evidence sufficiently.
As a result of survey, it were confirmed that distribution of debris flow deposits and paleo-current estimated from direction ofgravel imbrication in the deposits imply meandering of the Abe River valley before burial by debris flow deposit. In addition,
channel of the fall across a ridge of basement rock. We concluded that filling of a valley by debris flow deposit caused shortcutof stream of the Abe River across a ridge and generation of the Akamizu Fall.

Keywords: debris flow deposit, shortcut, Abe River, Akamizu Fall, Oya-Kuzure

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HGM22-05

Room:101B

Time:May 26 16:30-16:45

Landform, debris transport processes and sediment budget in the Dakesawa valley, Northern Alps, central JapanSHIMAZU, Hiroshi1∗
1

Rissho University

The Dakesawa valley is originated in the Mt. Oku-Hotakadake (3190m) and runs down into the River Azusa at the elevationof 1500m. The middle part of the valley is covered with debris which is supplied from the valley side slopes. To discuss thedebris transport processes and sediment budget I investigated the characteristics of the valley floor deposits and valley floor landforms. On the middle of the valley bottom, the elevation is between 2180m and 1730m, there are thick unvegetated deposits.
The average slope of middle part of the valley floor is 30%. There is no flow water on the valley bottom, because of infiltration
to the deposits. From the valley side slope debris are supplied forming talus cones. Erosional scars along the valley floor show
debris of the valley floor are originated from the talus cone deposits. Decrease of the size of the valley floor deposits from 3m to
0.5m shows debris transport with sorting process. Debris transported from the upper and middle part stopped entering the forest
area. The lower part are filled with huge blocks of talus deposits and debris flow sediments supplied from valley side slopes.
Above-mentioned debris closed the outlet of the Dakesawa valley. The upper and middle part deposits cannot reach the lower
end of the Dakesawa valley, bordering on the floodplain of the River Azusa. Thus, present day sediments are being accumulated
in the valley floor and few sediments flow into the River Azusa.
Keywords: landform, valley floor, debris transport process, sediment budget, Dakesawa, central Japan

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HGM22-06

Room:101B

Time:May 26 16:45-17:00

Natural dam constructions and breaks at the Oshika and the Mitoku River, Misasa-town,
Tottori southwest Japan
KODAMA, Yoshinori1∗ ; OKAZAKI, Shiho2
1Fac. Regional Sciences, Tottori Univ., 2 Undergraduate, Fac. Regional Sciences, Tottori Univ.

Four terrace-like deposits caused by deep seated landslides were known at the lower part of the Oshika River in Misasa, Tottori,
south-west Japan. Another similar terrace-like deposit seems to be at the middle part of the Mitoku River in Misasa, which isneighboring north of the Oshika. These five landslides seem to be related to earthquakes caused by the Iwatsubo active fault,
which runs in the eastern part next to the Oshika and the Mitoku river basin. The objectives of this study are to clarify whether
natural dams were constructed or not, and if there were natural dams, how the dams were broken down.
We conducted topo-map reading to make distribution map of terraces and their longitudinal profiles projected along the river.
We did also hand borings to get soil samples in order to measure radioactive carbon datings. In the field, we observed terrace
deposits.
At three sites out of the five landslides, natural dams were formed judging from reservoir silty-clay deposit at Sengenbara,
Mitoku, or steep gradient (1/8 at Kannokura, 1/13 at Nishioshika, in the Oshika) terraces distributed just downstream-side of thedams in 1.2 to 1.4 km long. Large andesite boulders (ca.1 to 2 m in diameter) were observed as deposits of these dams.12 Carbon
14 dating values showed the followings: i) deep seated landslides occurred at three different times: 34,000 yr ago at Nishioshika
and Mogura, 10,300 yr ago at Sengenbara, and 1,200 yr ago at Kannokura. These large landslide events suggest that the Iwatsubo
active fault moves at about ca.10,000 yr intervals and successive intensive rainfall caused landslides. ii) Natural dam broke inmany batches and the reservoirs maintained for longer times: 400 yr or more at Kannokura, 8,000 yr or more at Sengenbara, and
30,000 yr at Nishioshika. We need datings of Higashioshika landslide event.
Keywords: natural dam, out-burst flooding, deep seated failure, fluvial terraces, radioactive carbon chronology, Iwatsubo active
fault

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HGM22-07

Room:101B

Time:May 26 17:00-17:15

Landform development of bedrock river focusing on the planform : Laboratory experiments
TSUZUKI, Yuuki1∗ ; ENDO, Noritaka1
1

Graduation School of Natural Science and Technology, KU

Generally, development of fluvial landform is known to be strongly affected by surface slope, climate and tectonics. In fieldstudy, it is necessary to take accounts of developmental stage of individual rivers when discussing relations between various
factors and landforms, because we need distinguish between spatial and temporal variations. In this study, we conducted flume
experiments focusing mainly on temporal (developmental) change of bedrock river. The flume was about 1 m square and a weirwith a slit at the center was installed at the downstream end to prevent change of base level during the run due to uncontrolled
sedimentation. Parameters discussed in this study are initial surface slope, precipitation and tilting rate. Findings are as follows.
Temporal increase of drainage area occurred through two stages, which is considered to correspond to the formerly reported
two-staged development of channel network. Unlike temporal change of drainage area (drainage area vs. time), the relation
between drainage area vs. trunk-steam length for each data of different time in an identical basin fell on a single power function.
Number in the range of these functions obtained in this study, was n = 0.38 ˜0.83. The drainage basin under smaller precipitation
had a power number (power-law exponent) larger than 0.5, meaning that the basin became elongated longitudinally with its
development, which is considered to be because tributaries could not grow largely and laterally owing to smaller precipitation.
The drainage basin neighboring a larger basin had also a power number larger than 0.5, which can be attributed to suppressionof later growth of basin due to small influx of water.
Keywords: laboratory experiment, bedrock river, precipitation rate, drainage area

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HGM22-P01

Room:Convention Hall

Time:May 26 18:15-19:30

Landforms and Vegetation of Limestone Area in the Northernmost Part of the Suzuka
Mountains
YAMAUCHI, Hiroyuki1∗ ; UMITSU, Masatomo2
1

Graduate School of Geography, Nara University, 2 Department of geography, Nara University

Objective of the study is to make clear the relationship between the karst landforms and vegetation in the area of Mt. Ryouzen
summit, Shiga prefecture. Geology of the study area mainly consists of limestone. And the karst landforms of the study area arecharacterized as the karrenfeld and doline. Mountain slopes in the study area are classified and mapped. And the distribution of
the dolines was plotted on the map. The shape of dolines in the area was classified into 4 types from the viewpoint of existence ofbottom flat and the inner slope condition. Characteristics of the vegetation in the study area are generally related to the conditionof mountain slopes. Woody vegetation is distributed in the area of gentle slope, and herbaceous plant mainly distributes in thesteep slopes of the region.Distribution of plants on the inner part of the doline wall is related to the direction of the inner wall.
Vegetation of the north-facing slopes is characterized by low grasses. In the slopes and bottoms of doline, vegetation is generally
sparse or barren condition.

Keywords: karst landform, Mt. Ryouzen, doline, slope, vegetation

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HGM22-P02

Room:Convention Hall

Time:May 26 18:15-19:30

Geomorphological study of the volcanic mud flow in the Fukushima basin
SETO, Masayuki1∗ ; NAKAMURA, Yosuke1
1

Fukushima University

This paper examined the damage of the volcanic mud flow by the Azuma-yama volcanic eruption. From Azuma-yama, theriver are flowing eastward. It seems that a mud flows go down these rivers. For this study, we drew the topographic map basedon DEM data. We clarified the range of a mud flow, and the position of the river from this map.
Next, we drew three longitudinal sections of the river which flows into the Fukushima basin from the Azuma-yama volcano.
The distance to the Fukushima basin changes greatly with river channels. The arrival time to the Fukushima basin of a mud flowchanges with channels. There are three patterns in channels. (1) After going to north, there are channel which changes direction
to the east. (2) There is a channel which flows to the east directly. (3) After going to south, there are channel which changes
direction to the east. Distance is greatly different by these three patterns. So, the location of a crater is very important because ofdisaster prevention.
Furthermore, we drew the cross section inside the Fukushima basin.The cross section shows concave form.The cross section
has a 60 m depth. A mud flow may concentrate on this hollow. It is necessary to take this geomorphic feature into consideration
for anticipation of damage. This study revealed that the channel passage and geomorphic features will influence the damage ofvolcanic mud flow strongly in Fukushima basin.

Keywords: mud flow, channnels, Azumayama volcano

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HGM22-P03

Room:Convention Hall

Time:May 26 18:15-19:30

The geographical disasters in Shirouma Daisekkei valley , the Northern Japanese Alps.
SATOH, Shino1∗ ; NARAMA, Chiyuki2
1

Department of Environmental science , Niigata University, 2 Niigata University

Shirouma Daisekkei valley, which is located in the northeast of the Northern Japanese Alps is the largest snow patch of Japan.
More than 10,000 climbers pass during every summer. In this valley, rockfall, landslip, debris flow, and snow avalanche cause
climbing accidents every year. In this study, we researched rockfall and remobilization of fallen stones in Shirouma-Daisekkei,
using field data such as air temperature, surface ground temperature, interval camera, GPS measurement, distribution of rock andgeomorphological data of DEM.
Two interval camera shows many rocks on the snow patch appeared by melting snow during July?August. The number of fallenstones on the snow patch was little. Surface ground temperature and air temperature show rockfall caused by freeze-thaw hardly
occurs in this period. Although remobilization of fallen stones on the snow patch was known, the distance of remobilization was
up to 50 m between end of July and end of August. The small movement of fallen stones was confirmed every day. The slope
degree is around 25 degree or less on the main Shirouma-Daiisekkei valley. On the other hand, No. 2 and No. 3 snow patches oftributary valleys are between 26 degree and 40 degree. The steep slope of the No. 2-No. 3 snow patches might be largely related
to rockfall accident during this period.

Keywords: Shirouma Daisekkei valley, rockfall, snowpatch, geographical disasters

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HGM22-P04

Room:Convention Hall

Time:May 26 18:15-19:30

Shapes and origins of notches and caves on sea cliffs, the Noto Peninsula, central Japan
KOBAYASHI, Wataru1∗ ; HAMADA, Masaaki1 ; YAMAGUCHI, Hiroyuki2 ; TAKAYAMA, Toko3 ;ISHIGAMI, Shintaro4 ; HIRAMATSU, Yoshihiro5
1

Hokuriku Electric Power Co., Ltd., 2 Natural Consultant Co., Ltd., 3 Asia Air Survey Co., Ltd., 4 Hokuden Engineering Consultants Co., Ltd., 5 Kanazawa University
In the Noto Peninsula, there are many notches and caves on sea cliffs. Their major origins may be salt weathering and wave
erosion, but few detailed studies have been carried out in the past. A level of wave-cut notch indicates a paleo-sea level, and isuseful to estimate uplift rates of the area. Therefore we aimed to classify them into notches and caves formed by wave erosion
and those formed by other processes such as salt weathering in this study.
We studied coasts of the Noto Peninsula, and carried out 3D laser scan survey in western coasts where these features are abundant. We obtained red relief image maps which show detailed topographic features of the sea cliffs from DSM (Digital Surface
Model) data taken by a laser scan survey to recognize the caves and notches. We also performed geological survey and X-ray
diffractometry analysis to determine their origins.
We recognized many caves and notches on sea cliffs composed of Miocene volcanic rocks in western and northern coasts of
the Noto Peninsula. In western coasts, Their shapes are classified roughly into two types, linear type and ellipsoid or polygonal
type. The former includes vertical, horizontal, and oblique continuous shapes, of which sizes are less than a meter in width.
Some of them observed at an altitude of 2 meters in several areas show the scale of a meter in width and horizontal continuous
shapes with benches at their base, indicating that they were formed by wave erosion. The caves of the latter are distributed widelyover cliffs, and they are dozens of centimeters to several meters in diameter. The occasional existence of white powder, whichis composed of gypsum (CaSO4 • 2H2 O) according to X-ray diffractometry analysis, in caves of the latter, indicates that salt
weathering is closely related to the formation of this type.
Assuming that wave-cut notches recognized in this study were formed at the same stage, uplift rates of western coasts of theNoto Peninsula are equal after their formation. Therefore it is necessary to determine the age of their formation.

Keywords: the Noto Peninsula, sea cliff, 3D laser scan survey, topography analysis, wave erosion, salt weathering

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HGM22-P05

Room:Convention Hall

Time:May 26 18:15-19:30

Transport processes during MIS 5.1 and MIS 3 to 2 estimated from fluvial terrace gravels
in Tama and Sagami rivers
TAKAHASHI, Takayuki1∗ ; SHIRAI, Masaaki1
1Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University

Fluvial terrace sediments are formed by depositional process of rivers in the past, therefore it may be possible to infer the
paleo-river transport processes and the paleo-climate from terrace sediments. To reveal the differences of the river transport
processes between MIS 5.1, which is a relative warm period, and MIS 3 to 2, which is a relative cold period, this study examines
the change in size and roundness on gravels of fluvial terraces.
Field survey was conducted at Musashino 2 terrace (M2 terrace; MIS 5.1) and the Tachikawa 2 terrace (Tc2 terrace; MIS 3to 2) in the fan region in the Tama River, and at the Sagamihara 3 terrace (Sg3 terrace; MIS 5.1) and the Tanahara terrace (Thterrace; MIS 3) along the Sagami River around the fan apex in the Sagami River. The mean maximum gravel size and the meanroundness were obtained from the long axes of the 10 largest gravels and 50 gravels, respectively. The distance from the fan apex
and the mean slope of the terraces are obtained from 5m mesh DEM published from Geospatial Information Authority of Japan.
Because the Tama and Sagami rivers are estimated to have been under similar scale and paleo-climate conditions, we attempted
to explain uniformly the changing trend in the mean roundness of both rivers. As the results, it is estimated that the roundness of
MIS 5.1 gravels increases at downstream reaches than that of MIS 3 to 2 gravels.
If the production of fine gravels is active, which is made by crushing, fine gravels should be angular. Conversely, if the
production of gravels is inactive, fine gravels which tend to be transported longer distance should be rounded. Relationships
between the size and roundness of the measured gravels of mountain region and fan region in the Sagami River suggest that atransport process accompanying with large gravel crushing was active in MIS 5.1. Postulating that gravel crushing occurred bydebris flows, it is suggested that the effect of debris flows from tributaries was active during MIS 5.1 than during MIS 3 to 2.

Keywords: fluvial terrace, terrace gravels, Tama River, Sagami River, debris flow

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HGM22-P06

Room:Convention Hall

Time:May 26 18:15-19:30

3D DEM generation from digital aerial photographs considering the influence of vegetation
ENDO, Ryo1∗ ; SUGAI, Toshihiko1
1

The University of Tokyo

High-resolution topographic data has been generated in Japan according to development of surveying technique. In particular,
DEM (Digital Elevation Model) made from LiDAR data is used in various fields. However, topographic data of mountain area islower in accuracy than that of plain since LiDAR survey is not conducted well in mountain area. Therefore, there are few maps
which micro-topography such as scarp or crack is correctly represented on (ex. Yagi et al., 2003; Sato et al., 2004).
Recently, combined technique of Sfm (Structure from motion) and MVS (Multi-View Stereo) has applied to generation of
DEM from digital aerial photographs (ex. Uchiyama et al., 2014). Using this technique, we try to generate 3D DEM from GSI
digital aerial photographs. One of the most important problems is to remove vegetation from 3D model. In order to minimize theerror of removing, we select Kiso Mountain Range as a test field.
The method of this study includes extraction of vegetation area, mask of vegetation area of aerial photographs and, generationof DEM using Sfm-MVS software. NDVI (Normalized Difference Vegetation Index) is an index which is often used to extract
vegetation from satellite image. In order to extract vegetation not from satellite image but from digital aerial photographs, anindex 2G RBi (Richardson et al., 2007) is introduced. Correlation between NDVI and 2G RBi are calculated from Landsat
satellite image and threshold between vegetation and the others is decided. After masking vegetation area in aerial photographs,
ortho photo and 3D DEM are generated using Agisoft PhotoScan.
In this presentation, we will discuss the DEM and its precision.

Keywords: digital aerial photograph, DEM, ortho image, vegetation, NDVI

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HGM22-P07

Room:Convention Hall

Time:May 26 18:15-19:30

Geomorphic analyses in Bor mining area, Serbia.
WAKASA, Sachi1∗
1Faculty of International Resource Sciences

Geomorphology around Bor mining area, east of Serbia was analyzed. Using Geophysical information was 1:25000 and
1:100000 topological image maps, CAD maps, ASTER-GDEM and high definition satellite images. Channel system andunderground-openness (Yokoyama et al., 1999) were analyzed and these maps were combined ASTER-GDEM to make ascent map. On the other hand, land-cover data were estimated from high definition satellite image analyses and spectrum analyses
of waste rocks. Obtained data will be reported in this meeting and used to select environmental observation points. Using
environmental observation data, geochemical map will be made.

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HGM22-P08

Room:Convention Hall

Time:May 26 18:15-19:30

Evolution of the Gonghe Basin, northeastern Tibet, constrained by in situ cosmogenic
radionuclides
SHIRAHAMA, Yoshiki1∗ ; MIYAIRI, Yosuke2 ; HE, Honglin3 ; KANO, Ken-ichi4 ; OKADA, Shinsuke5 ;YOKOYAMA, Yusuke2 ; IKEDA, Yasutaka1
1

Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 2 Atmosphere and Ocean
Research Institute, The University of Tokyo, 3 Institute of Geology, China Earthquake Administration, 4 Center for Integrated
Research and Education of Natural Hazards, Shizuoka University, 5 International Research Institute of Disaster Science, Tohoku
University
Tibetan plateau has been growing up by the collision between Indian and Eurasian Plate and expanding its area laterally by
the marginal deformation of the plateau. However, the growth mechanism has been highly debatable. Gonghe Basin at thenortheastern margin of the plateau is about 3200 m above the sea level and bordered by Qinghai Nan Shan and Heka Shan on
the north and south, respectively. Gonghe Basin was filled with over 500 m thick sediment transported by the Yellow River.
Subsequently, the river formed many fluvial terraces while cutting it down. Understanding these processes of sedimentationand later erosion in the basin is an important key for revealing the lateral growth of the plateau. They, however, have not been
understood in detail. In order to reveal these processes we applied detailed geomorphological mapping and analyses by in situ
cosmogenic radionuclides (CRNs). Our geomorphological mapping by satellite images and digital elevation model show that
there are seven steps of fluvial terraces from T1 to T7 and four steps of lacustrine terraces from L1 to L4 in descending order.
Our field work revealed that the L1 surface, which is the top lacustrine terrace, is covered with loess of 2-3 m thick including
three layers of paleo-soil. This fact indicates that the top lacustrine terrace experienced at least three inter-glatial periods. To
decide abandonment ages of lacustrine and fluvial terraces by CRNs concentrations we collected some subsurface samples from
L1, T2, and T3. In addition to this, crastic sediments, which fill the basin thickly, were collected at nine points per 50 m depth
from the fill top surface to the bottom of the valley for estimating burial history. In this presentation, we will introduce someresults of CRNs analyses and their implications in evolution of the basin.
Keywords: Tibetan Plateau, Qaidam Basin, tectonic landform, in situ cosmogenic radionuclide

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HGM22-P09

Room:Convention Hall

Time:May 26 18:15-19:30

Dating the marine terraces in Southern Wakayama and Southwestern Kochi using in-situ
cosmogenic nuclides
NAGANO, Gen1∗ ; YOKOYAMA, Yusuke1
1

Atmosphere and Ocean Research Institute, The University of Tokyo

Marine terraces are low-relief platforms located along coastal areas. They are formed by waves action with the changes in
the relative sea level (RSL) that is affected by combined effects of the eustatic sea level (ESL) and the tectonic movements (e.g.
uplift, subsidence and isostatic effect). Therefore, determining the ages and the elevations of the marine terraces allows us toreconstruct the ESL and/or the tectonic history of the study area.
Along the south coast of Japan, particularly at the Kii Peninsula and the southern coast of the Shikoku Island, there exist
relatively well-preserved marine terraces. They are now located at the high elevation of ca. 50?100 m, and hence regarded as
the suitable counterparts to reconstruct uplift history of the south coast of Japan. However, the ages of these terraces are poorly
understood due to the lack of the ash layers that is suitable for the tephrochronology. Here we determine the age of the marine
terraces using terrestrial in-situ cosmogenic radionuclides (TCN). This is the first age estimation of the marine terraces in Japan
using TCN. Concentrations of TCN in surface rocks have been used for dating the marine terraces in the arid region where
negligible erosion is taking place.
The study sites are the Kii Peninsula, Wakayama and the Ashizuri Cape, Kochi, located along the Nankai Trough where thePhilippine Sea Plate is subducted under the Eurasian plate. There are several well-preserved marine terraces along the coastalline since the uplift rates of the study area are high owing to the tectonic setting.
Some previous studies tried to estimate the crustal uplift with seismic activity in the Nankai Trough. However, a few studies
directly determined the formation age of the marine terraces. We determined the exposure ages and erosion rates in these areasfrom concentrations of in-situ cosmogenic nuclides.

Keywords: in-situ cosmogenic nuclides, marine terrace, erosion rate

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Room:Convention Hall

Time:May 26 18:15-19:30

Pangea was a planet
MADO, Shinichiro1∗
1

MAROSA
1. The Problem

Alfred Wegener had an idea that the unique super continent called Pangea suddenly broke into pieces called continents, which
moved along the surface of the Earth.
However, next two major questions were not solved:(1) Why the super continent Pangea was suddenly broken into pieces?
(2) What kind of force moved the continents?
After Wegener, the theory of plate tectonics prevails, which attributes the force moved the continents to an analogy with thermo
fluid dynamics. However, introducing such idea brings about many contradictions.
In this paper, we show you a new theory of planetary impact (Mado 2010), which is able to answer these two questions, is also
supported by the real landforms of the current Earth.
2. Continental Drift, Plate Tectonics, Planetary Impact
The theory of continental drift have above two major problems.
The theory of plate tectonics tried to solve the second problem by analogy with thermo liquid dynamics, though it was not able
to solve the first problem at all.
It also have a significant mistake in its theoretical basis of aging the oceanic floors. Shinichiro Mado detected two major
misunderstandings about oceanic floor aging:(1) It has a misunderstanding in creating mechanisms of stripes of geo-magnetic anomalies (Mado 2013), and(2) It has also a misunderstanding in aging the seabed by aging sediments immediately above the seabed, because of neglecting
the effects of seawater increase (Mado 2014).
Therefore, plate tectonics should be rejected.
The only one remaining theory is the theory of planetary impact (Mado 2010). The theory solves both of above two problems
rationally and persuasively.
3. Landforms created by curvature adaptations
Landforms created by two types of curvature adaptation (Fig.,1 Fig.2, Fig.3) are evidences of the fact of the planetary impact.
3-1. Arabian Peninsula, Indian Peninsula, Indochina
These three peninsulas had been joined in one piece before it was torn into three by the curvature adaptation (Fig.4, Fig.5)
after the planetary impact. If the neighboring edges of these three peninsulas were put over the next edge, these three peninsulas
would make up a dome like three-dimensional landscape. This is the proof of the fact that a ball shaped object was broken into
pieces and torn to make up the current landforms.
3-2. Himalayan fold mountains
The surface of the broken ball shaped object had a greater curvature than the surface of the Earth. Therefore, when the rocks
inside the pieces went down into the Earth by the gravity, wrinkles was created on the surfaces of the pieces (Fig.3). This is thereason of the creation of Himalayan fold mountains (Fig.6, Fig.7). Himalayan fold mountains are the evidence of the curvatureof the surface of the broken ball shaped object being greater than the current Earth.
4. The Solution(1) The question, why Pangea was suddenly broken into pieces, will be answered, if we suppose Pangea was a planet which
made an impact on the other planet to get into one new planet the Earth.
(2) The question, what kind of force moved continents, is answered, if we suppose the force was the gravity. That is, (a) the

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Time:May 26 18:15-19:30

impact was caused by the gravity between both planets collided, and (b) the impact broke into pieces one of these planet, and (c)the force, that moved the pieces along the surface of the other planet rather unbroken, was caused by the impact.

Fortunately, the theory of planetary impact has been demonstrated by the landforms on the surface of the current Earth.
5. Reference[1] (Mado 2010) Shinichiro Mado, On the Cause of the Continental Drift, SIT043-P01, ABSTRACTS, Japan Geoscience
Union Meeting 2010.
[2] (Mado 2013) Shinichiro Mado, It was not switching global geo-magnetic fields that created the alternating anomalies overoceanic ridges, SEM36-P01, ABSTRACTS, Japan Geoscience Union Meeting 2013.
[3] (Mado 2014) Shinichiro Mado, The Ocean Floor was Expanded by
Increasing Seawater, SCG67-P01, ABSTRACTS, Japan Geoscience Union Meeting 2014.

Keywords: continental drift, plate tectonics, planetary impact, Arabian Peninsula, Indian Peninsulas, Indochina, Himalayan fold
mountains, Pangea

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