Okitsugu WATANABE* Okitsugu WATANABE, Masayuki INOUE and Shun'ichi KOBAYASHI

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1 2. Surface Conditions of the Ice Sheet Traversed in Observers: Okitsugu WATANABE* Okitsugu WATANABE, Masayuki INOUE and Shun'ichi KOBAYASHI The relief and slope of the ice sheet surface were observed along the routes traversed in trends of the prevailing winds on the ice sheet. They are re lated with each other depending on the Similar observations were carried out in the areas traversed in and (Watanabe and Ageta, 1972) Relief of the ice sheet surface Excepting a glazed surface, almost the entire surface of the Antarctic ice sheet is covered with such relief as dunes and sastrugi, reflecting climatic conditions such as the snow accumulation rate and katabatic wind characteristics at given place. Since the relief is formed by the depositional and/or erosional action of wind, it can be classified into two major types: dune formed by deposition of drifting snow, and sastrugi caused by erosion of preexisting dunes. Also, the long axis of both dune and sastrugi is presumed parallel to the direction of the wind which is the cause of their formation. The mechanism of the formation of these two types of surface relief was clarified by the studies of their structures. Morphology of the surface along the traverse routes was recorded completely by referring to stratigraphic analyses, and the observation results will be presented elsewhere Measurements of direction of surface re lief The directions of the long axis of the sastrugi and dune are shown in Table 1. Often two or three directions were found at a station. Same data collected along the route to the Yamato Mountains in ( Observer: Shun'ichi Kobayashi) are shown in Table 2. In these tables, both erosional and depositional surface reliefs are classified according to the category adopted by each observer. In Table 1, the directions of sastrugi, dune and erosional pit are given with remarks showing characteristics of occurence and form. In Table 2, erosional and depositional relief are classified into six categories; sastrugi, giant sastrugi and erosional pit (erosional) and barchan, dune and drift (depositional). these surface relief are given in terms of degree in true. The direction 5 of * Institute of Snow and Ice Studies, National Research Center for Disaster Prevention, Nagaoka

2 2.3. Surface slope Measurements of surface slope of the ice sheet were carried out along Routes H, I and J at 1520 km intervals when visibility permitted. By means of a Wild T2 theodolite, vertical angle of the surface against the theodolite horizontal plane was read for 8 directions starting from the magnetic north. The accuracy of angle readings was one minute. The maximum and the minimum inclinations of the horizon of the ice sheet and their azimuths are given in Table 3. Multiple maximum and minimum values on inclination, and/or disagreement of the downhill axis with the uphill were obtained when the surface topography was not simple. The mean direction of the surface slope was estimated from the distribution pattern of inclination around a station. The mean direction of a surface slope in Table 3 indicates the downward direction. The distribution of slope direction is shown in Fig. 1, where data obtained in a period from 1970 to 1974 are included. According to Fig. 1 the observed area can be divided broadly into three major subareas which are related to the drainage systems of the ice sheet. Reference Watanabe, 0. and Ageta, Y. ( 1972 ): Surface condition of the ice sheet in the Mizuho Plateau West Enderby Land area, East Antarctica, JARE Data Rep., 17 ( Glaciol. ),

3 Table 1. Direction or surface relief along Routes Y', I and J in *: predominant distribution, +: older formation Station Elevation Direction or Direction of number (m} erosional relief depostional relief S astrugi Erosion Dune I II III pit I II III y I

4 Station Elevation Direction of Direction of number erosional relief depostional relief (m) y Sastrugi Erosion Dune II III pit I II III ( I Route} I * * * * * * * 85* * * * * * 85*

5 Station Elevation Direction of Direction of number (m} erosional relief depostional relief Sastrugi Erosion Dune I II III pit I II III I * X as ao * * i * *

6 Station Elevation Direction of Direction of number (m) erosional relief depostional relief Sastrugi Erosion Dune I II III pit I II III I * * _ * * I *

7 Station number Elevation (m) Direction of Direction of erosional relief depostional relief Sastrugi Erosion Dune I II III pit I II III I * * * (J Route) J *

8 Station Elevation Direction of Direction of number (m) erosional relief depostional relief Sastrugi Erosion Dune I II III pit I II III J * * * * ooi X * * *

9 Station Elevation Direction of Direction of number (m) erosional relief depostional relief Sastrugi Erosion Dune I II III pit I II III J * * *

10 {Degress true) Station Elevation Direction of Direction of number (m) erosional relief depostional relief Sastrugi Erosion Dune I II III pit I II III J

11 Table 2. Direction of surface relief along Routes S, H, Z, X, A and C in (Degress tr ue) station Elevation Direction of Direction of number (m) erosional relief depositional re lief Sastrugi s Giant sastrugi Erosion pi t H Barchan Dune Drift s z ,

12 Station Elevation Direction of Direction of number (m) erosional relief depositional relief Sastrugi Giant Erosion Barchan Dune Drift sastrugi pit X , C

13 station Elevation Direction of Direction of number (m) erosional relief depositional relief sastrugi Giant Erosion sastrugi pit Barchan Dune Drift C A

14 (Degress true} Station Elevation Direction of Direction of number (m) erosional relief depositional relief sastrugi Giant Erosion sastrugi pit Barchan Dune Drift A s

15 Station number' H Table 3. Surface slope along Routes H. I and J. A positive/negative sign of inclination indicates an angle of elevation/depression. Surface slope Downhill Uphill Direction Inclination Direction Inclination (Degrees (Minutes) (Degrees (Minutes) true) true) , , Mean direction (Degrees true) I , , , ,

16 Surface slope Station Downhill Uphill Mean Direction Inclination Direction Inclination direction number (Degrees (Minutes) {Degrees (Minutes) (Degrees true) true) true) I o J

17 S ii Y A RAYNER 70 "/ l \ I. ff\ tt \.. 1,11. t. t t S H I R A S E \ 7SS EXPLANATION OF SLOPE VECTORS /. '\ t i \ ',_ //,,, \ The mean direction of surface slope Maximum inclination ( down hi 11 ) /',IA / Y' L P il t R T Fig. 1. Distribution of surface slope in Mizuho Plateau. 35

14.4 Simple Machines. The output of one device acts as the input of the next.

14.4 Simple Machines. The output of one device acts as the input of the next. The output of one device acts as the input of the next. What are the six types of simple machines? The six types of simple machines are the lever, the wheel and axle, the inclined plane, the wedge, the