Description: As a result of the participation of R. V. "Meteor" in the International Indian Ocean Expedition during the winter 1964/65 altogether 37 sounding profiles were obtained in the Arabian Sea (plate 2-18). They are showing the topographic peculiarities of the main features of the sea bottom in this northwestern part of the Indian Ocean: Shelves, continental slopes and rises, deep-sea plains and hills, the Mid-Oceanic Ridge, fracture zones and seamounts. A control chart (plate 1) shows the geographical sounding lines. The coordination of the soundings with the bathymetric sketch and the map of physiographic provinces (B. C. HEEZEN and M. THARP) is represented in fig. 1 and 2. All soundings were obtained by the modern ELAC-Narrow Beam sounder which also accurately records very steep slopes of the sea bottom (fig. 3 and 4 ). Two series of sounding prnfiles (fig. 5 and 6) are showing the main topographic differences of shelf and slope between the eastern African and the western Indian continental margin. The descriptive analysis of all the sounding sections carried out by "Meteor" show the following main results: a) discovery of a very steep towering up seamount in the northern Somali basin at φ = 8° 16' N, λ 53° 12' E, which is rising up from a depth of 5000 m to about -2000 m (plate 3), b) registration of numerous steep canyons in the upper part of the eastern African continental slope near the coast of Kenya (plate 6 ), c) complete representation of a characteristic section across the Carlsberg-Ridge inclusively rift mountains and the Rift-Valley (plate 9), d) new characteristic results of sounding profiles across the Alula-Fartak trench showing very steep siopes on its flancs (plate 18).

Description: As part of the Atlantic Seamount Cruises 1967 with F.S. "Meteor" a topographic survey in the area of Great Meteor Seamount (φ = 30° 00' N, λ = 28° 30' W) was carried out from April 9th to May 1st and from May 31st to June 8th 1967. Shape and expansion of this seamount were generally known (fig. 1) but the form in detail was not yet identified by then. The length over all of the usable sounding sections with F.S. "Meteor" was 1930 nautical miles. Most of the track positions were taken by a relative reference system, that means a special navigation buoy with two radar reflectors (fig. 2). The echo soundings could be carried out with the ELAC Narrow Beam Sounder 1 CO ( extreme narrow-beam of ± 1,4° at 3 dB) giving an exact registration of even very steep slopes (fig. 3). As a result of the survey a detailed bathymetric chart of the Great Meteor Seamount could be designed ( original scale 1 : 250 000), here it is reproduced in a smaller scale (fig. 5). A model in 1:10 vertical scale exaggeration gives a general impression of the main topographical characteristics (fig. 4). It shows in the SW region of Great Meteor Seamount two other steep elevations discovered during the survey courses: Small Meteor Seamount (φ = 29° 41' N, λ = 28° 58' W) and Closs Seamount (φ = 29° 25' N, λ = 29° 08' W). Some typical sounding courses are represented in profiles (1:20 vertical scale exaggeration, fig. 6, table 1-8). Examples for slope inclination around the Great Meteor Seamount are given in a profile series exaggerated 1:10 (table 9). The Great Meteor Seamount consists of three morphological parts : a flat summit plateau (330 m - area about 1132 km2), steep slope (inclination about 13°, maximal 50°) and surrounding lower rise region (inclination 〈 5°). Terraces could be found in different depths at the steep slope of Great Meteor Seamount particularly at -450 m and - 550 m. Great and Small Meteor Seamount have the general shape of guyots or flattopped seamounts as described by HEss (1946), Closs Seamount shows the typical conic form of a submarine volcano. Small Meteor and Closs Seamount signify no terraces in their very steep slopes. The volume calculation based on the bathymetric chart gives the following rates : Great Meteor Seamount : 23842 km3, Small Meteor Seamount: 657 km 3, Closs Seamount about 212 km3.