Lake Kivu expedition : geophysics, hydrography, sedimentology (preliminary report)

In March 1971, seven members of the Woods Hole Oceanographic Institutionwere engaged in a multidisciplinary study of Lake Kivu. This expedition representspart of a long-range program concerned with the structural and hydrographicalsettings of the East African Rift Lakes and their relationships tothe Red Sea and the Gulf of Aden Rifts. The program started in May 1963 witha geophysical study on Lake Malawi (von Herzen and Vacquier, 1967). Severalexpeditions of our Institution into the Red Sea and Gulf of Aden area in 1964,1965 and 1966 (Degens and Ross, 1969) provided detailed geological informationon the "northern" extension of the East African Rift. And finally our study oflast year on Lake Tanganyika c1osed a major gap in the program; it allowedus to out1ine a model on the evolution of a rift which starts with (i) bulgingof the earth's crust, (ii) block-faulting, (iii) volcanism and hydrothermalactivity, and which has its final stage in (iv) sea floor spreading (Degenset al. 1971). In the case of Lake Tanganyika, only the second stage of thisevolution series has been reached, i.e. block-faulting. In contrast, the RedSea and the Gulf of Aden had already evolved to active sea floor spreading, almost25 million years ago. Somewhere along the line between Lake Tanganyikaand the Gulf of Aden must lie the "missing link" of this evolution series.Lake Kivu, almost 100 miles to the north of Lake Tanganyika is situatedat the highest point of the Rift Valley and is surrounded by active volcanoesand geothermal springs. As recently as 1944, lava flows reached the lakeshore. This lake was therefore, a natural choice to test our hypothesis onthe origin and development of rifts. Furthermore, the occurrence of largequantities of dissolved gases, e.g., CO2 and methane, represented an interestinggeochemical phenomenon worthwhile to investigate.

Supported by the National Science Foundationwith Grants GA 19262, GB 20956, and GU 3927;grants from the Petroleum Research Fund ofthe American Chemical Society PRF#1943A2;and by private research funds of the WoodsHole Oceanographic Institution.