The Bouguer anomaly map of the rift zone south of the southernrnend of the Main Ethiopian rift between Lat. 4Â° OO'N .;; 7Â° OO'Nrnand Long. 36Â° 00 I E - 39Â° 45 ' E is presented. The computed Bouguerrnanomaly map shows a complex pattern of positive and negativernBouguer gravity anomalies. A positive Bouguer gravity anomalyrnof -165 mGal occurs over the floor of the Abaya-Chamo rift andrnis flanked by negative anomalies that reside on its shoulders.rnThe anomaly pattern associated with the Chew Bahir rift isrncompletely different from the other regions. The floor has arnnegative gravity anomaly of magnitude -135 mGal and is flankedrnby positive gravity anomalies residing on its shoulders. Thisrnmay be attributed to the swamp and volcano-Iacostrine nature ofrnthe rift floor. Further south in Kenya, the Bouguer anomaly maprnshows that there is a relative increase in magnitude of thernregional gravity field with a complex pattern of alternatingrnpositive and negative anomalies which are generally oriented arnNNW-SSE and E-W direction.rnTwo profiles that run through the major tectonic systems (thernAbaya-chamo rift and the Chew Bahir rift) of interest in thernarea were extracted from the Bouguer anomaly map. 2%-0 gravityrnmodels were constructed along these profiles. The results ofrnthe model calculations are that:rnAlong Profile AA, the crust beneath the plateaus is 35 to 40 kmrnthick. within the axis of the Abaya-Chamo rift the crust thinsrnto 29 km. Along profile BB, the crust beneath the high lands inrnthe vicinity of the Amaro horst is 35 to 40 km thick. Beneathrnthe rift zone, i.e., the floor of the Chew Bahir rift and thernflanking uplifted regions the crust thins to 27 km. Thernobserved crustal thinning beneath_the rift zones along bothrnprofiles is thought to be caused by an upward progression ofrnlow density mantle material (anomalous mantle) that intrudesrnitself into the lower crust