Monte Muambe is volcanic caldera located south-east of Moatize in Tete Province of Mozambique Morphologically, Monte Muambe is ring-shaped feature, composed of Karroo sandstones which rise from peneplain plateau at altitude between 250 m in the south and 300 m in the north. The rim of the caldera forms well-developed circular ridge of altered and indurated Karroo sandstones (gritstones) rising approximately 500 m above the plain of unaltered Karroo sediments. Due to hardness of altered Karroo sediments, after continuous, long-time erosion, Monte Muambe at present is well-developed circular ridge (caldera), basin-shaped, steep-sided and crater-like depression inside. The core of the circular structure is 200 m lower from its periphery. Geology of adjacent area The region of Monte Muambe is situated on southern margin of the Tete gabbro-diorite complex of Precambrian ages, in a depression filled in Mesozoik by sediments and volcanic activity products of the Karroo System. Karroo System Karroo sediments are in tectonic relationship with older rocks. The boundary of the Tete gabbro-diorite complex is E -W striking dislocation. These sediments form an east-west trending belt, gently dipping to southeast in the sedimentary formation and volcanic rocks of Monte Muambe area. The succession normally progress from north to the south. From the oldest formations in the north as represented by Serie Tilitos ad Serie Produtiva with coal seams (Beaufort), sedimentation progressed continuously to fossiliferous sandstones, often cross-bedded, including clay-marly beds (Stromberg) - which closed the Karroo sedimentation. Volcanic formation of Stromberg Series consists of amygdaloid basalts plates in the form of lava flows over Karroo sandstones, and dolerite in the form of dykes. Post-Karroo deposits are commonly represented by sandstones and conglomerates with interstratified Mesozoic or younger volcanic rocks. In the Monte Muambe region they are recognized as rocks of Lupata Series. This geologic formation is divided into Lower Lupata Sandstones and Upper Lupata Series. Older sandstones consider to include also rhyolite and younger include alkaline rocks. Only the Upper Lupata Sandstones are developed in Monte Muambe region. The formation consists of two members: clastic, mostly feldspathic various grained sandstones, and volcano erupted - alkali lavas. The intrusive members are syenite and carbonatite. The complete sedimentary sequence is separated in Lupata region, about 10 km southeast of Monte Muambe, in Chincongolo area, near to Lupata Gorge, and consists of Upper Lupata Sandstones formation, intrusive rocks (syenite), carbonatites (intrusive and effusive products) and alkaline extrusive rocks. According to field findings