Large volcanic landslide and debris avalanche deposit at Meru, Tanzania
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Meru volcano is located within the Northern Tanzanian Divergence Zone where the east branch of the East African Rift splits into several branches. The 4565-m-high Meru volcano is breached on the east flank by a horseshoe-shaped scar following a major collapse associated with the Momella debris avalanche approximately 9000 years ago. Remote sensing combined with detailed field mapping allowed the characterisation of the Momella debris avalanche deposit, structure, and texture. Hummocks, ridges, lineaments, lobes, grabens and shear zones are observed on the surface of the deposit. The most common facies observed are the mixed facies with indurated and shattered outcrops and the matrix facies. The collapse involved a volume of 20 ± 2 km3 with a deposit that spread over an area of 1250 km2, up to the base of Kilimanjaro. Based on field evidence, we suggest that water played a key role in the deformation, facies formation, avalanche emplacement and mobility of the entire deposit but to a lesser extent south of Ngurodoto complex. The deformation and emplacement of the avalanche were accommodated by both extension and shearing on a water-fluidised basal layer.
KeywordsMeru Tanzania Volcanic landslide Debris avalanche deposit Water
The project has been supported by a post doc fellowship to AD funded by the Fonds Wetenschappelijk Onderzoek (FWO-Vlaanderen). We thank P. Lahitte, K. Fontijn, C. Shemsanga and M. A. Del Marmol for discussion. E. De Pelsmaeke is thanked for access to microscope. The aerial pictures have been purchased at the Division Mapping in Dar Es Salaam. Authorisations to work in Tanzania and Meru National Park have been provided by COSTECH, TAWIRI and TANAPA. AD is greatly thankful to Mr. and Ms. Patel for unlimited and welcome access to Arusha Aggregates quarry, to the rangers of Meru National Park, especially Magoiga and our cooks and porters, specifically Mikael, and of course, Moses and Alois for all their precious help and friendship. The manuscript has benefited from constructive comments from Marc Andre Brideau (Editor), J. Procter and an anonymous reviewer.
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