Wednesday, 22 July 2020

The East African Rift System and Landslides

The East African Rift System and Landslides

When I think of the East African Rift System, landslides are not the first thing on my mind. THIS ARTICLE from one of my most prolific sources, Earth-logs, may make me change my mind. 

The "Rise to the Rift" was much mentioned many years ago. We now know what causes it - bulging of the continental crust resulting both from its unloading by thinning along the rifts and the buoyancy conferred by high heat flow in the mantle beneath - but the result is landslides.

The East African Rift System (Credit: P.C. Neupane, M.Sc thesis 2011; Fig. 1)

There is enhanced erosion, both into the rift and outwards, especially onto the the Indian Ocean continental shelf. Recent oil exploration work, offshore Tanzania, has illuminated this.

In particular it has shown the presence of a vast submarine landslide, called (intriguingly) the Mafia mega-slide. It is thought that it was caused by a large earthquake and would have caused a large tsunami.

Seismic reflection profile parallel to the Tanzanian coastline with the Mafia mega-slide highlighted in green (Credit: Maselli et al. 2020; Fig. 5)

You can find details of this work HERE. The main thrust of the paper is using the records of offshore sedimentation to fix the dates of the rifting and to note the dangers of future submarine landslides.

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