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Nature and impacts of Middle Pleistocene volcanism in the Ethiopian Rift

Nature and impacts of Middle Pleistocene volcanism in the Ethiopian Rift

The East African Rift has been the focus of decades of research into human origins. Numerous hypotheses have been proposed to link characteristics of the Rift environment and climatic change to hominin speciation events. While these hypotheses have stimulated considerable efforts to obtain palaeoclimatic evidence, comparatively little attention has been paid to the role that geological processes (i.e., tectonics and volcanism) have played in shaping Rift habitability.

Perched between the lake basins of East Africa are sizeable volcanic complexes. Several of these volcanoes underwent very large explosive eruptions in the Quaternary; these events ejected hundreds of cubic kilometres of magma and left behind collapsed calderas and extensive volcanic deposits stacked up on the Rift floor.

Although volcanic ash layers (or tephra) have provided vital age constraints for hominin fossils in paleoanthropological contexts, very few studies have considered the impact these large eruptions had on hominins living in and around the Rift. It is clear that volcanoes attracted hominin populations for their resources (such as obsidian for stone tools), but could major eruptions also have had significant demographic impacts? Could they have triggered migrations along the Rift corridor, or stimulated cultural adaptations? The thrust of this project is to put volcanism centre-stage in the question of Rift palaeoenvironments, and to gather evidence that will help evaluate the implications of large eruptions and associated environmental change for understanding the human trajectory.

This project focuses on the Middle Pleistocene of Ethiopia. Geological evidence indicates that around 300,000- 200,000 years ago a cluster of large eruptions, with individual magnitudes 10-100 times greater than the 1980 Mt. St Helens eruption, occurred in the Ethiopian Rift. This represents a critical time period in the speciation of our own genus, since the earliest anatomically-modern human fossils are found in same region and date to around 200,000 years ago. We are applying a combination of field-based geological observations and laboratory analysis of rock samples to quantify the size and age of major eruptions. We will then apply computational modelling to simulate the range of possible ecosystem impacts these eruptions had, and the implications for contemporary human populations.

Header image: Fantale volcano in the Ethiopian Rift Valley.