Dramatic and rapid changes from volcanic activity in Ethiopia appear to have set the stage for the emergence of Homo sapiens around 200,000 years ago. The first known fossil evidence for our species was unearthed there, where explosive volcanic activity was dramatically changing the landscape and environment, according to new research published in the journal Nature Communications.
"Pyroclastic flows -- hot currents of gas, ash and rock -- would have inundated large tracts of the rift floor while ash and pumice fallout from larger plumes are likely to have covered regions to at least 100 kilometers (62 miles) from the vent," lead author William Hutchison of the University of Oxford's Department of Earth Sciences told Seeker.
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While all of this was going on, the earliest-known members of our species were not very far away. The fossils from the Omo Kibish rock formation of southern Ethiopia date to 195,000 years ago. These early humans likely viewed the eruptions from a safe enough distance -- but their presence in the region as the volcanic activity took place seems to be too coincidental to ignore.
Hutchison said that the volcano eruptions occurred along the East African Rift System, which is a still-active continental rift where Africa is slowly being pulled apart. One segment runs through Ethiopia, where a population of around 10 million people live alongside it.
As the continent gradually pulls apart, Earth's crust along the rift is extended and thinned, allowing molten rock (magma) to rise.
Hutchison and his team reconstructed the eruptive history of a 124-mile-long segment of the rift in Ethiopia by studying the Aluto and Corbetti volcanoes there. The researchers used two techniques, argon isotopes and radiocarbon analysis, to determine the dates of erupted rocks. They also analyzed the sizes of eruptions along the rift over time.
"We suggest that an increased flux of melt from the mantle into the crust generated the large magma chambers that over-pressured and erupted 320,000–170,000 years ago," Hutchison said. "These events are called flare-ups and have been identified before in other rift zones such as the Taupo Volcanic Zone in New Zealand."