Risk and reward: Explosive eruptions and obsidian lithic resource at Nabro volcano (Eritrea)

Abstract

Compared with other manifestations of climate variability that may not be perceived within a human lifetime, abrupt environmental disturbances arising from volcanism can be directly experienced. Despite abundant Pleistocene calderas in the East African Rift and Afar, and the significance of regional tephra horizons for archaeological and paleoenvironmental dating, the entanglements of volcanoes and their eruptions with human behaviour and paleoecology have received little attention. Here, we focus on the intertwined human and eruptive history at Nabro, a caldera-topped volcanic massif close to the Red Sea littoral of Eritrea. Nabro exemplifies the antagonism of Risk and reward at Nabro P a g e | 2 opportunities and threats posed by a large silicic volcano, active at least since the Middle Pleistocene and as recently as 2011. Using argon isotopic measurements, we establish the first chronology of key eruptive stages of Nabro and neighbouring Mallahle revealing a history of explosive and effusive volcanism in the Middle and Late Pleistocene. Past eruptions were an important source of obsidian that was exchanged over long distances across land and sea during the Neolithic. We infer that the availability of high-quality obsidian, combined with Nabro's favourable microclimate and proximity to the Red Sea coast, likely attracted humans to this volcanic landmark since the later Middle Pleistocene. Drawing on observations of the immediate impact of the 2011 eruption on landscape and local pastoralist communities, we consider the impacts of past volcanic cataclysms on human populations. In addition to the threat to life, explosive eruptions of Nabro circa 130 ka and 62 ka ago would have abruptly curtailed procurement of its obsidian resource. Our findings suggest further attention be paid to evaluating the significance of East African volcanic landscapes, eruptions and resources for understanding human behaviour in deep antiquity.

Integrative geochronology calibrates the Middle and Late Stone Ages of Ethiopia’s Afar Rift

“…Indeed, from eastern to western Africa, understanding the nature of the relationship between the MSA and LSA remains incomplete, with little consensus on issues ranging from timing to geography to technology. Understanding the temporal and spatial variation in technologies (51)(52)(53), subsistence (54), mobility (55,56), and potential ecosystem modifications (57) of Middle and Late Pleistocene human populations is best accomplished via comprehensive research on stratified, calibrated sequences of timesuccessive, geographically limited archaeological occurrences associated with skeletal remains. The rapidly expanding nexus of MSA localities in the Afar thereby creates additional opportunities for progress in testing the modes and tempos of biological and cultural change and the causes of observed variation (58)(59)(60)(61).…”

9000 years of human lakeside adaptation in the Ethiopian Afar: Fisher-foragers and the first pastoralists in the Lake Abhe basin during the African Humid Period

“…It has been argued that mobility associated with herding may have supported its spread, both through interaction and exchange of livestock with foragers, and through social networks that enabled them to thrive faced with growing aridity (Marshall et al 2011). It has also been suggested that maritime mobility across the Red Sea, confirmed through obsidian sourcing studies , Oppenheimer et al 2019) may have played a role in the spread of herding by means of coastal fisher-herding communities from southern Arabia (Gutherz et al 2017;. However, the current study provides new data that suggest traditions in the Abhe Lake basin had few to no parallels with those in surrounding regions across the three periods of settlement documented in the region.…”

Evidence of active magmatic rifting at the Ma’Alalta volcanic field (Afar, Ethiopia)

“…1a). These are large stratovolcanoes that produced caldera-forming explosive eruptions (Barberi et al 1974a;Wiart and Oppenheimer 2005;Oppenheimer et al 2019) and lava flows generally more alkaline with respect to the tholeiitic-transitional axial volcanism (Civetta et al 1975;De Fino et al 1978;Donovan et al 2018). The most recent eruption of a marginal volcano was in 2011 at Nabro, which produced basaltic to basaltic trachyandesite tephra and lava (Hamlyn et al 2018;Donovan et al 2018).…”