The geographical origin of modern humans is the subject of ongoing scientific debate. The 'multiregional evolution' hypothesis argues that modern humans evolved semi-independently in Europe, Asia and Africa between 100,000 and 40,000 years ago, whereas the 'out of Africa' hypothesis contends that modern humans evolved in Africa between 200 and 100 kyr ago, migrating to Eurasia at some later time. Direct palaeontological, archaeological and biological evidence is necessary to resolve this debate. Here we report the discovery of early Middle Stone Age artefacts in an emerged reef terrace on the Red Sea coast of Eritrea, which we date to the last interglacial (about 125 kyr ago) using U-Th mass spectrometry techniques on fossil corals. The geological setting of these artefacts shows that early humans occupied coastal areas and exploited near-shore marine food resources in East Africa by this time. Together with similar, tentatively dated discoveries from South Africa this is the earliest well-dated evidence for human adaptation to a coastal marine environment, heralding an expansion in the range and complexity of human behaviour from one end of Africa to the other. This new, wide-spread adaptive strategy may, in part, signal the onset of modern human behaviour, which supports an African origin for modern humans by 125 kyr ago.

The presence of ophiolite complexes in NE and E Africa has been documented using Landsat, field and geochemical studies. The present work identifies five major ophiolitic sutures in NE Africa, while plate reconstruction of Africa and Madagascar suggests a possible sixth ophiolite belt to the east. The ophiolites are considered to be remnants of supra-subduction zones and back-arc basins. The ophiolites are dismembered, and their mode of occurrence varies widely resulting in different structural relationships. In Western Ethiopia, the Yubdo complex is formed of harzburgite which grades into a cumulate sequence of ultramafic and gabbroic rocks and metabasalts. In Kenya, the Baragoi complex is formed of tectonized harzburgite with dunite and chromite pods, a cumulate sequence of ultramafic and gabbroic units and a dyke unit. Trace element data from the Baragoi complex show a transitional mid-ocean ridge basaltic to island arc tholeiitic affinity, and the presence of boninites suggests a supra-subduction setting, while data from the Adola-Moyale belt (S. Ethiopia-NE Kenya) indicate an island-arc and MORB geochemistry, which developed in a back-arc tectonic setting. In Sudan, the Ingessana complex which has an island arc tholeiitic tectonic affinity indicates development in a supra-subduction setting, while the trace element suggest that the Sol Hamed complex developed in a back-arc basin. These ophiolite belts represent sutures marking the position of island arcs extending to those in Saudi Arabia on a pre-Red Sea drift reconstruction and further south to Mozambique. The terrane delimited by a proposed Ingessana-Port Sudan suture and by the Adola-Moyale ophiolite belts as defined in this study encompasses an area in which the crust was derived from oceanic and island arc material. Relative age reconstruction across the Arabian-Nubian Shield in East Africa broadly indicates eastward younging of the ophiolite belts. Regional geological, tectonic and geochemical studies suggest rifting at c. 1200 Ma and subsequent convergence led to the development of intra-oceanic arcs and associated marginal basins in the north and narrow basins within the sialic basement gneisses further south in Kenya and Tanzania. This was followed by continent-continent collision which led to accretion of island arcs by gentle collision from the northeast in Saudi Arabia and severe crustal shortening in S Sudan, Kenya and SE Ethiopia as compared to Saudi Arabia, NE Sudan and N and W Ethiopia owing to oblique collision from the southeast.

We present a synthesis of diverse observations of the first recorded eruption of Nabro volcano, Eritrea, which began on 12 June 2011. While no monitoring of the volcano was in effect at the time, it has been possible to reconstruct the nature and evolution of the eruption through analysis of regional seismological and infrasound data and satellite remote sensing data, supplemented by petrological analysis of erupted products and brief field surveys. The event is notable for the comparative rarity of recorded historical eruptions in the region and of caldera systems in general, for the prodigious quantity of SO2 emitted into the atmosphere and the significant human impacts that ensued notwithstanding the low population density of the Afar region. It is also relevant in understanding the broader magmatic and tectonic significance of the volcanic massif of which Nabro forms a part and which strikes obliquely to the principal rifting directions in the Red Sea and northern Afar. The whole-rock compositions of the erupted lavas and tephra range from trachybasaltic to trachybasaltic andesite, and crystal-hosted melt inclusions contain up to 3,000 ppm of sulphur by weight. The eruption was preceded by significant seismicity, detected by regional networks of sensors and accompanied by sustained tremor. Substantial infrasound was recorded at distances of hundreds to thousands of kilometres from the vent, beginning at the onset of the eruption and continuing for weeks. Analysis of ground deformation suggests the eruption was fed by a shallow, NW–SE-trending dike, which is consistent with field and satellite observations of vent distributions. Despite lack of prior planning and preparedness for volcanic events in the country, rapid coordination of the emergency response mitigated the human costs of the eruption.

Abstrad: New K-Ar dates are presented for areas in W and SE Ethiopia. In the west, the dates distinguish the Geba Basalts of 40 to 32 Ma (previously determined by Merla et al. 1979) from the Welega Shield Volcanics which are shown to range from 11.2 f 2.2 to 7.8 f 1.6 Ma. In SE Ethiopia, the Lower Stratoid flood basalts range from 30 f 4.5 to 23.5 f 4.5 Ma and are unconformably overlain by the Reira-Sanete shield volcanics which range from c. 15 to c. 2 Ma. The unconformity is marked by a palaeosol as are several of the intervals between the major volcanic stages of Ethiopia.Using new field observations, together with previously published results and unpublished data from the Ethiopian Institute of Geological Surveys, it is suggested that the Ethiopian Flood Basalts were erupted in three major stages. Stage 1, which is mainly older than 40 Ma is separated from Stage 2, 34 to 30 Ma for NW Ethiopia and 40 to 30 Ma for SW Ethiopia, by erosional unconformities. Stage 3 spans 30 to 26 Ma in NW Ethiopia, and 30 to 21 Ma in SW Ethiopia and both are marked by the incoming of silicic volcanism. In W Ethiopia, Stages 1 and 3 are not developed, whilst in SE Ethiopia the Tertiary volcanism commences with Stage 3 flood basalts. The overlying shield volcanics; (25 to 13 Ma in NW Ethiopia and 15 to 7 Ma in W Ethiopia) represent a localized terminal episode built on the Plateau and are considered a fourth stage.

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