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In magma‐rich rifts, normal faulting is commonly thought to be induced by dike intrusions. However, whether fault slip occurs purely tectonically is unclear. An earthquake sequence starting with a Mw 5.5 earthquake occurred in December 2022 in northern Afar, a continental rift near breakup. InSAR measurements show that seismicity was caused by normal faulting alone, without involvement of magma movements. Our best‐fit InSAR models show that conjugate faults ruptured during the seismic sequence with mainly normal dip‐slip and total deformation corresponding to a Mw 5.7 event, in agreement with local seismic recordings. Our models show that tectonic faulting accommodates 26 cm of extension corresponding to ∼30 years of plate spreading without any link to magma. Our observations point toward significant along‐rift variation in the proportion of extension from faulting, potentially caused by along‐rift variations in rate of extension and/or from a spatially and temporally segmented supply of magma. Plain Language Summary The Earth's continents move away from each other forming a rift valley between the two separating tectonic plates. In mature stages of the continental rupture process, it is commonly accepted that plate separation occurs from the migration of molten rock (magma) toward the Earth's surface in narrow zones beneath the rift valley. Brittle faulting of the plate was thought to be less important. In this study we analyze the recent earthquake sequence of 26–28 December 2022 in the volcanically active northern Afar rift of Ethiopia. We show that, while the sequence occurred within the rift valley, it was caused by pure faulting without any involvement of magma migrations. These observations are unexpected and show that faults alone can assist plate separation even in mature and magma‐rich rift valleys. Key Points A seismic sequence with a Mw 5.5 mainshock occurred in the Bada region of northern Afar rift between 26 and 28 December 2022 InSAR models and seismicity revealed co‐seismic deformation along conjugate faults with no involvement of magma motions Our observations show that extension can be achieved through purely tectonic processes in magma‐rich continental rifts

Central Afar is shaped by the interaction between the Red Sea (RS) and Gulf of Aden (GoA) rifts. While there have been several studies conducted in the region, we know surprisingly little about the mechanism of connection between these two rift branches. Here we use high‐resolution 3D lithospheric scale geodynamic modeling to capture the evolution of linkage between the RS and GoA rifts in central Afar. Our results demonstrate that the two rifts initially overlap and interact across a broad zone of faulting and vertical axis block rotation. However, through time, rift overlap is abandoned in favor of direct linkage which generates a series of localized en‐echelon basins. The present‐day direct linkage between the two rifts is supported by geodetic observations. Our study reconciles previously proposed models for the RS and GoA rift connection by considering spatial and temporal evolution of the rifts. Plain Language Summary Rifts are places where tectonic plates move away from each other. They normally start as short, isolated features, and then grow and connect together to eventually form oceans. Central Afar in East Africa is a great location to study how these rifts form and grow by connecting with other rifts. In this area, the Red Sea (RS) and Gulf of Aden (GoA) rifts interact, but it is not clear how this happened through time. Some studies suggest that the two rifts form an overlap zone where blocks within the overlap rotate, while others argue that the two rifts directly link and form a continuous rift zone. To resolve this debate, we conducted a high‐resolution computer simulation of the evolution of the RS and GoA rifts in central Afar. We compared our model results with earthquake positions and satellite data that constrain the present‐day motion of the plates. Our results demonstrate that the RS and GoA rifts first overlapped for a few millions of years, and then formed a direct linkage. Our study suggests that both conceptual models can be reconciled when we consider the temporal evolution of the two rifts through geological times. Key Points Analyzing the spatiotemporal evolution of rifts can address the controversial issue on the connection between propagating rifts We present results from InSAR and geodynamic models to describe the connection between Red Sea (RS) and Gulf of Aden (GoA) rifts in central Afar The connection between the two rifts evolves from rift overlap to direct linkage elucidating the observed deformation in the region

This study investigates the structurally-controlled fluid flow of the Lake Abhe Geothermal Field (LAGF), using multiscale structural lineament distribution mapping and field observations. The LAGF lies within the Gob Aad graben in the Afar depression, at the junction of three rifts, along the Djibouti-Ethiopia border. Numerous hydrothermal surface manifestations on the lake’s eastern shore, including steam vents, hot springs and carbonate chimney structures, reflect the geothermal activity of this area. Structural features of the LAGF area are dominated by ESE-extensional faults that form a series of narrow elongated horst, graben and half-graben structures. Fault interaction and accommodation zones, such as fault intersections and relay ramps, as well as possible breaching faults are also identified in the area. The control of the main ESE-structural direction over the distribution of hydrothermal chimneys and hot springs indicates these faults to be the primary permeability fluid pathways of the LAGF. Signs of enhanced hydrothermal activity at fault intersections further suggest that structural intersections locally increase fracture-related permeability. Field observations combined with satellite image analysis also reveal a lateral migration of the hydrothermal outflows over a short period of time (during the past several thousands to tens of thousands of years) from the SE to the NW. Finally, this study discusses the potential role of N-striking faults, which may either act as vertical drains channeling fluids from south to north or as barriers preventing eastward fluid migration. Overall, this study provides new insights into the tectonically driven fluid flow dynamics of the LAGF, which may support further exploration of this remarkable site and promote its geothermal development. Le lac Abhé est situé dans le graben de Gob Aad, au sein de la dépression de 1’Afar, au niveau de la frontière entre la République de Djibouti et l’Éthiopie. Les nombreuses manifestations hydrothermales de surface présentes sur la rive orientale du lac, notamment les évents de vapeur, les sources chaudes et les cheminées carbonatées, reflètent l’activité géothermique de cette région. Cette étude décrit les circulations de fluides hydrothermaux du champ géothermique du lac Abhé (LAGF), contrôlé par la structuration tectonique de la zone, en s’appuyant sur une cartographie multi-échelle de la distribution des linéaments structuraux et des observations de terrain. Les caractéristiques structurales de la zone du LAGF sont dominées par des failles extensives orientées ESE, qui forment une série de blocs structuraux de type horst, graben et demi-graben. Le contrôle exercé par cette orientation structurale dominante sur la distribution des cheminées hydrothermales et des sources chaudes indique que ces failles constituent le principal chemin de circulation de fluides du LAGF. Des zones d’interaction de failles, telles que des intersections de failles et des rampes de relais ont également été identifiées dans la région. Ces structures représentent des chemins supplémentaires de percolation de fluides, améliorant ainsi la connectivité globale du réseau de failles du LAGF. Les observations de terrain, combinées à l’analyse d’images satellitaires, révèlent également une migration des circulations hydrothermales au fil du temps, migrant du sud-est vers le nord-ouest de la zone d’étude. De plus, cette étude discute du rôle potentiel que peuvent jouer les structures orientées N-S de cette zone, soit de drain canalisant les écoulements de fluides du sud vers le nord, soit de barrière limitant leur migration vers l’est. Ainsi, cette étude offre de nouvelles perspectives sur les circulations des fluides du LAGF, largement influencées par la tectonique. Ces résultats peuvent guider de futures explorations de ce site remarquable et favoriser son développement géothermique.

Magmatism plays a key role in accommodating and localizing extension during continental breakup. However, how the crustal magmatic systems evolve at the continental-ocean transition is poorly understood. We address these questions by studying the evolution of the magmatic system in the rift of Central Afar (Ethiopia), currently marking the transition from continental rifting to oceanic spreading. We focus on the voluminous and widespread Upper Stratoid Series (2.6–1.1 Ma) and the following Central Afar Gulf Series (1.1–0.6 Ma), the latter corresponding to localization of volcanism in narrow magmatic segments. We carried out the first systematic study of major and trace element mineral chemistry for these two Series and integrated it with geothermobarometry estimates and geochemical modeling, to reconstruct the evolution of the magmatic system architecture during rift localization. The Upper Stratoid magmas evolved by fractional crystallization in a melt-rich, moderately zoned, middle-lower crustal (10–18 km) magmatic system, from where they rose directly to the surface. Polybaric plagioclase convection and dissolution of a plagioclase-rich crystal mush is recorded in the phenocryst texture and chemistry. The Central Afar Gulf magmas evolved at similar depth in a more complex and dynamic storage system, with magma rising and mixing through multiple, relatively small, crystal-rich and interconnected reservoirs. Our study documents the transition during the continental breakup, from an overall stable and melt-rich magmatic system feeding the voluminous and homogeneous Upper Stratoid eruptions to a more dynamic, interconnected and crystal-rich situation feeding small-volume eruption while the rift localizes.

New helium isotope data for basalt glasses from the Gulf of Tadjoura and Gulf of Aden reveal a mantle plume signal that has 3He/4He up to 17 RA. In the Gulf of Aden, plume helium is detectable ∼380 km from the Afar triple junction, up to the Shukra El Sheik Fracture Zone along the West Sheba Ridge, but not beyond. The trace of the fracture zone onto the coastal margins also marks the eastward extent of volcanic terranes attributed to Afar plume influence on the ocean‐continent transition. The lack of elevated 3He/4He beyond this point and the history of westward propagation of spreading in the Gulf of Aden toward the triple junction indicate that the Afar plume has a limited influence on modern‐day crustal accretion along most of the Sheba Ridge. Eastward of the Afar plume influence, basalts show uniform 3He/4He = 8.08 ± 0.20 RA (1σ, n = 22) along >1,100 km of the ridge axis. This is among the most uniform sections of the global mid‐ocean ridge system for helium isotopes. The uniformity likely results from enhanced homogenization by small‐scale convection in the upper mantle beneath ultra‐slow spreading ridges. Regional He–Pb–Nd–Sr isotope variations follow a pattern similar to that for ocean island basalts, showing a decrease in 3He/4He as the proportion of recycled material increases in the mantle source region. Source contributions include the Afar mantle plume, shallow asthenosphere, Pan‐African lithosphere, and a sporadic HIMU component that originates either from the continental lithosphere or from within the Afar plume.

The Dallol volcano on the axis of the Erta Ale ridge (Afar rift) offers an ideal opportunity to study the interaction between magmatic and hydrothermal processes. Volcanic activity in Dallol has developed in an area below sea level with a salt plain. Dallol has been actively deforming since InSAR measurements started in the area in 2004. However, the source of deformation under Dallol remains unclear. We present a new InSAR study of Dallol from 2014 to 2023 showing at least three concentric deformation signals of range increase consistent with subsidence with rates ranging 23–43 mm/yr in the satellite Line‐of‐Sight. The main subsidence occurs at Dallol volcano, and two smaller maxima occur at the Black Mountain and the Bubbling Pool areas to the south and southwest of Dallol, respectively. Our modeling indicates that the deformation is caused by contraction of three sill‐shaped sources (Okada tensile dislocations) at depths ranging 0.6–1.5 km, each with a volume contraction in the range 1.8–5.5 × 104 m3/yr. Time series analysis shows that the subsidence at Dallol volcano and Black Mountain was continuous and linear in time. Furthermore, an integrated observation of InSAR with the geology, resistivity image and seismic reflection of the area suggest that the 1.5 km deep source under Dallol is the cooling and contraction of a magma reservoir. At Black Mountain (1 km deep) and Bubbling Pool (0.6 km deep), the data suggest that subsidence is due to either a pressure decreases in the shallow hydrothermal system and/or salt dissolution. Plain Language Summary Ground motions are common in geologically active regions, such as the East African rift. This can be due to faults, molten rock (magma), or heated water (hydrothermal fluids) moving beneath the Earth's surface and causing it to move. In this study, we investigate the causes of ground motion at Dallol volcano and its surroundings, a spectacular area in the northern Afar rift with distinctive geological and environmental features. In this study, we used a satellite measurement technique called InSAR to map ground motion at Dallol from 2014 to 2023 with sub‐cm accuracy. Our study revealed the three areas where the ground is constantly lowering at rates of up to nearly 5 cm per year. These areas are Dallol volcano, Bubbling Pool and Black Mountain. To find out what process below the ground causes the surface to move, we created model simulations of our satellite observations and found that three sheet‐shaped areas of decompression exist under Dallol. These simulations combined with other observations of the subsurface suggest that the sources of decompression are diverse: due to magma cooling and contracting, pressure drops in the hydrothermal steam zone, and areas where the subsurface salt is dissolving. Key Points InSAR study of deformation in the magmatically and geothermally active area of Dallol, Danakil, East African rift InSAR time series and velocity maps show three subsiding deformation signals on the Dallol volcano and its surroundings InSAR modeling indicates that the subsidence signals are related to active magmatism, hydrothermal and salt dissolution processes

The relationship between rifting and continental flood basalt eruptions is debated, and a control by mantle plume is commonly invoked for flood basalts production. In this work, we investigate the relationship between magmatism and rifting by studying the flood basalts erupted in Afar (4.5–0.6 Ma), known as the Stratoid and Gulf Series. We present new field observations and petrography, major and trace elements analyses and mineral chemistry of lavas collected during a regional campaign in Afar. The Series are characterized by E‐MORB magmatism and residual amphibole in the mantle source, consistent with the contribution of metasomatized sub‐continental lithospheric mantle during partial melting. Differences in garnet‐compatible elements indicate a shallower melting column for the oldest and youngest products (4.5–2.6 Ma Lower Stratoid Series; 1.1–0.6 Ma Gulf Series), and deeper for the products erupted at 2.6–1.1 Ma (Upper Stratoid Series). Incompatible element ratios (Th/Nb, Th/Zr) indicate a higher degree of partial melting for the Gulf with respect to the Upper Stratoid Series. Accordingly with independent geophysical and stratigraphic evidence, we explain our results with rift re‐localization: the Pliocene rift caused thinning of the lithosphere and the Lower Stratoid eruptions in Southern Afar, then the Pleistocene rift jumped to Central Afar under a less‐extended lithosphere, producing the Upper Stratoid and, subsequently, as stretching of the lithosphere localized, the Gulf Series formed. Our findings suggest that rift migration and localization can exert a fundamental control on the spatial variability and character of flood basalts without requiring variations on the activity of the mantle plume. Plain Language Summary Afar is a volcanically active low‐lying area in Ethiopia, where the separation of the tectonic plates is breaking up the African continent and leading to the formation of new oceans (i.e., Red Sea, Gulf of Aden). It is therefore an excellent place to study the role of volcanism and related subsurface movements of magma during this transition from continent to ocean. In this work, we studied the Stratoid Series, a huge succession of basaltic lava flows covering much of the Afar depression, and the younger Afar Gulf Series lava flows, which were jointly erupted from 4.5 to 0.6 Ma. This study allows us to identify different mantle sources producing the magmas erupted during the breaking‐up process and to recognize two distinct episodes of “break‐up” in Afar. We interpret the process that guides the passage from one to the other and identify the “evolutionary stages” of the break‐up process toward what is going to be a new ocean. Key Points Metasomatized, amphibole‐bearing lithospheric component in the mantle sources of the 4.5–0.6 Ma basaltic magmatism in Afar Deeper partial melting column for the Upper Stratoid Series mantle source with respect to the Lower Stratoid and the Gulf Series Stratoid Series flood basalt volcanism related to rift jump of the Red Sea rift branch and not to a single magmatic event

In recent years, an increasing number of distribution maps of invasive alien plant species (IAPS) have been published using different machine learning algorithms (MLAs). However, for designing spatially explicit management strategies, distribution maps should include information on the local cover/abundance of the IAPS. This study compares the performances of five MLAs: gradient boosting machine in two different implementations, random forest, support vector machine and deep learning neural network, one ensemble model and a generalized linear model; thereby identifying the best‐performing ones in mapping the fractional cover/abundance and distribution of IPAS, in this case called Prosopis juliflora (SW. DC.). Field level Prosopis cover and spatial datasets of seventeen biophysical and anthropogenic variables were collected, processed, and used to train and validate the algorithms so as to generate fractional cover maps of Prosopis in the dryland ecosystem of the Afar Region, Ethiopia. Out of the seven tested algorithms, random forest performed the best with an accuracy of 92% and sensitivity and specificity >0.89. The next best‐performing algorithms were the ensemble model and gradient boosting machine with an accuracy of 89% and 88%, respectively. The other tested algorithms achieved comparably low performances. The strong explanatory variables for Prosopis distributions in all models were NDVI, elevation, distance to villages and distance to rivers; rainfall, temperature, near‐infrared and red reflectance, whereas topographic variables, except for elevation, did not contribute much to the current distribution of Prosopis. According to the random forest model, a total of 1.173 million ha (12.33% of the study region) was found to be invaded by Prosopis to varying degrees of cover. Our findings demonstrate that MLAs can be successfully used to develop fractional cover maps of plant species, particularly IAPS so as to design targeted and spatially explicit management strategies. After comparing machine learning algorithms (MLAs) for species distribution mapping, we found that the random forest algorithm is the best for species distribution fractional cover mapping. Our findings demonstrate that MLAs can be successfully used to develop fractional cover maps of plant species in view of a targeted, spatially explicit management.

We provide a new set of complementary geodetic data for the 2005 rifting event of Afar (Ethiopia). Interferometric synthetic aperture radar and subpixel correlations of synthetic aperture radar and SPOT images allow us to deduce 3‐D surface displacement unambiguously. We determine the geometry of the dike and neighboring magma chambers and invert for the distribution of opening of the dike, as well as slip on rift border faults. The volume of the 2005 dike (1.5–2.0 km3) is not balanced by sufficient volume loss at Dabbahu and Gabho volcanoes (0.42 and 0.12 km3, respectively). Taking into account the deflation of a suspected deep midsegment magma chamber simultaneously to dike intrusion produces a smoother opening distribution along the southern segment. Above the dike, faults slipped by an average 3 m, yielding an estimated geodetic moment of 3.5 × 1019 Nm, one order of magnitude larger than the cumulative seismic moment released during the earthquake swarm. Between Dabbahu and Ado'Ale volcanic complexes, significant opening occurred on the western side of the dike. The anomalous location of the dike at this latitude, offset to the east of the axial depression, may explain this phenomenon. A two‐stage intrusion scenario is proposed, whereby rifting in the northern Manda Hararo Rift was triggered by magma upwelling in the Dabbahu area, at the northern extremity of the magmatic segment. Although vigorous dike injection occurred during the September 2005 event, the tectonic stress deficit since the previous rifting episode was not fully released, leading to further intrusions in 2006–2009.

Afar is undergoing the final stages of continental rifting and hosts the triple junction between the Red Sea, Gulf of Aden, and Main Ethiopian rifts. To better understand the nature of the crust and continental breakup in the region, we calculate teleseismic receiver functions across northeastern Afar and the Danakil microplate, using new data from a regional deployment in Eritrea. We estimate the Moho depth and bulk crustal VP/VS ratio using the H‐κ stacking method. The heterogeneity of our crustal thickness estimates (∼19–35 km) indicates that the Danakil microplate has undergone stretching and crustal thinning. By investigating the relationship between crustal thickness and topographic elevation, we estimate the regional crustal bulk density as ρc ≈ 2,850 ± 20 kg m−3, which is higher than expected, given the crustal thickness of the region. We show that topography is 1.5 ± 0.4 km higher than would be expected due to crustal isostasy alone. We propose that this topography is supported by the same hot mantle upwelling suggested to be responsible for the onset of rifting in East Africa. Uplift is generated due to the presence of a hot thermal anomaly beneath the plate and by thinning of the lithospheric mantle. Our results are consistent with a number of independent constraints on the thermal structure of the asthenospheric and lithospheric mantle. Evidence of melt within the crust is provided by anomalously high VP/VS ratios of >1.9, demonstrating that magma‐assisted extension continues to be important in the final stages of continental breakup. Plain Language Summary Afar is an area of northern Ethiopia that extends into Eritrea. It hosts three tectonic plate boundaries that are pulling apart from one another (rifting) as continental breakup is occurring. These rifting processes have led to a complicated tectonic history; isolating a small microcontinent (the Danakil) and giving rise to volcanism across the region. To better understand the nature of the crust, we study seismic data to estimate the crustal thickness and the ratio of seismic wave speeds. Our results indicate that the crust shows substantial variation in thickness, meaning that the Danakil microplate has undergone crustal thinning. We use our results to determine that dynamic mantle processes are responsible for supporting the elevation of the region. We also show that partially molten rock (magma) is likely to be present in the crust beneath northeastern Afar and the Danakil microplate, which is evidence that magma assists with continental breakup. Key Points Receiver functions produce the first estimates of Eritrean bulk crustal properties The crust of Afar and the Danakil microplate is denser than global average and highly heterogeneous Evidence found for melt within crust and for support from hotter mantle propping up topography beneath Afar and the Danakil microplate