Main Ethiopian Rift Research Articles

Eruption style and dynamics of the ~ 87 ka Baricha peralkaline rhyolite eruption in Ethiopia

AbstractPeralkaline rhyolites are a rare magma type, typically associated with continental rift settings, and characterised by excess alkalis relative to alumina and a moderate-low viscosity compared to calc-alkaline equivalents. Despite their prevalence in extensional rift settings, such as the Main Ethiopian Rift, eruption dynamics of peralkaline magmas are poorly understood and have never been directly observed. To address the knowledge gap, this study investigates the style and dynamics of the ~ 87 ka explosive eruption at Baricha volcano as a case study. This eruption deposited widespread pumice lapilli fall and pyroclastic density currents, which provide valuable information on pre- and syn-eruptive magmatic processes. By examining the physical and textural features of the eruption products at different stratigraphic levels, we reconstruct eruption dynamics over time. Our analysis reveals that the eruption had three distinct phases, each characterised by different types of tephra fall deposits and associated with different plume and vent conditions. Specifically, deposits of phases 1 and 3 were characterised by massive and well-sorted tephra falls indicative of sustained plume behaviour, while phase 2 deposits were bedded, lithic-rich (i.e. non-juvenile fragments) tephra falls, and pyroclastic density current deposit associated with an unsteady plume and vent-widening phase. The pumice (8–16 mm size fraction) from this eruption is microlite-free, with a bulk density of 400–700 kg m−3 and > 60% total vesicularity. The vesicle size distribution is polymodal, with the most frequent size ranging from 0.001 to 2.4 mm and an estimated vesicle number density of 0.07*107 to 1.6*107 mm−3. The textural observations suggest rapid nucleation occurred during the late phases of magma ascent. Calculated decompression rates of the ascending magma were 0.07–5.6 MPa/s and show a variation between the eruption phases. We conclude that the shift in eruption dynamics alternating between steady to unsteady plume behaviour during the eruption was likely driven by changes in conduit geometry, lithic abundance of the eruptive mixture, decompression rate, and fresh magma injection.

Application of electrical resistivity tomography for groundwater evaluation in Yirgacheffe Town and its environs, Main Ethiopian Rift

Exploring groundwater is crucial in areas with poor surface water quality, such as Yirgacheffe Town and its surroundings. This study aims to assess aquifer materials and groundwater potential using Electrical Resistivity Tomography (ERT) in the region,within the Main Ethiopian Rift. Four electrical resistivity profiles were gathered using a Wenner array with a WDA-1 digital resistivity and induced polarization meter from Chongqing, China. Each profile extended 236 m with 4-m electrode spacing. Data were analyzed and inverted with Res2DinV software and validated against lithological logs. The ERT inversion revealed three subsurface geoelectric layers: (1) massive rhyolite ignimbrite and basalt (>2000 Ωm); (2) weathered rhyolite ignimbrite and basalt (200–2000 Ωm); and (3) topsoil (4–200 Ωm). These results are key for effective water resource management and highlight ERT's utility in similar geological settings.

Phase equilibrium constraints on the pre-eruptive conditions of alkaline basalts of the Main Ethiopian Rift and their bearing on the production of peralkaline rhyolites

Abstract Bimodal magmatism is characteristic of the geodynamic evolution of the Main Ethiopian Rift (MER), which is a reference area for the study of the processes leading to continental break-up before seafloor spreading. There are abundant emissions of basalts and rhyolites, which are in possible parent-daugther relationships. However, the P-T-H2O conditions of production and storage of the basaltic end member remain unclear. Crystallization experiments have been conducted on an alkali basalt from the MER to define its pre-eruptive conditions and shed light on the compositional evolution of derivative liquids and source conditions. The experiments were performed at 100-200 MPa, 975-1080°C, varying H2O/CO2 ratios, corresponding to melt water contents of 1-5 wt%, at fO2 slightly lower than the Fayalite-Magnetite-Quartz (FMQ) solid buffer. Comparison between the petrological attributes of the starting rock and the experiments shows that the basaltic magma was stored at 150-200 MPa, 1050 ± 10°C, with 1-2 wt% H2O in melt, with fO2 near FMQ prior to eruption. Geochemical modelling shows that the corresponding mantle source contained about 0.1 wt% H2O, reflecting a metasomatized source. Extensive crystallization of such basalts produces SiO2-rich liquids, which are not yet peralkaline, however. This underscores that extreme fractionation (>90 wt%) is required in order to produce peralkaline derivatives from mildly alkaline basalts. This extreme fractionation and the water-rich nature of the starting basalt readily explain the H2O-rich condition of peralkaline rhyolites that have fueled caldera forming eruptions in the Rift.

Pulsatory volcanism in the Main Ethiopian Rift and its environmental consequences

The East African Rift is one of Earth’s largest continental landforms. It is recognized as a critical region for understanding hominin evolution yet has also undergone important transformation through ongoing tectonic and volcanic activity. An understanding of the interplay of rift kinematics, magma genesis and geomorphic evolution requires firm geochronology but this has been lacking for much of the East African Rift. Here we present detailed stratigraphic observations and high-precision 40Ar/39Ar ages for major volcanic units in the Central Main Ethiopian Rift. Our new data identify a volumetrically major episode of explosive volcanism between circa 3.85–3.42 million years ago, after aproximately 5-million years-long quiescence. Four other pulses followed but with intensity and magnitude declining over time. We suggest that the observed temporal clustering and the pulsatory volcanic activity may have influenced environmental conditions in the area, with possible implications for hominin evolution.

Physicochemical characteristics and industrial application of Ammacio kaolin in the southwestern central Main Ethiopian Rift

Physicochemical characteristics and industrial application of Ammacio kaolin in the southwestern central Main Ethiopian Rift

Kinematics of rift linkage between the Eastern and Ethiopian rifts in the Turkana Depression, Africa

AbstractRift initiation within cold, thick, strong lithosphere and the evolving linkage to form a contiguous plate boundary remains debated in part owing to the lack of time–space constraints on kinematics of basement‐involved faults. Different rift sectors initiate diachronously and may eventually link to produce a jigsaw spatial pattern, as in the East African rift, and along the Atlantic Ocean margins. The space–time distribution of earthquakes illuminates the geometry and kinematics of fault zones within the crystalline crust, as well as areas with pressurized magma bodies. We use seismicity and Global Navigation System Satellites (GNSS) data from the Turkana Rift Array Investigating Lithospheric Structure (TRAILS) project in East Africa and a new digital compilation of faults and eruptive centres to evaluate models for the kinematic linkage of two initially separate rift sectors: the Main Ethiopian Rift (MER) and the Eastern rift (ER). The ca. 300 km wide zone of linkage includes failed basins and linkage zones; seismicity outlines active structures. Models of GNSS data indicate that the ca. 250 km‐wide zone of seismically active en echelon basins north of the Turkana Depression is a zone, or block, of distributed strain with small counterclockwise rotation that serves to connect the Main Ethiopian and Eastern rifts. Its western boundary is poorly defined owing to data gaps in South Sudan. Strain across the northern and southern boundaries of this block, and an ca. 50 km‐wide kink in the southern Turkana rift is accommodated by en echelon normal faults linked by short strike‐slip faults in crystalline basement, and relay ramps at the surface. Short segments of obliquely oriented basement structures facilitate across‐rift linkage of faults, but basement shear zones and Mesozoic rift faults are not actively straining. This configuration has existed for at least 2–5 My without the development of localized shear zones or transform faults, documenting the importance of distributed deformation in continental rift tectonics.

Magma storage conditions beneath a peralkaline caldera in the Main Ethiopian Rift

The numerous volcanic centres in the Main Ethiopian Rift (MER) present significant but poorly understood hazards to local populations. The MER is also an important site to gain insights into tectonic processes as it captures the transition from continental rifting (to the south) to incipient seafloor spreading (to the north). Peralkaline magmas account for around 90% of the volcanic products found in the MER. Determining the conditions under which these magmas evolve is critical to understanding rift-related volcanism and its associated hazards. Corbetti Caldera has an extensive record of large-scale, predominantly aphyric, peralkaline rhyolite eruptions. However, little is known about the mafic magmas from which these highly differentiated melts have evolved. Here we present data from the only basaltic deposit found within the caldera, coupled with whole rock, glass and mineral analysis of the peralkaline products, to investigate magma storage conditions at Corbetti. We demonstrate that magma mixing played a role in the evolution of the basaltic magmas and use RhyoliteMELTS modelling to show Corbetti's peralkaline magmas likely evolved at pressures between 100 and 250 MPa, from a magma with an initial water content of 0.5–1 wt%, at or below the QFM buffer. Mineral hygrometry on the sparse crystal populations corroborates the RhyoliteMELTS modelling, suggesting that the basaltic magma had 0.1–1.2 ± 0.32 wt% H2O, and the peralkaline magmas an average of ∼5.5 ± 1.25 wt% H2O. These results also match melt inclusion data for Corbetti and other peralkaline systems. We also provide new 40Ar/39Ar ages for two eruptions, a pre-caldera rhyolitic lava flow (206.7 ± 0.9 ka) and a post-caldera peralkaline ignimbrite (160 ± 0.8 ka). These results add to our understanding of the history of Corbetti and the storage conditions of peralkaline magmas within a continental rift setting and highlight the hydrous nature of Corbetti's magmas and the role that H2O plays during explosive eruptions.

Density structures of the upper mantle in the East African Rift System: implications for the evolution of intracontinental rifting

The East African Rift System (EARS) provides an ideal natural laboratory for studying the mechanisms of tectonic plate breakup and continental drift, as well as a unique perspective for exploring the maturation process of continental rifting and its drivers. This study combines high-resolution satellite gravity data and seismic tomography model with an integrated geophysical approach to reveal the density structures in the upper mantle of the EARS. The results show that the northeastern to central Congo and Zimbabwe Craton exhibit significant high-density anomalies extending up to 250 km, which is indicative of a thicker and more intact lithosphere. In contrast, the Uganda, Tanzania, eastern and southern Congo, and Kaapvaal Craton show shallow high-density anomalies underlain by low-density anomalies that are clearly derived from the deeper mantle, indicating a thining of the lithosphere with some degree of possible melting at the base. The various rift segments of the EARS exhibit different rift morphologies. The Main Ethiopian Rift and the Kenya Rift of the Eastern Rift Branch show strong low-density anomalies, indicating intense melting, which is much stronger than that observed in the Western Rift Branch. However, the two rifts may have originated from the same mantle uplift in which the low-density anomalies of the Eastern and Western Rift Branches connected in the deep upper mantle. The lower portion of the Malawi Rift exhibits weaker low-denstiy anomalies, which can be observed to the south of the Malawi Rift, extending further south as a continuation of the EARS. Combining the results of previous kinetics simulations and our density perturbation results, it can be inferred that the Eastern Rift Branch is mainly affected by active rifting, while the Western Rift Branch is affected by both active and passive rifting.

Slope stability modeling using limit equilibrium and finite element methods: A case study of the Adama City, Northern Main Ethiopian Rift

Slope failure is a prominent and recurring geohazard in numerous parts of Ethiopia, including Adama City, which is located in the Northern Main Ethiopian Rift (NMER). The city is surrounded by two ridges oriented in the NNE-SSW direction, which are susceptible to slope instability. Thus, this study is aimed at modeling slope stability along these two ridges using Finite Element Method (FEM) and Limit Equilibrium Method (LEM). The modeling was carried out on slopes of multifaceted geometry composed of eluvium soil, pumice, and moderately to highly-weathered ignimbrites. Critical slope sections were identified using satellite imagery and field manifestations such as slope toe condition and slope face tilting. Their geometries were then inferred from detailed geological cross-sections based on field data. Input parameters for the modeling, such as cohesion, friction angle, and elastic modulus, were calculated via Back Analysis using the Hoek-Brown criterion while unit weight and Poisson ratio were determined from empirical equations. For soil formations, the parameters were determined via standard laboratory experiments. The modeling was then carried out under different conditions, including dry, saturated, static, and dynamic conditions. Results from both LEM and FEM models revealed that three of the four analyzed slope segments were unstable under dynamic and saturated conditions, highlighting the influence and importance of precipitation and seismicity as triggering variables. Results from both methods tend to agree when the critical slip surface passes through a single geological material in both models. However, notable differences arise when the slip surface involves multiple geological materials. Under such conditions, LEM tends to yield higher FOS values compared to FEM. The results also showed that all unstable slopes were associated with the NNE-SSW striking fault of the study area, as inferred from failure surfaces generated from both models and field data. The study concluded that unstable slopes pose a serious risk to nearby residents and infrastructure, and as a remedy, it designed and recommended coupled benching and slope flattening.

Electrical resistivity and magnetic methods in mapping groundwater on the western margin of the Central Main Ethiopian Rift- A case study in the Belesa area, eastern Lemmo Woreda, Ethiopia

Electrical resistivity and magnetic methods in mapping groundwater on the western margin of the Central Main Ethiopian Rift- A case study in the Belesa area, eastern Lemmo Woreda, Ethiopia

Geology, mineralogy, geochemistry and genesis of volcano-sedimentary hosted Lake Abiyata diatomite in central main Ethiopian Rift

The Abiyata Diatomite deposit is located in the Main Ethiopian Rift, which is characterized by strong extensional tectonics. The deposit is mostly made up of diatomaceous earth, which is a sedimentary rock made up of the fossilized remnants of diatoms, which are tiny algae. Diatomite's geological, geochemical, and mineralogical features, as well as its formation, are discussed in this research. To characterize diatomite from Abiyata, chemical, mineralogical, technological, and micro paleontological examinations were conducted on samples collected from outcrops and stream sections. The XRD characteristic peaks of diatomite demonstrate that it is primarily made up of Opal A silica, however certain crystalline phases were discovered in adequate amounts. Quartz and feldspar were the predominant crystalline phases, with lesser amounts of Calcite, Cristobalite, Illite, Mordinite, Wairakite, Halloysite, Clinoaptilolite, Adularia, and Tridymite. From SEM photomicrographs diatomites are primarily formed of benthic freshwater diatom species such as Staurosirella pinnata, Staurosira construens, Pseudostaurosira brevistriata, Epithemia Sorex and surirella pinnata. Diatom species, sedimentary profile sections and mineralogical data suggest that diatomite was deposited in lacustrine-type freshwater shallow lake environment. Chemical data obtained from 10 diatomite samples show that while silica is the bodybuilding material for diatomite. i.e., Silica (SiO2), 76.9 %; Alumina (Al2O3), 3.49 %; Sodium Oxide (Na2O), 1.52 %; Potassium Oxide (K2O), 1.107 %; Iron Oxide (Fe2O3), 1.1 %; Loss on ignition (LOI) 13.7 and other oxides are below 1 %. Studies from technological properties like physical tests, chemistry, and mineralogy and micropaleontology of Abiyata diatomite suggest that calcined diatomite can be used for waste treatment processes in the filter aid industry and as filler material.

Occurrence of microplastics in commercial fish species from the Ethiopian rift valley's Lake Hawassa, Ethiopia.

Microplastics (MPs) have recently been detected as emergent pollutants in the Ethiopian rift valley lakes located close to rapidly expanding towns. We provide the first study of MPs ingestion of commercial fish species from Lake Hawassa, Ethiopia: Catfish (Clarias gariepinus) and Nile Tilapia (Oreochromis niloticus). A total of 60 individual fish species was collected from three sampling sites of lake Hawassa in October 2020. Across all sampling sites, there was a significant difference in ingested MPs between benthic omnivore catfish and pelagic phytoplanktivorous Tilapia (χ2 = 15.864, p < 0.001). The most common size of ingested MPs (84.6%) was 0.5-1mm, with fragments (59.5%) dominating, followed by fibers (25.4%). On average, 4.03 ± 1.33 MPs with sizes ranging between 60μm and 10.53mm were detected per individual. White and yellow MPs were particularly numerous, accounting for 36.8% and 26.4% of the total, respectively. Because Lake Hawassa's fishery is so significant, the potential impact of MP pollution on the lake biota in general, and economically valuable fish species in particular, deserves attention, additional research, and, if possible, early mitigation.

Geospatial analysis of volcano-tectonic interactions: implications for spatiotemporal variations in water quality and quantity at Lake Beseka, East Africa, Ethiopia

ABSTRACT Water quality deterioration in the Main Ethiopian Rift Lakes is a problem affecting the area’s public health and socioeconomic development. The present study aimed to assess the water level rise in Lake Beseka using Landsat images from 1975 to 2023 and dilution trends at the pumping site from 2004 to 2022. In addition, the spatial water quality parameters, including pH, EC, TDS, and water surface temperature, for the years 2007, 2018, 2021, and 2023 were determined. The water level increased dramatically from 3 km2 in the 1960s to 27.5 km2 in 1980 following the construction of the Koka dam and the beginning of irrigation activity (sugarcane plantation) for the Metehara sugar estate factory. The water level reached a maximum (50 km2 in the dry season) in the mid of 1910s and become decreased and fluctuated after 2015. The observed pH, EC, and TDS were higher in the central portion of the lake, grouped under brackish water, and lower in the southwest, south, and northeast shores. The EC and TDS were higher in 2007, decreased in 2018, and fluctuated. The geothermal anomaly of the area varies from 23.1 to 47.9°C with the highest anomaly occurring at the northern side of the lake at a recent volcanic area that interlinked with geological structures. However, the observed and estimated water temperatures of the lake decreased from west to east due to hot spring discharge from the southwest shore of the lake. The series of hot springs in the southwest and west shores of the lake with high discharge rates indicate the presence of structural connectivity that leads to the emission of heat from a deep-seated source and heated groundwater of the area recharged from irrigation activity. Overall, spatiotemporal lake water quality variations were due to anthropogenic and geogenic factors, including hot springs and groundwater discharge to the lake, water level rise and bathymetric depth variation, evaporation, and irrigation activity. This study is significant in continuously estimating water level fluctuations and providing early warnings and preparedness to maintain the region's socioeconomic development.

Rift and plume: a discussion on active and passive rifting mechanisms in the Afro-Arabian rift based on synthesis of geophysical data

Abstract. The causal relationship between the activity of mantle plumes and continental break-up is still elusive. The Afro-Arabian rift system offers an opportunity to examine these relationships, in which an ongoing continental break-up intersects a large Cenozoic plume-related flood basalt series. In the Afar region, the Gulf of Aden, the Red Sea, and the Main Ethiopian Rift form an R-R-R triple junction within plume-related flood basalt series. We provide an up-to-date synthesis of the available geophysical and geological data from this region. We map the rift architecture in the intersection region by applying the difference in Gaussians to the topography and the bathymetry and interpreting vertical gravity gradients and Bouguer anomalies. With the aid of these methods we review the spatiotemporal constraints in the evolution of the different features of the plume–rift system. Our results show rough and irregular morphologies of the Gulf of Aden and the Red Sea arms in contrast to the symmetric, continuous, and smooth Main Ethiopian Rift. The triple junction formed by the northeastward propagation of the Main Ethiopian Rift and developed simultaneously with the abandonment of the tectonic connection between the Red Sea and the Gulf of Aden through Bab al Mandab Strait. The triple junction was the last feature to develop in the plume–rift system and marked a tectonic reorganization. By this time, all rift arms were sufficiently evolved and the break-up between Africa and Arabia was already accomplished. We argue that the classical active and passive rifting mechanisms cannot simply explain the progressive development of the Afro-Arabian rift. Instead, we propose a plume-induced plate rotation, which includes an interaction between active and passive mechanisms. In this tectonic scenario, the arrival of the Afar plume provided a push force that promoted the rotation of Arabia around a nearby pole located to the northwest of the plate boundary, enabling the rifting and, ultimately, the break-up of Arabia from Africa.

Lithostratigraphy and Petrography of Mesozoic Sedimentary Rocks of Lemi Area, North Shewa, Central Ethiopia

The Mesozoic sedimentary basins in Ethiopia, particularly the Central Ethiopia, and Blue Nile Basin within the central main Ethiopian rift region are characterized by a diverse range of volcano-sedimentary rocks dominated by sedimentary sequences. The lithostratigraphy and petrology of Mesozoic sedimentary rocks of Lemi area, North Shewa, in Central Ethiopia within the Blue Nile basin, is described based on detailed field observations, lithostratigraphic analysis, petrographic examinations. The lithological units identified during fieldwork include Mudstone, Sandstone, and Basaltic rock formations. The sandstone unit in the study covers an estimated average thickness is 237 meters with intercalations of thinly bedded mudstone. The average thickness of each sandstone units (coarse (23 meters), medium (90 meters) and fine-grained (115 meters) sandstone unit) are varying from place to place within the study area. The stratigraphic section logs in four each block (Geza Washa, Dalota, Ruka, and Gosh Wiha) shows coarsening upward indicating the depositional environment transition from deep marine to the fluvial environment. The results of the study reveal the geological history and paleoenvironmental conditions of the Mesozoic sedimentary rocks in the Lemi area. This study contributes to our understanding of the geological processes that have influenced the formation of the Lemi area and provides valuable interpretations of regional geology.

Seamless Map of Depth to the Moho Interface in the Afro‐Arabian Region Using Gravity Data Derived From EGM2008

AbstractThe Afro‐Arabian region is one of the few places on land, where rifting processes at divergent plate boundaries can be thoroughly investigated. One of the crucial factors in understanding rifting processes involves assessing the crustal thickness. In this study, gravity data from the Earth Gravitational Model 2008 is used to create a seamless map of the depth to the Moho interface. Unlike many previous investigations that focused on specific localized areas, within the region, results from the current study provide a comprehensive view. The depth obtained from the current investigation aligns well with findings from earlier studies, exhibiting a bias of 0.69 km and a standard deviation of 3.89 km. Within the region, maximum and minimum depths to the Moho interface are observed beneath the northwest Ethiopian Plateau and the Gulf of Aden Rift (GAR), respectively. Analyzing profiles across the Red Sea, Main Ethiopian, and GARs, the study concluded that the Southern Main Ethiopian Rift is in an earlier stage of the rifting process, while the GAR is at an advanced stage. Furthermore, the interpretation of the current findings led to the inference that there might exist two potential plume tails driving the rifting process in the East Africa Rift—one originating from the Afar region and the other from South Kenya. This inference primarily relies on the isostatic compensation stages observed in the various rift systems throughout the region.

The subsurface anatomy of a mid-upper crustal magmatic intrusion zone beneath the Boku volcanic complex, Main Ethiopian Rift inferred from gravity data

Strain accommodation in the Main Ethiopian Rift has been localized since the Quaternary in axial magmatic segments that contain magma intrusion, volcanic complexes, and fault zones. However, the crustal structure and magmatic plumbing features of the individual volcanic complexes within these magmatic segments are poorly constrained. In this study, gravity data from the Global Gravity Model plus2013 was used to interpret the crustal structure and subsurface volcanic network at and near the Boku Volcanic Complex (Boku VC). Two-dimensional gravity models and an upward continuation map analysis of the upper crust reveal a gravity maximum that is interpreted as mafic intrusion at depths between 5 and 10 km beneath the Boku VC. A circular gravity maximum on the upward continued and residual gravity anomaly maps over the Boku VC and adjacent segments suggest the shallow plumbing systems beneath the segments are discrete, but that they merge into the deeper crust. The gravity models suggest that below 5 km beneath the center of magmatic segments nearly all the extension over the last 2 My can be accounted for by magmatic intrusion. Our models require faults in the uppermost crust which likely contribute to extension and may serve locally as conduits for the conveying melts or hydrothermal fluids. Our gravity analysis supports petrological studies that indicate a two-level magmatic plumbing system beneath the Wonji fault belts in which a melt supply from the upper mantle moves to mid-crust and then to shallow upper crust where the magma fractionates into more siliceous magma within smaller magma chambers.

Flood hazard analysis and risk assessment using remote sensing, GIS, and AHP techniques: a case study of the Gidabo Watershed, main Ethiopian Rift, Ethiopia

This research aimed to evaluate flood hazards and risk areas in the Gidabo Watershed using remote sensing (RS), Geographic Information Systems (GIS), and analytical hierarchy process (AHP). Six main factors were considered to identify flooding hazard zones: drainage density (DD), soil, elevation, rainfall, slope, and land use land cover (LULC). Population density, flood hazard zone, and LULC were considered for mapping the flood risk zone in the Gidabo watershed. A weighted overlay analysis tool has been utilized to integrate the thematic layers to identify both flood hazard and flood risk zones. The findings indicated that about 41.6% (337 km2) of the watershed falls within the high and very high flooding hazard zones. Conversely, 31.11% (252 km2) of the watershed is categorized under very-low and low flooding hazards. Moreover, the study identified five flood risk zones in the area viz; very high, high, moderate, low, and very low. The result of the flood risk map revealed that 199.5 km2 (24.5%) of the watershed has a higher and very higher risk of flooding. These zones were validated using the receiver operating characteristic (ROC) curve, showing a correlation coefficient of 0.943. These results emphasize the need to implement prediction of floods, early warning systems, and effective management practices on a regular and sustainable basis.

The Dynamic Crust of Northern Afar and Adjacent Rift Margins: New Evidence From Receiver Function Analysis in Eritrea and Ethiopia

AbstractAfar 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 &gt;1.9, demonstrating that magma‐assisted extension continues to be important in the final stages of continental breakup.

Spatial interpolation techniques comparison and evaluation: The case of ground-based gravity and elevation datasets of the central Main Ethiopian rift

The ground-based gravity data reveals diverse anomaly signatures in areas of the Main Ethiopian rift where active volcanic and tectonic activities are dominant. In such a region ground-based data collection is restricted to existing roads and relies on accessible stations. These resulted in gaps in data, either missing, uneven, or insufficient spatial coverage that must be estimated with proper interpolation techniques. Comparison and evaluations of the spatial interpolation methods that are commonly used in potential field geophysical data analysis were made for the terrestrial gravity and elevation data of the central Main Ethiopian rift. In this research, two widely used interpolation techniques, minimum curvature interpolation, and Ordinary Kriging were compared and assessed. A 10 % hold-out validation was employed, where 90 % of the data points were used to generate interpolated surfaces, which were then evaluated against the remaining 10 %. Following interpolation with each technique, the generated grid was converted into discrete data points (estimated values). These are then compared with the available gravity data, which were deliberately excluded from the gridding process (10 % remaining dataset). The accuracy of each method was assessed by evaluation metrics such as mean value, variance, Mean Absolute Error (MAE), Root Mean Square Error (RMSE), correlation coefficient (r), and R-squared. The results showed that the ordinary Kriging interpolation method outperformed the minimum curvature interpolants for gravity data with all performance metrics, while both interpolants seem to perform equally well for the elevation dataset. Therefore, it is proposed to use the Kriging interpolation method for potential field gravity studies conducted in the central Main Ethiopia rift.