African Rift Valley Research Papers (original) (raw)

2025, Tectonics

Our understanding of how magma‐poor rifts accommodate strain remains limited largely due to sparse geophysical observations from these rift systems. To better understand the magma‐poor rifting processes, we investigate the lithospheric structure of the Malawi Rift, a segment of the magma‐poor western branch of the East African Rift System. We analyze Bouguer gravity anomalies from the World Gravity Model 2012 using the two‐dimensional (2‐D) radially averaged power‐density spectrum technique and 2‐D forward modeling to estimate the crustal and lithospheric thickness beneath the rift. We find: (1) relatively thin crust (38–40 km) beneath the northern Malawi Rift segment and relatively thick crust (41–45 km) beneath the central and southern segments; (2) thinner lithosphere beneath the surface expression of the entire rift with the thinnest lithosphere (115–125 km) occurring beneath its northern segment; and (3) an approximately E‐W trending belt of thicker lithosphere (180–210 km) ben...

2024, Journal of Geophysical Research: Solid Earth

To investigate the mechanisms for the initiation and early‐stage evolution of the nonvolcanic southernmost segments of the East African Rift System (EARS), we installed and operated 35 broadband seismic stations across the Malawi and Luangwa rift zones over a 2 year period from mid‐2012 to mid‐2014. Stacking of over 1900 high‐quality receiver functions provides the first regional‐scale image of the 410 and 660 km seismic discontinuities bounding the mantle transition zone (MTZ) within the vicinity of the rift zones. When a 1‐D standard Earth model is used for time‐depth conversion, a normal MTZ thickness of 250 km is found beneath most of the study area. In addition, the apparent depths of both discontinuities are shallower than normal with a maximum apparent uplift of 20 km, suggesting widespread upper mantle high‐velocity anomalies. These findings suggest that it is unlikely for a low‐velocity province to reside within the upper mantle or MTZ beneath the nonvolcanic southern EARS....

2024, Frontiers in Earth Science

2024

The author in his paper titled "The Appearance of Adam from the Quranic Perspective-Creation or Evolution? suggested that the creation of Adam (AS) took place through an evolutionary process. The objective of this paper was to present the path the evolutionary process took for his appearance.
We propose that Adam(AS) was the father of Homo erectus. He appeared about 1.6 to 1.9 million years ago and likely evolved from Homo habilis or from a late form of Australopithecus in Africa. Since most of the fossils of Homo habilis and his predecessors are found in East African Rift Valley, we suggest that he was born in East African Rift Valley, which is located in East Africa.
He was conceived in one of the human-looking females in a manner similar to the way Isa(AS) was conceived. The birth of Adam(AS) followed the same course, as it did with the birth of Isa(AS). Allah(ST) taught him to speak as He did to Isa(AS) after his birth. After he grew up, Allah(ST) created his mate (Hawwa(AS)) from him and a human looking female through a natural biological process. She (Hawwa(AS)) must have had the same human characteristics as Adam(AS) had, which their mothers did not have. After demonstrating his superiority over the angels, Adam(AS) and Hawwa(AS) were given residence in a garden, which we propose was Bahir Dar. It is about 200 miles northwest of Adis Ababa, the capital of Ethiopia, at an elevation of about 6,000 feet. When they ate the fruit of the forbidden tree there, they were relocated back to the East African Rift Valley. From there his progeny spread throughout the world.

2024, In: L. E. Frostick, et al. (eds). Sedimentation in the African Rifts. Geological Society Special Publications, 25

A broad overview of the present landforms of the African Rift system and the relationship between the rift basins.

2024, Contextos Revista De Humanidades Y Ciencias Sociales

RESUMEN El presente documento tiene como objetivo cuestionar la tesis por la cual se presenta la doble negación que hay sobre el canibalismo en la etapa paleolítica y principios del neolítico, en cuanto a su existencia como comportamiento humano y como pauta cultural de conducta, que se encuentran presentes en el libro El Banquete Humano del español Luis Pancorbo (2009). Este texto, como síntesis bibliográfica, pretende enfrentarse, desde una interpretación quizá audaz, a estas negaciones que se hacen de una de las particularidades históricas del ser humano, sobre una fundamentación que está condicionada por las características de las evidencias que se exponen de los hechos.

2024, Geoarchaeology

The site of Mwanganda's Village, located along a paleochannel in northern Malawi, is one of only a few sites that have characterized the Middle Stone Age (MSA) of Malawi for decades (Clark & Haynes, ; Clark et al., ; Kaufulu, ). The Malawi Earlier‐Middle Stone Age Project has re‐examined the site using new mapping and chronometric tools in order to reinterpret the site's significance within the context of current debates surrounding human origins and the potential role the environment played in shaping human behavior. The new data do not support the previous hypothesis that the site was an elephant butchery location (contra Clark & Haynes, ; Clark et al., ; Kaufulu, ). Instead, the evidence shows successive colonization of riparian corridors by MSA hunter‐gatherers focused on exploiting localized resources during periods of generally humid climates while other lakes desiccated across Africa. We challenge the hypothesis that stable and intermediately high lake levels within t...

2024

9. Raus aus Arabien (70 – 75 ka) ……………………………..…... 1
9.1 Der große menschliche Flaschenhals ………………………….. 2
9.2 Übergang Mittel-Jungpaläolithikum …………………….…….. 3

2024

9. Out of Arabia (70 – 75 ka) …………………………….…... 1
9.1 The Great Human Bottleneck ……………………….…….. 2
9.2 Middle-Upper Palaeolithic Transition …………………….. 3

2024

Menschwerdung (300 – 100 ka) …………………….….............……….. 1
7.1 Saat der Moderne …….……………………………………..................….. 1
7.2 Übergang vom unteren zum mittleren Paläolithikum ……... 3
7.2.1 Gehirnleistung …………………………………………...........……………… 3
7.2.2 Vorbereitete Kerntechnologien ………………………….......………. 4
7.3 Fehlende Glieder in Arabien …………………………………..........……. 5
7.4 Unsere Entstehung ………………………………………………............……. 6
7.4.1 Meinungen sind wie unser Kinn …………………………….......…… 6
7.4.2 Revolution des Verhaltens …………………………………...........…… 8

2024

6. Wurzeln des menschlichen Stammbaumes (3.3 ma – 300 ka) .… 1
6.1 Praktische Menschen ………………………………………........................……. 2
6.1.1 Werkzeugbau, Gehirngröße und Subsistenz ……….............……….. 3
6.1.2 Landschaftsverzänderung im Rift Valley ……………….............….... 4
6.1.3 Ein riesiger Sprung ……….……….…………………............................……… 5
6.2 Homo erectus …………………………….………….............................………....….6
6.2.1 Kreativität ………………………….…………………….….................................… 6
6.2.2 Nach Arabien ……………………………………................................….……….. 7
6.3 Homo heidelbergensis ………………………..........................…………………… 8
6.3.1 Zündung ………………………………………………...................................………. 8
6.3.2 Arabisches Acheuléen …………………………….......................……………. 10

2024

6. Roots of the Human Tree (3.3 ma – 300 ka) … 1
6.1 Handy Humans …………................……………………. 2
6.1.1 Toolmaking, Brain Size, and Subsistence … 3
6.1.2 Landscape Bias in the Rift Valley ……....….... 4
6.1.3 One Giant Leap ……….……….……...............……… 5
6.2 Homo erectus ………………………................…….…….6
6.2.1 Creativity ……………………...................…….………… 6
6.2.2 Into Arabia ………………………..................………….. 7
6.3 Homo heidelbergensis …………….............,………… 8
6.3.1 Ignition ……………………………....................…………. 8
6.3.2 Arabian Acheulean …………………….............……. 10

2024, African Journal of Ecology

2024, Naturaleza y libertad. Revista de estudios interdisciplinares

En este artículo se propone la utilidad de un abordaje desde la cor-poralidad para el análisis del pasado prehistórico y, fundamentalmente, del pro-ceso de hominización. En este sentido, se abordan tres procesos: el surgimiento de la bipedestación, la producción de las primeras herramientas de piedra y el posible origen del lenguaje a partir de la gestualidad motora. Se considera que estas adaptaciones no pueden reducirse a meras expresiones físicas del pensa-miento, y que deben entenderse como técnicas corporales aprendidas mediante un largo proceso de experimentación a partir de modos somáticos de atención. De esta manera, se pretende abordar los aspectos biológico y cultural de la evo-lución como inconmensurables de la experiencia humana.

2024, International Journal of Innovation and Applied Studies

The Nyamulagira volcano enters in eruption approximately each 2 years and the last eruption of November 06, 2011 was started 22 months after that of January 02, 2010. The aim of this work is the characterization of some aspects of seismicity prior the Nyamulagira eruption on 2011by temporal analysis of the hypocenters (epicenters and depths), earthquake number and spectral frequency. A temporal evolution showed that the seismicity rate, the hypocenters, the corner frequency and energies release vary and give a comprehension of the behavior of the volcanic activity. 10 months before the eruption, earthquakes were deep (10-30 km) and scattered with weak corner frequencies (< 2.6 Hz) in the field of Nyamulagira. That confirms a partial melt or deep magmatic intrusion with weak displacement. The magmatic migration starts between April and October 2011 with shallow earthquakes (0-5 km) and high corner frequency and high energy. This period prepares a pathway of magma to the surface. The frequency and energy were then higher in the last swarms of 04 and 05 November 2011, 2 days prior the eruption. This last seismicity denote at the same time a magmatic intrusion, a fracturing of the weakness zones and an extrusion of the lava at the surface. A deep investigation of these parameters on several eruptive cycles would facilitate the knowledge of the magmatic dynamics of Nyamulagira volcano and also the predictive approach of its eruptions.

2023, Nature Geoscience

When continents are stretched over a long period of time, deep elongated rift valleys form at Earth's surface and zones of ponded magma, centred beneath the rift, form at the crust-mantle boundary 1,2. Ascending magma sometimes erupts within the rift valley 3,4 or, counterintuitively, at volcanic fields away from the rift valley that are o set by tens of kilometres from the source of magma at depth 5-8. The controls on the distribution of this o-rift volcanism are unclear. Here we use a numerical model of magmatic dyke propagation during rifting to investigate why some dykes reach the surface outside the rift valley, whereas others are confined to the valley. We find that the location of magmatism is governed by the competition between tectonic stretching and gravitational unloading pressure, caused by crustal thinning and faulting along the rift borders. When gravitational unloading dominates over tectonic stretching forces, dykes ascending from the ponded magma are steered towards the rift sides, eventually causing o-rift eruptions. Our model also predicts the formation of stacked magma sills in the lower crust above the magma-ponding zone, as well as the along-rift propagation of shallow dykes during rifting events, consistent with observations of magmatism and volcanism in rift zones globally. We conclude that rift topography-induced stress changes provide a fundamental control on the transfer of magma from depth to the surface. Continental rifts are commonly flanked by magmatism during their early stages 5,6. In the Miocene-Recent Main Ethiopian Rift (MER), for example, many Pliocene volcanoes lie outside the Miocene rift border faults 9,10 (Fig. 1). As the cumulative extension has increased, magmatism has become focused within the rift axis 3. A similar pattern is observed during the evolution of the Red Sea Rift, where ∼25-Myr-old rift-parallel dykes focus near the ∼30-Myr-old rift margins and the youngest volcanoes focus along the ridge axis 11. Even in far less magmatically active settings, such as the Baikal Rift (Siberia) or the Chaine des Puys (CdP) in the Cenozoic rift system of France, off-rift volcanism occurred after the onset of rifting 7,8. During rift initiation, the lithosphere thins by ductile stretching beneath a rift valley formed from normal faulting 12. The upwelling asthenosphere melts by adiabatic decompression, with the greatest degree of partial melting beneath the most thinned rift valley 1,2. Although most studies focus on in-rift magmatism 3,4 , a model is needed to explain how off-rift volcanoes are fed. Progressive rift spreading results in the oldest volcanoes being transported away from the rift axis. However, such a process does not explain off-rift volcanism, with volcanoes located outside the rift border faults. Previous models for off-rift volcanoes include low-angle

2023, Advances in traditional medicine

This study documented use of wild food and medicinal plants in areas around five biodiversity hot spots in Zimbabwe. Data was collected using semi-structured interviews and focus group discussions in representative communities. About 89 wild food plants were used by the communities. Trees, shrubs, tubers/herbs, lianas/climbers and succulents constituted 65%, 11%, 12%, 8% and 4% respectively. Fruits were mostly harvested (52%) then leaves (28%), and others (roots/rhizomes/tubers, sap and fibres) (20%). Fruits were commonly consumed raw (96%) whilst others are processed into juices (4%), mostly collected by women and children. Fruits of Adansonia digitata L., Vangueria infausta Burch., Uapacca kirkiana Müll. Arg., Berchemia discolour/zeyheri (Klotzsch) Hemsl., Vitex doniana Sweet and leaves of A. digitata were most preferred plant species because of their taste and availability. However, some fruits such as Vitex spp. and U. kirkiana caused constipation and diahorrea respectively if consumed in excess. About 149 medicinal plant species belonging to 115 genera and 61 families were used for treating about 32 diseases and disorders. These were dominated by families; Fabaceae(16%), Meliaceae(5%), Apocenaceae(3%), Anacadaceae(3%) and Solanaceae (4%). About 45, 30, 25, 23, 13 species treat abdominal pains, toothache, women and gynaecological issues, sexually transmitted diseases and paediatric remedies respectively. Other species are used as aphrodisiacs (4) and treatment of cancer (4). Leaves (28%), roots(27%) bark(24%) and fruits(12%) were main parts used to prepare remedies. Cultural/Traditional knowledge plays an important role in valuing species in particular areas and associated conservation of food and medicinal plants.

2023, Geology

Upper mantle seismic velocity variations beneath northern Tanzania coupled with the structure of the 410 and 660 km discontinuities reveal a 200-400-km-wide thermal anomaly extending into but not necessarily through the transition zone beneath the eastern branch of the East African rift system. This finding is not easily explained by small-scale mantle convection induced by passive stretching of the lithosphere or by a broad thermal upwelling extending from the lower mantle into the upper mantle, but it can be attributed to a mantle plume, provided that a plume head is present under the lithospheric keel of the Tanzania craton. A plume interpretation for the deep thermal anomaly is supported by evidence for mantle having the geochemical characteristics of a plume at >150 km depth beneath northern Tanzania.

2023, Journal of Geophysical Research: Solid Earth

We present 10 min resolution crust and lithosphere maps of Africa constrained by a compilation of seismic Moho data and tomography models. 2) Our maps cover large areas of Africa where no data are available showing 76% fit with seismic data after excluding the Afar plume region. 3) Misfits with seismic data in the Afar region are discussed in terms of residual topography related to sublithospheric processes. Abstract 1. Introduction 2. Tectonic Background 3. Data 4. Method and model parameters 5. Results

Hovers, E., 2023. Hadar, Ethiopia, in: Beyin, A., Wright, D.K., Wilkins, J., Olszewski, D.I. (Eds.), Handbook of Pleistocene Archaeology of Africa : Hominin Behavior, Geography, and Chronology. Springer, pp. 373-385. https://doi.org/10.1007/978-3-031-20290-2_22

2023, Handbook of Pleistocene Archaeology of Africa

The Hadar Research Project area (HRP) is a c. 100 km2 area in the Afar region in northeastern Ethiopia. Best known for its Pliocene (3.45–2.9 Ma) hominin fossils and fauna, stone artifact-bearing sites have been documented in Hadar since the 1970s. A majority of artifacts were found as eroded surface finds. Few “Middle Acheulean” and Oldowan finds were reported as in situ occurrences, some of which) were later incorporated in the Gona project and explored under its auspices. Additional sites in the HRP were discovered and systematically excavated between 1994 and 2011 by members of the HRP, and have been under study since. All the currently known archaeological localities in the Hadar research area are found in sediments of the previously designated upper Kada Hadar (KH) member of the Hadar Formation, now subsumed into the pan-Afar depression Busidima Formation (BF).

2023, Geophysical Journal International

The thickness of the mantle transition zone beneath Cameroon has been mapped using data from the 2005-2007 Cameroon Broadband Seismic Experiment to evaluate models for the origin of the Cameroon Volcanic Line (CVL). Some 2200 receiver functions have been stacked using a 3-D velocity model, revealing P s conversions from the mantle transition zone discontinuities at depths of ∼410 and 660 km. Results yield a nearly uniform transition zone thickness (251 ± 10 km) that is similar to the global average, implying that any thermal anomalies in the upper mantle beneath the CVL do not extend as deep as the transition zone. This finding, when combined with regional P and S velocity models of the mantle, supports an explanation attributing the origin of the CVL to upper mantle processes such as an edge flow convection cell in the upper mantle along the northwestern side of the Congo Craton lithosphere.

2023, Environnemental and Earth Science Research Journal

The Karibumba region, in the Mesoproterozoic Kibaran chain, is one of the least geochemically and metallogenically known regions of Kivu. Moreover, the Kibaran chain is geochemically characterized by valuable content of tin (Sn), tantalum (Ta), niobium (Nb), tungsten (W), lithium (Li), gold (Au), and rare earth elements (REE). With the belonging of Karibumba in this chain, it is likely that valuable occurrences of these elements can be found in this entity. In addition, these metals and rare earth elements are largely used nowadays by modern industries and green technologies. This increases even more and in an exponential way the demand for these metals. It is to constrain the geochemical and metallogenic aspects that this study was carried out in the Karibumba area in the territory of BENI, eastern Democratic Republic of Congo (DRC). To achieve this, geological studies and fieldwork allowed to collect samples which were geochemically analysed for trace element. These samples were selected based on petrographic facies variation. Trace elements were determined by a combination of X-ray fluorescence spectrometry (XRF) and inductively coupled plasma mass spectrometry (ICP-MS). Results revealed that, the only mineralization identified with certainty in the Karibumba area is gold. The other elements analyzed showed grades lower than or comparable to the Clarkes and constitute the geochemical background of the area. The anomalous tin content in sample JM01 and the significant negative correlation between gold and silver raise the need for further study in the area. This would identify the nature of the stanniferous anomaly found and cross-check the surprising negative correlation between gold and silver.

2023, Geophysical Journal International

The Indochina block is important to our understanding of the extrusion model as a consequence of the Indo-Eurasia collision. The lithospheric structure of this block, however, remains obscured due to a lack of sufficient instrumentation for high resolution seismic imaging. We present a shear velocity model derived from Rayleigh wave phase velocity tomography using data from recently deployed seismic networks in this region. Our inversion results for lithospheric structure show strong correlations with tectonic history in this block. A prominent slow-velocity anomaly (5 per cent) is observed in northern Indochina along the Ailao Shan-Red River (ASRR) shear zone including Chuxiong basin, Lanping-Simao fold belt and Thailand rift basin, which has seen extensive deformation events since Eocene. The Khorat Plateau basin is characterized by thick continental keel type lithosphere, consistent with palaeomagnetic and geological observations indicating this basin has experienced much less deformation than the surrounding regions. Additionally, our inversion imaged a sharp, lithospheric-scale velocity contrast across the southeastern segment of ASRR, indicative of a thin and thus relatively weak lithosphere southwest of Red River Fault. The thin lithosphere, low asthenospheric seismic velocities we observe and the average crustal thicknesses in the region suggest that the topography high is dynamically supported by upwelling asthenosphere rather than thickening of the crust/lithosphere. Based on the occurrence of Palaeogene volcanism and its timing, we prefer an explanation of thinning of the lithosphere and allowing a throughgoing fault rather than emplacement of a thin terrane to explain the thin lithosphere. Therefore, the anomalously thin lithosphere between Khorat Plateau and the ASRR in conjunction with other geological observations is generally consistent with the extrusion model for Indochina, which requires localization of lithospheric deformation around tectonic blocks.

2023

To investigate the mechanisms for the initiation and early-stage evolution of the nonvolcanic southernmost segments of the East African Rift System (EARS), we installed and operated 35 broadband seismic stations across the Malawi and Luangwa rift zones over a 2 year period from mid-2012 to mid-2014. Stacking of over 1900 high-quality receiver functions provides the first regional-scale image of the 410 and 660 km seismic discontinuities bounding the mantle transition zone (MTZ) within the vicinity of the rift zones. When a 1-D standard Earth model is used for time-depth conversion, a normal MTZ thickness of 250 km is found beneath most of the study area. In addition, the apparent depths of both discontinuities are shallower than normal with a maximum apparent uplift of 20 km, suggesting widespread upper mantle high-velocity anomalies. These findings suggest that it is unlikely for a low-velocity province to reside within the upper mantle or MTZ beneath the nonvolcanic southern EARS....

2023, Geophysical Journal International

The crustal structure surrounding the northern Malawi rift and beneath the Rungwe Volcanic Province (RVP) has been investigated using teleseismic earthquakes recorded on SEGMeNT broad-band seismic stations to determine the extent to which the crust has been modified by Cenozoic rifting and magmatism. The SEGMeNT network included 57 broad-band seismic stations deployed in northern Malawi and southern Tanzania between August 2013 and October 2015. Estimates of crustal thickness, shear wave velocity and Poisson's ratio have been obtained by modelling P-wave receiver functions using the H-k stacking method and jointly inverting receiver functions with Rayleigh wave phase velocities. These estimates are used to investigate the extent of magmatic modification to the crust, indicated by changes in Poisson's ratio, and the geometry of crustal thinning along the northern margins of the Malawi rift and beneath the RVP. The average crustal thickness for the four stations in the RVP is 39 km, the average Poisson's ratio is 0.28 (Vp/Vs = 1.83), and the average crustal shear wave velocity is 3.6 km s-1. Although the RVP has been a site of ongoing magmatism since at least 17 Ma and is associated with a pronounced low velocity zone in the mantle, our results show little evidence that the bulk composition or thickness of the crust beneath the RVP has been significantly modified by magmatism or extension. However, Poisson's ratios of 0.29-0.31 (Vp/Vs = 1.85-1.91) at three of the stations in the RVP, where there is also no evidence for higher Vs, may indicate the presence of partial melt in the crust. The average crustal thickness of Proterozoic terranes surrounding the northern end of the Malawi rift ranges from 38 to 42 km. For most of the terranes, average Poisson's ratios are between 0.25 and 0.26 (Vp/Vs = 1.73-1.76), with the exception of the Irumide Belt, which has an average Poisson's ratio of 0.23 (Vp/Vs = 1.68). The average crustal shear wave velocities for all the terranes are either 3.6 or 3.7 km s-1. These results indicate a bulk felsic to intermediate crustal composition for all terranes, consistent with previous results, and reveal that there is little, if any, crustal thinning beneath the uplifted flanks of asymmetric basins within the northern Malawi rift or beneath the RVP. Consequently, crustal thinning in the northern Malawi rift must be highly focused beneath the centres of rift basin segments, consistent with models of rift flank topography and gravity observations.

2023, Geochemistry, Geophysics, Geosystems

P and S wave tomographic models have been developed for the northern Malawi rift and adjacent Rungwe Volcanic Province (RVP) using data from the Study of Extension and maGmatism in Malawi aNd Tanzania project and data from previous networks in the study area. The main features of the models are a low-velocity zone (LVZ) with δVp =~À1.5-2.0% and δVs =~À2-3% centered beneath the RVP, a lower-amplitude LVZ (δVp =~À1.0-1.3% and δVs =~À0.7-1%) to the southeast of the RVP beneath the center and northeastern side of the northern Malawi rift, a shift of the lower-amplitude anomaly at~À10°to À11°to the west beneath the central basin and to the western side of the rift, and a fast anomaly at all depths beneath the Bangweulu Craton. The LVZ widens further at depths >~150-200 km and extends to the north beneath northwestern Malawi, wrapping around the fast anomaly beneath the craton. We attribute the LVZ beneath the RVP and the northern Malawi rift to the flow of warm, superplume mantle from the southwest, upwelling beneath and around the Bangweulu Craton lithosphere, consistent with high 3 He/ 4 He values from the RVP. The LVZ under the RVP and northern Malawi rift strongly indicates that the rifted lithosphere has been thermally perturbed. Given that volcanism in the RVP began about 10 million years earlier than the rift faulting, thermal and/or magmatic weakening of the lithosphere may have begun prior to the onset of rifting. Plain Language Summary P and S wave tomographic models have been developed for the northern Malawi rift and adjacent Rungwe Volcanic Province (RVP) using data from the Study of Extension and maGmatism in Malawi aNd Tanzania project and data from previous networks in the study area. A low-velocity anomaly is imaged under the RVP and northern Malawi rift. We attribute the low-velocity anomaly to flow of warm mantle from the African superplume to the southwest of the study area, which has migrated around the side of thick Bangweulu Craton lithosphere and upwelled beneath the thinner mobile belt lithosphere to the east of the Bangweulu Craton. The observation that volcanism began in the RVP prior to the onset of rifting suggests that the lithosphere beneath the Malawi rift may have been thermally weakened prior to rifting.

2023

The over 5000 m high Rwenzori Mountains are situated within the western branch of the East African Rift System, at the border between Uganda and the Democratic Republic of Congo. They represent a basement block within the rift valley whose origin and relation to the evolution of the EARS are highly puzzling. During 2006/2007 a network of 27 seismological stations was operated in this area to investigate crustal and upper mantle structure in conjunction with local seismicity. The data analysis revealed unexpectedly high microseismic activity. On average more than 800 events per month could be located with magnitudes ranging from 0.5 to 5.1. Hypocentral depths go as deep as 30 km with a pronounced concentration of activity at a depth of about 15 km. This presentation focuses on a cluster of seven earthquakes that were located at anomalous depths between 53 and 60 km. According to our present knowledge these are the deepest events so far observed within the EARS and the African Plate. Their origin might be connected to magmatic intrusions. However, the existence of earthquakes at this depth is enigmatic, especially within a rifting regime were one expects hot and weak material close to the surface, which is not capable of seismogenic deformation. We think that these events are closely related to the evolution of the Rwenzoris. A recent hypothesis to explain the extreme uplift of the Rwenzori Mountains is rift induced delamination (RID) of mantle lithosphere that is captured between two approaching rift segments. By numerical modelling we show that the RID-process is also able to bring material that is cold and brittle enough to release seismic energy into greater depth. Therefore the RID-mechanism gives a consistent explanation for the detected deep events as well as for the uplift of a mountain block in a rift setting.

2023, Journal of Volcanology and Geothermal Research

The Plinian eruption of the Wendo Koshe crater within the Corbetti Caldera occurred around 396 BC. The pumice lapilli deposit, with a thickness exceeding 10 cm, dispersed over an area of over 1000 km 2 around the towns of Hawasa and Shashemene. Most of the pumice was deposited by fallout ; however, minor local pyroclastic density currents also occurred. The calculated volume of preserved pumice fall deposit (approximately 1.2 km 3), combined with the estimated volume of dispersed fine ash distributed further from the volcano, corresponds to an estimated volume of 0.4 km 3 (dense rock equivalent) of erupted magma. The age of the pumice eruption (396 ± 38 BC) was determined by 14 C radiometric dating of a paleosoil that developed on previous pyroclastic deposits buried by the pumice. The majority of the post-caldera volcanic products are characterized by a relatively uniform chemical composition (TiO 2 = 0.24-0.27 wt.%, Zr = 1300-1600 ppm, ƩREE = 920-1150 ppm) without any significant development in composition. Despite the negligible variations in composition of the magmas that erupted during the last 2500 years within the Corbetti Volcanic System, a significant change in composition was documented prior to the 396 BC Wendo Koshe younger pumice eruption. The caldera stage ignimbrite of Corbetti (TiO 2 = 0.34 wt.%, Zr = 500 ppm, ƩREE = 370 ppm) and the early post-caldera obsidians are (TiO 2 = 0.34 wt.%, Zr = 800 ppm, ƩREE = 410 ppm) characterized by a commenditic composition, and the character of the rhyolitic magmas shifted towards pantellerites in the post-caldera stage. The compositional contrast is confirmed also by Sr isotope ratios. The Corbetti ignimbrite is characterized by being more radiogenic (87 Sr/ 86 Sr = 0.70678) than the post-caldera obsidians (87 Sr/ 86 Sr = 0.7046-0.7047). In contrast to the traceelement concentrations, the early Chabi obsidian does not differ from younger obsidians in isotope composition. Similarly to other silicic volcanic systems of the Main Ethiopian Rift, the rhyolitic magmas of the recently active volcanoes within the Corbetti Volcanic System are most likely produced by extreme fractional crystallization of basaltic melts.

2023, Frontiers in Earth Science

Density perturbations in the subsurface are the main driver of mantle convection and can contribute to lithospheric deformation. However, in many places the density structure in the subsurface is poorly constrained. Most geodynamic models rely on simplified equations of state or use linear seismic velocity perturbations to density conversions. In this study, we investigate the density structure beneath the Rungwe Volcanic Province (RVP), which is the southernmost volcanic center in the Western Branch of the East African Rift (EAR). We use shear-wave velocity perturbations (dlnv s) as a reference model to perform constrained inversions of satellite gravity data centered on the RVP. We use the code jif3D with a dlnv s-density coupling criterion based on mutual information to generate a 3D density model beneath the RVP up to a depth of 660 km. Our results reveal a conspicuous negative density anomaly (~−200 kg/m 3) in the sublithospheric mantle (at depths ranging from~100 km to~250 km) beneath the central part of the Malawi Rift extending to the west, beneath the Niassa Craton, coincident with locations with positive shearwave velocity perturbations (+7%). We calculate a 3D model of the velocity-todensity conversion factor (f) and find negative f-values beneath the Niassa Craton which suggests the observed negative density anomaly is mostly due to compositional variations. Apart from the Niassa Craton, there are generally positive f-values in the study area, which suggest dominance of temperature control on the density structure. Although the RVP generally shows negative density anomalies and positive f-values, at shallow depths (<120 km), f ≈ 0, which suggests important contributions of both temperature and composition on the density structure possibly due to the presence of plume material. The negative buoyancy of the Niassa Craton contributes to its long stability, while constituting a barrier to the southward flow of plume material, thus restricting the southward continuation of magmatism in the Western Branch of the EAR. The presence of a negative-density anomaly where dlnv s are positive is incompatible with models based on the use of simple dlnv s to density conversion factors. These results have implications on how dlnv s models are converted to density perturbations.

2023, Molecular Ecology

African mole-rats are subterranean Hystricomorph rodents, distributed widely throughout sub-Saharan Africa, and displaying a range of social and reproductive strategies from solitary dwelling to the 'insect-like' sociality of the naked mole-rat, Heterocephalus glaber. Both molecular systematic studies of Rodentia and the fossil record of bathyergids indicate an ancient origin for the family. This study uses an extensive molecular phylogeny and mitochondrial cytochrome b and 12s rRNA molecular clocks to examine in detail the divergence times, and patterns of speciation of the five extant genera in the context of rift valley formation in Africa. Based on a value of 40-48 million years ago (Myr) for the basal divergence of the family (Heterocephalus), we estimate divergence times of 32-40 Myr for Heliophobius , 20-26 Myr for Georychus / Bathyergus and 12-17 Myr for Cryptomys , the most speciose genus. While early divergences may have been independent of rifting, patterns of distribution of later lineages may have been influenced directly by physical barriers imposed by the formation of the Kenya and Western Rift, and indirectly by accompanying climatic and vegetative changes. Rates of chromosomal evolution and speciation appear to vary markedly within the family. In particular, the genus Cryptomys appears to have undergone an extensive radiation and shows the widest geographical distribution. Of the two distinct clades within this genus, one exhibits considerable karyotypic variation while the other does not, despite comparatively high levels of sequence divergence between some taxa. These different patterns of speciation observed both within the family and within the genus Cryptomys may have been a result of environmental changes associated with rifting.

2023, Journal of Zoology

Alongside the eusocial naked mole-rat, Heterocephalus glaber, Heliophobius argenteocinereus is the second oldest lineage within the African mole-rat family Bathyergidae, and phylogenetically intermediate between the East African H. glaber and the South African genera Bathyergus and Georychus. Across its geographic range H. argenteocinereus is widely distributed on both sides of the East African Rift System (EARS), and is a key taxon for understanding the phylogeographic patterns of divergence of the family as a whole. Phylogenetic analysis of 62 mitochondrial cyt b sequences, representing 48 distinct haplotypes from 26 geographic locations across the range of Heliophobius, consistently and robustly resolved six genetically divergent clades that we recognize as distinct evolutionary species. Early species descriptions of Heliophobius were synonymised into a monotypic taxonomy that recognized only H. argentocinereus. These synonyms constitute available names for these rediscovered cryptic lineages, for which combined morphological and genetic evidence for topotypical populations endorses the recognition of six to eight distinct taxa. Bayesian estimates of divergence times using the fossil Proheliophobius as a calibration for the molecular clock suggest that the adaptive radiation of the genus began in the early Miocene, and that cladogenesis, represented in the six extant species, reflects a strident signature of tectonic activity that forged the principal graben in the EARS.

2023, Eos, Transactions American Geophysical Union

2023, Molecular Ecology

Scattered populations of the same tree species in montane forests through Africa have led to speculations on the origins of distributions. Here, we inferred the colonization history of the Afromontane tree Prunus africana using seven chloroplast DNA loci to study 582 individuals from 32 populations sampled in a range-wide survey from across Africa, revealing 22 haplotypes. The predominant haplotype, HT1a, occurred in 13 populations of eastern and southern Africa, while a second common haplotype, HT1m, occurred in populations of western Uganda and western Africa. The high differentiation observed between populations in East Africa was unexpected, with stands in western Uganda belonging with the western African lineage. High genetic differentiation among populations revealed using ordered alleles (N ST = 0.840) compared with unordered alleles (G ST = 0.735), indicated a clear phylogeographic pattern. Bayesian coalescence modelling suggested that 'east' and 'west' African types likely split early during southward migration of the species, while further more recent splitting events occurred among populations in the East of the continent. The high genetic similarity found between western Uganda and west African populations indicates that a former Afromontane migration corridor may have existed through Equatorial Africa.

2023

The field visit was conducted at Fura and Furagosa community based wildlife conservation area in February 2021. The survey aims to prepare a primary bird checklist. Transect walk data collection method was employed. The record of bird list was presented in a descriptive statics. 37 bird species were recorded during the survey time. Of the species recorded, 25 species were residents, 10 species Palearctic migrants and 2 Intra-African migrants. The survey suggests that further systematic studies of biodiversity are needed.

2023, Molecular Ecology

2023

The Senkelle Hartebeest Animal Sanctuary is the sole protection area for the Swayne's Hartebeest, a rather rare mammal, endemic to Ethiopia. The sanctuary, entirely in Oromia borders, is near Hawassa, the Rift Valley Lakes object of growing local and international tourists and must be valorised. A link with three lakes, the Blata, via an eco-corridor to permit wildlife passage appears as its best extension. A new tech, developed in Ethiopia, could permit the rapid and diffused tree planting the corridor imposes.

2023, Tectonics

Our understanding of how magma-poor rifts accommodate strain remains limited largely due to sparse geophysical observations from these rift systems. To better understand the magma-poor rifting processes, we investigate the lithospheric structure of the Malawi Rift, a segment of the magma-poor western branch of the East African Rift System. We analyze Bouguer gravity anomalies from the World Gravity Model 2012 using the two-dimensional (2-D) radially averaged power-density spectrum technique and 2-D forward modeling to estimate the crustal and lithospheric thickness beneath the rift. We find: (1) relatively thin crust (38-40 km) beneath the northern Malawi Rift segment and relatively thick crust (41-45 km) beneath the central and southern segments; (2) thinner lithosphere beneath the surface expression of the entire rift with the thinnest lithosphere (115-125 km) occurring beneath its northern segment; and (3) an approximately E-W trending belt of thicker lithosphere (180-210 km) beneath the rift's central segment. We then use the lithospheric structure to constrain three-dimensional numerical models of lithosphereasthenosphere interactions, which indicate~3-cm/year asthenospheric upwelling beneath the thinner lithosphere. We interpret that magma-poor rifting is characterized by coupling of crust-lithospheric mantle extension beneath the rift's isolated magmatic zones and decoupling in the rift's magma-poor segments. We propose that coupled extension beneath rift's isolated magmatic zones is assisted by lithospheric weakening due to melts from asthenospheric upwelling whereas decoupled extension beneath rift's magma-poor segments is assisted by concentration of fluids possibly fed from deeper asthenospheric melt that is yet to breach the surface.

2023, Molecular Ecology

2023, Journal of Zoology

2022, Tectonophysics

The study of rift basin's morphology can provide good insights into geological features influencing the development of rift valleys and the distribution of volcanism. The Kivu rift segment represents the central section of the western branch of the East African Rift and displays morphological characteristics contrasting with other rift segments. Differences and contradictions between several structural maps of the Kivu rift make it difficult to interpret the local geodynamic setting. In the present work, we use topographic and bathymetric data to map active fault networks and study the geomorphology of the Kivu basin. This relief-based fault lineament mapping appears as a good complement for field mapping or mapping using seismic reflection profiles. Results suggest that rifting reactivated NE-SW oriented structures probably related to the Precambrian basement, creating transfer zones and influencing the location and distribution of volcanism. Both volcanic provinces, north and south of the Kivu basin, extend into Lake Kivu and are connected to each other with a series of eruptive vents along the western rift escarpment. The complex morphology of this rift basin, characterized by a double synthetic half-graben structure, might result from the combined action of normal faulting, magmatic underplating, volcanism and erosion processes.

2022, Journal of African Earth Sciences

Journal of African Earth Sciences 679 M. BOCCALETTI et al. stratigraphique et petrologique des unites souligne (1) la composition bimodale (basaltespantellerites) des unites les plus anciennes et les plus recentes et le caractere unimodal (pantellerites) des produits emis dans la periode intermediaire, (2) I'origine surtout fissurale des ignimbrites et des basaltes les plus anciens, et (3) un rapport volumique mafique/felsique de 1:5. Les donnees geologiques dans ce secteur du Rift Majeur Ethiopien suggerent qu'~ la limite Pliocene-Quaternaire, le champ de contraintes s'est modifie, passant d'une extension ~ peu pros perpendiculaire aux bords du rift ~ une extension est-ouest se traduisant par un mouvement de rift oblique. Dans ce cadre, le changement de style volcanique observe dans les zones de Nazret-Dera et d'Asela-Ziway peut 6tre lie au changement de champ de contraintes. Nous proposons un module geodynamique nouveau de I'evolution de ce secteur du Rift Majeur Ethiopien du Pliocene Superieur au R~cent. Selon ce modele, succedant ~ une premiere periode d'extension pure, un grand volume de produits rhyolitiques a et~ 6mis durant la phase de rifting oblique. Le changement de regime tectonique a favoris6 la fusion partielle de basaltes en sous-placage & la suite d'une chute de pression et d'une ~levation des isothermes.

2022, Climate-Temperature Genius Nexus

The human brains have made outstanding discoveries throughout their evolutionary history. Early innovations like fire making, tool making, taming animals, farming etc., awareness of life-threatening risks around them, and understanding of the nature of changing climates are, what outstanding discoveries made by human brains. Among millions of lives that emerged on the earth, only the ancestral lineages of humans have been awakening their brains nonstop, which lead them to the modern stages and will continue to take them onward to a targetless destiny.

2022, Antiquity

Why did humans walk upright? Previous models based on adaptations to forest or savannah are challenged here in favour of physical incentives presented by steep rugged terrain—the kind of tectonically varied landscape that has produced early hominin remains. “Scrambler man” pursued his prey up hill and down dale and in so doing became that agile, sprinting, enduring, grasping, jumping two-legged athlete that we know today.

2022, Journal of Volcanology and Geothermal Research

2022, Journal of Zoology