Central Rift Research Articles

Stratigraphy and eruptive history of Gedemsa caldera volcano, Central Main Ethiopian Rift

Gedemsa caldera is a peralkaline volcanic depression located in the Central sector of the Main Ethiopian Rift. An integrated volcanological study of stratigraphic sections was carried out in order to constrain the eruptive history of Gedemsa caldera volcano (GCV), Ethiopia. Textural analyses on plagioclase crystals together with field observations shed light on magma chamber processes feeding the volcanic complex. A multi-vent eruption is ascribed to the pre-caldera volcanic products, as can be seen from the varying caldera wall sequences comprising lavas and pyroclastic deposits. At least three major caldera-forming eruptions are identified producing: 1) a lower ignimbrite, 2) extensive pumice fall and pyroclastic density current deposits, and 3) an upper ignimbrite exposed in different areas of the caldera, indicating a sector collapse. We identified 20 individual pyroclastic deposits found outside and within the caldera that erupted after the climactic caldera collapse. The most recent volcanic activity at Gedemsa is characterized by rhyolitic lava domes and pyroclastic deposits from eruptions through numerous vents aligned with WNW-ESE pre-existing cross-cutting structures. Macrocryst disequilibrium textures such as fine-scale oscillatory zoning (FOZ), sieve textures, glomerocryst, and synneusis indicate that magma reservoir is characterized by repeated magma injection, convection flows, and mixing.

Effect of Land Use and Land Cover Change on Soil Erosion in Alaba Sub-Watersheds of Central Rift Valley Basin, Ethiopia

The magnitude of soil erosion rates has been accelerating in the Central Rift Valley Area of Ethiopia due to land use and land cover change (LULCC). This study aimed to analyze the trends and changes in land use and land cover dynamics and to analyze the impact of LULC change on soil erosion over the Alaba Sub-Watershed, Central Rift Valley Area of Ethiopia. This study would help to plan and use appropriate land use planning, soil, and water conservation practices, thereby reducing soil erosion in the study area. The soil loss rates were estimated using an empirical prediction model of the Revised Universal Soil Loss Equation (RUSLE) outlined in the ArcGIS environment. During the study period between 1987 and 2018, the rate of change in cultivated land and bare land was raised by 9.09% and 1.08%, respectively. On the contrary, vegetation cover and grasslands had dropped by –2.03%, and -1.42% respectively. From trends of LULC changes, cultivated land revealed an increasing trend increasing from 181.28 hectares to 351.23 hectares for the period 1987 to 2018, respectively. On the other hand, vegetation and grasslands showed a declining trend from -271.92,-22.66 hectares to -305.91, -124.63 hectares, respectively. The findings of the study generally elucidate that the LULCC has a detrimental impact on soil erosion. The estimated total annual actual soil loss in the study landscape was 25707.77 tons in 1987, 29310.71 tons in 2000, and 31769.32 tons in 2018. It was also found that the mean annual soil loss rate of the study catchment was 22.69t/ha/yr., 25.87t/ha/yr. and 28.04t/ha/yr. in 1987, 2000, and 2018 respectively. About 35% and 42% of the Sub-watershed experienced high to very severe soil erosion in 1987 and 2018, respectively. The results indicate that the estimated erosion rate for about 39 % of the sub-basin area exceeds the maximum tolerable soil erosion threshold and this shows that the erosion risk condition is deteriorating in the study landscape. The top three priority levels delineated for urgent SWC measures represent those areas within the large increase in erosion risk levels, with an area of 188 hectares and accounting for 17 % of the sub-watershed area. Therefore, further detailed investigations based on data from primary and secondary sources would be important in identifying driving socioeconomic forces and consequences of LULCCs and suggesting possible alternative options to establish sustainable resource management practices in the study area.

On-farm demonstration of improved and drought tolerant maize varieties with associated management practices

Maize is an important cereal crop in the central Rift Valley of Ethiopia. It plays a greater role in ensuring food security. The study was designed to evaluate and promote Melkassa-6Q variety with standard check (Melkassa-2). The study sites were Adama and ATJK districts. The districts were selected based on their maize production potential and accessibility of the site for demonstration. Training and field days were implemented to facilitate the successful implementation of the activity and create awareness among farmers about the varieties. Grain yield was recorded and the varieties were compared to each other based on their yield performance. Farmers ‘feedback was also collected and farmers preference ranking of each demonstrated variety was done depending on the farmers’ set criteria for variety evaluation. The mean yield of Melkassa-2 (standard check) is about 39 qt/ha across locations whereas the mean yield of Melkassa-6Q is 36.4 qt/ha which is 2.6 qt below the standard check. In addition to yield, Melkassa-2 variety was preferred over Melkassa-6Q variety in overall farmers’ evaluation criteria for maize variety evaluation. Therefore, there should be an adequate quality seed supply of Melkassa-2 variety till the best-performing maize variety is released by the research system.

Maastrichtian – Paleocene environmental and climatic conditions in Koum Basin (northern benue trough, Cameroon) inferred using a multiproxy approach including sedimentology, mineralogy, and geochemistry

The Koum Basin is one of major intracontinental basins in northern Cameroon. It is part of the Upper Benue Trough and has genetic ties to the West and Central African Rift System. The main purpose of studying the Koum Basin sedimentary deposits was to re-examine the time of the deposition and constrain the palaeoenvironmental and paleoclimatic conditions during deposition. To accomplish this, we used a combination of sedimentologic, palynologic, mineralogic, and geochemical data. Claystone units interbedded with calcareous siltstones dominate sedimentary sequence, including few clay beds, fine to medium-grained sandstone, and rare marl layers. The palynomorph assemblage suggests a previously unknown Maastrichtian – Paleocene age in this basin. The sediments originated from intermediate igneous parent rocks with a relative contribution of felsic rocks. These rocks underwent low detritism (Si/Al: 2.51–4.43; K/Al: 0.11–0.36; Ti/Al: 0.05–0.10) and chemical weathering (CIA: 55–64; PIA: 56–68) in the source region. Consequently, deposits are immature (ICV values > 1) and weakly recycled (Si2O3/Al2O3 ratios ≤5). The organic matter analysis and the palynoflora assemblage, reveal Type III kerogen with significant contributions of Type II-III and type II kerogens, as well as a continental paleo-depositional environment with open rainforest to savannah vegetation. The clay minerals distribution suggests moderate illitization and chloritization processes and thus moderate burial diagenesis at temperatures ranging from 70 to 90 °C, also attested by immature to mature Tmax values (≤436 °C) marginally. The low CIA values and very low kaolinite contents, indicate dry climatic conditions. In addition, two major-element-based discrimination diagrams show that the parent rocks of clastic sediments formed primarily in a continental arc system, with a moderate contribution from the rift system and a low contribution from the oceanic island arc, implying compressional conditions, which is consistent with previous studies on the tectonic background of the region during the late Maastrichtian to Paleocene period.

Assessment of Factors AffectingSeedling Survival in AdamiTullu andDugda District of Central Rift Valley of Oromia, Ethiopia

Assessment of Factors AffectingSeedling Survival in AdamiTullu andDugda District of Central Rift Valley of Oromia, Ethiopia

The role and interplay of institutions in water governance in the Central Rift Valley of Ethiopia

Background Institutions can play a key role in coordinating how natural resources are effectively managed and used without over-exploitation. Institutions are laws, policies, and organizational arrangements that permit, forbid or regulate human action. This study aimed to look into the roles of formal and informal institutions, and their interactions in water resources governance in the Central Rift Valley (CRV), Ethiopia. Methods Key informant interviews, focus group discussions, and secondary data sources were employed to collect relevant data. Results The result of the study indicated that the influence of informal institutions on formal institutions or vice versa was insignificant, and unable to change the actions of water users in the CRV. Other limitations observed in water resources governance in the CRV include a lack of actors’ clear roles and responsibilities, absence of meaningful decentralization, limited engagement of key actors in policy development, lack of synergy between the institutions, and absence of enforcement mechanisms. Conclusion Considering the local contexts and community’s traditional knowledge of water governance in water-related policy, rules, and regulations, and enhancing the capacity of local-level institutions, strong interplay among all institutions involved in water governance, and meaningful actors’ engagement were recommended to advance the role of institutions in water resources governance in the CRV and in the country.

Implications of large-scale agricultural investment for adaptation to climate change by smallholders in the Central Rift Valley, Ethiopia

Implications of large-scale agricultural investment for adaptation to climate change by smallholders in the Central Rift Valley, Ethiopia

Diagenesis, paleoenvironments, and petroleum geology of sediments lining the West and Central African Rift System, Koum Basin, North Cameroon

Diagenesis, paleoenvironments, and petroleum geology of sediments lining the West and Central African Rift System, Koum Basin, North Cameroon

Knowledge, attitude and participation intention to use and management of wetlands: evidence from the central rift valley of Ethiopia

Knowledge, attitude and participation intention to use and management of wetlands: evidence from the central rift valley of Ethiopia

A multi-component forager-to-herder sequence at Kapsoo Rockshelter (Chebinyiny) on the Uasin Gishu Plateau, Kenya

ABSTRACT Early archaeological investigations of the Uasin Gishu Plateau of west-central Kenya highlighted its potential importance as a geographic link between the Central Rift, the Lake Victoria Basin and the western Kenyan highlands from the Middle Stone Age to the Pastoral Neolithic and Iron Age periods. Despite this, the region has seen little focused research in recent decades. Here, we report on archaeological research at the site of Kapsoo Rockshelter, Chebinyiny Hill (GmJf1), near Moiben on the northern end of the Uasin Gishu Plateau. We combine data from original fieldwork in 1982 with renewed test excavations at Kapsoo carried out in 2022. Results of lithic, faunal and material analyses combined with radiocarbon dating reflect occupation of the northern plateau from the late Pleistocene to the late Holocene and provide the first radiometric dates for the presence of mobile herders in this region. Quantitative assessment of the rich lithic record at the site identifies significant technological change over time, providing a description of the regional Later Stone Age sequence. Finally, we present hypotheses for the relationship between Kapsoo and the nearby undated sequence at Muringa, as well as how these records fit into broader patterns of economic change across southwestern Kenya.

Making the Maasai: revisiting the history of Rift Valley Maa-speakers c.1800–c.1930

ABSTRACT This article offers a re-assessment of Maasai history from 1800 to 1930, taking a critical look at both the existing historiography and the sources on which it is based. It examines how Maasai institutions and group identities adapted to long-term environmental and social challenges, including climate change, disease, conflicts over resources and the advent of colonial overrule, always with survival as the main imperative. What emerges is a more complex and dynamic account of developments in the Central Rift Valley since the end of the eighteenth century.

Description and Evaluation of the Present Resource Use, Management Practices, and Socio-Economic Conditions in the Medo Watershed, Central Rift Valley Area of Ethiopia

Characterizing the socio-economic systems in integrated watersheds is to identify and prioritize production constraints for designing appropriate R&D interventions. The random sampling method was used to select 81 households, and both qualitative and quantitative data were collected. Formal and informal surveys were conducted to gather information about the socioeconomic and institutional issues. Descriptive statistics and diversity indices were used for data analysis. According to the results of the study, agriculture is the largest source of income in the study areas, followed by off-farm activities such as daily labor, handcraft and pension. The dominant crops grown in the watershed are maize, teff, and haricot bean, respectively. Livestock rearing is also the major means of livelihood in the study area. About 37%, 19% and 17% of the farmers owned cows, sheep and goat, respectively, in the Edo watershed. The watershed is characterized by a dynamic farming system. For instance, about 63% and 32% in the introduction of new varieties and declining in soil fertility changes over the last decade were recorded, respectively. About 58% of the households indicated that there has been a decreasing and irregularity in rainfall, while 20% of the households reacted that there is the emergence of animal and plant diseases, increasing temperature, and decrease in river flow and springs over the last 10 years in the watershed. The baseline study also identified that water erosion, deforestation, and over-tillage are the major causes of the degradation of natural resources in the watershed. In general, this study concludes that land degradation and biodiversity loss are serious concerns in the watershed. Awareness creation and strengthening capacity of rural communities on integrating crops, livestock, and natural resource management technologies for effective soil and water conservation measures should be enhanced for sustainable livelihood improvement.

The development of rifting and magmatism in the multiply rifted Turkana Depression, East Africa: Evidence from surface-wave analysis of crustal and uppermost mantle structure

The Turkana Depression separates the uplifted Ethiopian and East African Plateaus. It was the site, in Mesozoic times, of a failed episode of NE–SW-oriented rifting (the Anza Rift), but now hosts E–W-oriented Nubia–Somalia separation at the junction between the Main Ethiopian Rift in the north and the Eastern Rift to the south. However, the time-integrated effect of these rifting phases on crustal and lithospheric mantle architecture and thermal structure is poorly understood. Utilising data from new seismograph networks in the Turkana Depression and northern Tanzania Craton, we produce a detailed anisotropic crustal and uppermost mantle shear-wave velocity model of the region. Within the Tanzania Craton, slightly lower uppermost mantle wavespeeds (4.4–4.5 km/s) compared to neighbouring regions, and coincident rift-parallel crustal anisotropy, imply the Nyanza Rift developed in relatively weak mobile belt lithosphere between two refractory Archean blocks. At upper-crustal (≲10 km) depths in the Turkana Depression, the slowest velocities (≲3.2 km/s) are attributed to thick Mesozoic-age sedimentary basins. Nowhere within the Depression is the mid-to-lower crust or lithospheric mantle associated with wavespeeds as slow, or seismic anisotropy as strong, as that observed below the melt-rich central and northern Main Ethiopian Rift (MER) and Ethiopian Plateau further north. High upper mantle wavespeeds (≳4.5 km/s), coinciding with the broadening of MER-rifting into southern Ethiopia, confirm the presence of refractory Proterozoic lithosphere acting as a rheological boundary to rift development. Thinned crustal zones associated with failed Mesozoic Anza rifting are also underlain by fast wavespeed (>4.5 km/s) mantle lithosphere, implying this area has resisted significant thermomechanical modification from Miocene-Recent extension and magmatism. Pre-existing crustal thin zones do not, therefore, necessarily represent zones of plate-weakness where subsequent phases of rifting will develop.

Deepest known novel species of the genus Ophiuroglypha Hertz, 1927 (Echinodermata: Ophiuroidea) from the central rift zone, Philippine Sea

A new species of brittle star was collected in 2021 by the manned submersible “Fendouzhe” from the central rift zone deep waters, Philippine Sea, at a depth of 7729 m. It is described as Ophiuroglypha fendouzhe sp. nov., and is distinguished from its congeners based on the following features: slender arms, separated dorsal and ventral arm plates, overlapping large disc scales, and distally contiguous radial shields. We provide comprehensive descriptions of the external morphological features, including characteristics of the arm skeleton, and a phylogenetic analysis based on COI sequences. The interspecific genetic distance variation in the genus Ophiuroglypha found in this study was 3.89% to 24.25%. The new species constitutes the deepest known record for the genus Ophiuroglypha.

Geophysical Based Groundwater Potential Zone Mapping: Perspectives and Inferences from Lisana Area along the Guder River, Western Margin of the Central Main Ethiopian Rift

Vertical electrical soundings and magnetic data were used to map the groundwater aquifer system in the Lisana area along the Guder River, northeast of Hosanna town, near the western margin of the Central Main Ethiopian Rift. The surveys were used to map a potential aquifer zone and investigate the groundwater potential for the current and future development of the resource in the Lisana area. The VES data were used to map the depth of a potential aquifer zone and its distribution over the area. The magnetic survey was used to delineate contacts between lithologic units and geological structures. Two-dimensional magnetic forward modeling and one-dimensional electrical modeling were used to identify fractures and lithological units containing potential groundwater. The magnetic and electrical resistivity modeling indicated that a potential aquifer occurs at a depth range from 115m to 142m. The potential aquifer occurs within weathered and fractured ignimbrite and a pumice layer containing sandy soil. This latter lithological unit is the main water-bearing horizon.

Statistical Analysis of Seismicity in the Horn of Africa

The Horn of Africa is considered as one of the seismically active regions on the African continent because of the Main Ethiopian rift system, one of the most active rift systems within the East African rift system. Therefore, it is essential to continuously analyze the seismicity to assess seismic hazards in a region of interest. To this end, seismicity information for the Horn of Africa was collected from ISC catalogues from the year 1973 to 2022 in the latitude range of 0N - 20N and the longitude range of 30E -52E from the surface to 700km below the surface. Then, as a measure of the seismicity in the Horn, Gutenberg's parameters and the spatial variation of the seismic moment were examined. According to the findings, the North Main Ethiopian Rift (NMER) is under more stress than the Central Main Ethiopian Rift (CMER) regarding seismic moment release. The Richter and Guttenberg's constants of a=6.85, b=0.88 and Mc=4.5 were obtained across the whole Horn of Africa, whereas the corresponding values for NMER, CMER and SMER were a=5.6, b=0.78, Mc=4.5; a=5.9, b=0.87, Mc=4.5; and a=6.9, b=1.03, Mc=5.0 respectively. Overall, the distribution of focal depths and magnitude showed that the distribution of seismicity in the Horn of Africa is shallow with an average focal depth of around 11 km.

Project Management Practices and Implementation of Donor Funded Water and Sanitation Projects in Central Rift Region, Kenya

The general objective of this study was to establish the influence of project management practices on implementation of donor funded water and sanitation projects in the Central Rift region, Kenya. The study specifically sought to establish the influence of stakeholder involvement, project team training, monitoring and evaluation and risk management on implementation of donor funded water and sanitation projects in the Central Rift region, Kenya. The study was anchored on four theories, namely; stakeholder theory, team theory, dynamic capabilities theory and the theory of resilience. For purposes of this study, a descriptive survey design was employed. The target population were all 160 project members comprising project managers, consultants, project implementation teams and task managers from donor agencies in 16 donor funded water and sanitation projects in the central rift region. Using statistical formulae, a sample of 62 elements was obtained. Purposive sampling was then used in targeting the said staff in each of the donor funded water and sanitation projects. This study used questionnaires in collecting data from the target group. Pilot-test was conducted to check the reliability of the instruments used for data collection. Data was analyzed using both descriptive and inferential statistics with the aid of the Statistical Package for Social Sciences (SPSS) version 25.0. The study revealed that when all the variables for project management practices, stakeholder involvement, project team training, project evaluation and risk management, were multi regressed against the dependent variable, project implementation, there was an observable model of good fit at 99.6% hence, a good predicator of project implementation if cumulatively practiced. The study further found that stakeholder involvement is a significant predicator (p=0.046<.05) of project implementation in donor funded water and sanitation projects in the Central Rift region, Kenya. Further, the study established that project team training is an insignificant positive predicator (p=0.800 >.05) of project implementation. Project evaluation is a significant predictor (p=0.024<.05) of project implementation and role risk management was found to be a significant predictor (p= 0.21 <05) project implementation. Regression analysis revealed that risk management variable (β = 7.633) has the greatest influence, followed by stakeholder engagement variable (β = 1.192) then followed by evaluation variable (β = 0.116) and lastly project team training variable (β = -0.672).Therefore, the study recommended that, project implementation teams for donor funded water and sanitation projects in Kenya should emphasize more on project risk management as it has the most significant influence on project implementation. The study recommends that the donors of the water projects should sustain, project team training, as much it does not significantly influence project implementation, but it contributes significantly to the overall model fit. The findings of this study will be significant to the government since it aims to stimulate economic growth through attaining value for money for funds sourced from donors. The study will also provide opportunities for project managers to identify key project management practices and how they influence implementation of donor funded water and sanitation projects.

Variscan structural evolution and metallogenic implications at the paleozoic maider basin, eastern anti-atlas, Morocco

In the Moroccan eastern Anti-Atlas, the Paleozoic Maider basin, hosts a range of economic mineral deposits, including Cu, Pb, Fe, and barite forming an important mineralized vein system. In this study, detailed mapping of fractures and veins, structural analysis, and measurements have been integrated to understand the structural control, the tectonic evolution, and fault kinematic history in the Paleozoic outcrops of the Southern margin of the Maider basin. The structural analysis shows two folding phases: (i) a first phase, which generates WNW-ESE-trending folds, in response to an NNE-SSW compression, likely, of Late Westphalian age. And (ii) a second phase which develops N–S metric folds, under a NE-SW to E-W compression, compatible with the Late Variscan shortening, known in the East Anti-Atlas and the Ougarta belt during the Stephano-Autunian period. Moreover, three main fault systems were distinguished: WNW-ESE to E-W, NE-SW and scarcely N–S. These fault systems record evidence of a previous extensional tectonic event that probably corresponds to the Devonian extensional event. During the late Variscan shortening, these faults were reactivated into a left-lateral strike-slip movement with a small reverse component for the WNW-ESE to E-W faults, and right lateral strike-slip motion for NE-SW ones. The mineralization primarily takes place within a vein-type system, which is predominantly found in a network of faults oriented between N30 and N60. These ore bodies present frequently lenticular and banded geometries, and do not show any evidence of deformation, suggesting probably a post Variscan emplacement age. Thus, we could link the mineralization emplacement to the Triasic Central Atlantic rifting.

Mapping Community Perception, Synergy, and Trade-Off of Multiple Water Values in the Central Rift Valley Water System of Ethiopia

Individuals and communities use and value water in multiple and complex ways. In Sub-Saharan Africa (SSA), the pluralistic nature of water values is poorly documented, and the existing and potential value trade-offs are unidentified. This study was undertaken in the Central Rift Valley (CRV) of Ethiopia to understand and map water values, priorities, risks, and trade-offs in a multi-stakeholder engagement process to provide the basis for more transparent and accountable decision-making. Integrated assessment methods, combining bio-physical and social methods, were applied. The results show 24 community-perceived and articulated water values that are diverse but interconnected, including values of water, landscapes, the river system, and downstream water bodies. Connections between people and landscape structures are articulated. In terms of priority water values, the overall results reflect the primary but basic need for water for food security and domestic uses. The results further illustrate the pluralistic nature of water values and the dichotomy of preferences among people of different backgrounds. The scenario-based Environmental Flow (EF) assessment exercise integrated into community value preferences and the event calendar that was used show that the river systems in CRV (Ketar, Kulumsa, and Gusha-Temela) have different ecological and socio-cultural flow requirements and that there are marked water value trade-offs. The conclusions of the study suggest that overlapping governance structures are affecting people’s perceptions of water and the way they articulate water values. Policy directions and decision-making need to recognize and acknowledge the multiple water values and competing uses of water in the CRV as a starting point to reconcile trade-offs that will then improve water security. Findings suggest that EF estimation and decision support tools can be customized to local ecological requirements through engaging local stakeholders in the assessment process.

Sugarcane Yield and Juice Quality as Affected by Harvest Age and Chemical Ripeners in Central Rift Valley of Ethiopia

Sugarcane Yield and Juice Quality as Affected by Harvest Age and Chemical Ripeners in Central Rift Valley of Ethiopia