Recent changes in the level of Lake Abiyata, central main Ethiopian Rift

AbstractThe volcanic terrain at the western margin of the Main Ethiopian Rift in the Debre Sina area is known for its slope stability problems. This report describes research on the effects of the hydrogeological and hydrochemical dynamics on landslide triggering by using converging evidence from geological, geomorphological, geophysical, hydrogeochemical and isotopic investigations. The chemical characterization indicates that shallow to intermediate aquifers cause groundwater flow into the landslide mass, influencing long-term groundwater-level fluctuations underneath the landslide and, as a consequence, its stability. The low content of total dissolved solids and the bicarbonate types (Ca–Mg–HCO3 and Ca–HCO3) of the groundwater, and the dominantly depleted isotopic signature, indicate a fast groundwater flow regime that receives a high amount of precipitation. The main causes of the landslide are the steep slope topography and the pressure formed during precipitation, which leads to an increased weight of the loose and weathered materials. The geophysical data indicate that the area is covered by unconsolidated sediments and highly decomposed and weak volcanic rocks, which are susceptible to sliding when they get moist. The heterogeneity of the geological materials and the presence of impermeable layers embodied within the highly permeable volcanic rocks can result in the build-up of hydrostatic pressure at their interface, which can trigger landslides. Intense fracturing in the tilted basalt and ignimbrite beds can also accelerate infiltration of water, resulting to the build-up of high hydrostatic pressure causing low effective normal stress in the rock mass, giving rise to landslides.

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Geothermal activities in the Main Ethiopian Rift: Hydrogeochemical characterization of geothermal waters and geothermometry applications (Dofan-Fantale, Gergede-Sodere, Aluto-Langano)

Geothermics ◽

10.1016/j.geothermics.2013.01.001 ◽

2013 ◽

Vol 47 ◽

pp. 1-12 ◽

Cited By ~ 21

Author(s):

Madlen Pürschel ◽

Richard Gloaguen ◽

Susanne Stadler

Keyword(s):

Ethiopian Rift ◽

Geothermal Waters ◽

Main Ethiopian Rift ◽

Hydrogeochemical Characterization

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Water Quality Threats, Perceptions of Climate Change and Behavioral Responses among Farmers in the Ethiopian Rift Valley

Climate ◽

10.3390/cli9060092 ◽

2021 ◽

Vol 9 (6) ◽

pp. 92

Author(s):

Tewodros R. Godebo ◽

Marc A. Jeuland ◽

Christopher J. Paul ◽

Dagnachew L. Belachew ◽

Peter G. McCornick

Keyword(s):

Climate Change ◽

Water Quality ◽

Surface Water ◽

Water Availability ◽

Agricultural Sector ◽

Local Development ◽

Irrigated Agriculture ◽

Ethiopian Rift ◽

Adaptation Mechanism ◽

Main Ethiopian Rift

This work aims to assess water quality for irrigated agriculture, alongside perceptions and adaptations of farmers to climate change in the Main Ethiopian Rift (MER). Climate change is expected to cause a rise in temperature and variability in rainfall in the region, reducing surface water availability and raising dependence on groundwater. The study data come from surveys with 147 farmers living in the Ziway–Shala basin and water quality assessments of 162 samples from groundwater wells and surface water. Most groundwater samples were found to be unsuitable for long term agricultural use due to their high salinity and sodium adsorption ratio, which has implications for soil permeability, as well as elevated bicarbonate, boron and residual sodium carbonate concentrations. The survey data indicate that water sufficiency is a major concern for farmers that leads to frequent crop failures, especially due to erratic and insufficient rainfall. An important adaptation mechanism for farmers is the use of improved crop varieties, but major barriers to adaptation include a lack of access to irrigation water, credit or savings, appropriate seeds, and knowledge or information on weather and climate conditions. Local (development) agents are identified as vital to enhancing farmers’ knowledge of risks and solutions, and extension programs must therefore continue to promote resilience and adaptation in the area. Unfortunately, much of the MER groundwater that could be used to cope with declining viability of rainfed agriculture and surface water availability, is poor in quality. The use of saline groundwater could jeopardize the agricultural sector, and most notably commercial horticulture and floriculture activities. This study highlights the complex nexus of water quality and sufficiency challenges facing the agriculture sector in the region, and should help decision-makers to design feasible strategies for enhancing adaptation and food security.

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Fluoride enrichment mechanism and geospatial distribution in the volcanic aquifers of the Middle Awash basin, Northern Main Ethiopian Rift

Journal of African Earth Sciences ◽

10.1016/j.jafrearsci.2011.03.004 ◽

2011 ◽

Vol 60 (5) ◽

pp. 315-327 ◽

Cited By ~ 21

Author(s):

Wakgari Furi ◽

Moumtaz Razack ◽

Tamiru Alemayehu Abiye ◽

Tenalem Ayenew ◽

Dagnachew Legesse

Keyword(s):

Ethiopian Rift ◽

Main Ethiopian Rift ◽

Middle Awash ◽

Fluoride Enrichment

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Off-axis volcano-tectonic activity during continental rifting: Insights from the transversal Goba-Bonga lineament, Main Ethiopian Rift (East Africa)

Tectonophysics ◽

10.1016/j.tecto.2018.02.011 ◽

2018 ◽

Vol 728-729 ◽

pp. 75-91 ◽

Cited By ~ 9

Author(s):

Giacomo Corti ◽

Federico Sani ◽

Samuele Agostini ◽

Melody Philippon ◽

Dimitrios Sokoutis ◽

...

Keyword(s):

East Africa ◽

Tectonic Activity ◽

Ethiopian Rift ◽

Continental Rifting ◽

Main Ethiopian Rift

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Eruptive frequency of the Bora-Baricha-Tullu Moye (BBTM) volcanic system in the Central Main Ethiopian Rift

10.5194/egusphere-egu21-13966 ◽

2021 ◽

Author(s):

Amdemichael Zafu Tadesse ◽

Karen Fontijn ◽

Abate Assen Melaku ◽

Ermias Filfilu Gebru ◽

Victoria Smith ◽

...

Keyword(s):

Late Quaternary ◽

Volcanic Eruptions ◽

Volcanic Field ◽

Tectonic Activity ◽

Explosive Eruptions ◽

Ethiopian Rift ◽

Rift System ◽

Diagnostic Features ◽

Volcanic System ◽

Main Ethiopian Rift

The Main Ethiopian Rift (MER) is the northern portion of the East African Rift System and separates the Eastern and Western plateaus of Ethiopia. The recent volcanic and tectonic activity is largely focused within the rift basin along a 20 km wide zone on the rift floor. Large silicic volcanic complexes are aligned along this central rift axis but their eruptive histories are not well constrained.The Bora-Baricha-Tullu Moye (BBTM) volcanic field is situated in the central Main Ethiopian Rift and has a different appearance than the other MER volcanic systems. The BBTM constitutes several late Quaternary edifices, the major ones are: Tullu Moye, Bora and Baricha. In addition, there are multiple smaller eruptive vents (e.g. Oda and Dima), cones, and domes across the ca. 20 X 20 km wide area. Currently, there is very little information on the frequency and magnitude of past volcanic eruptions. We present a new dataset of field observations, componentry, petrography, geochronology (40Ar/39Ar), and glass major and trace element chemistry. The data are assessed as potential fingerprints to assign diagnostic features and correlate units across the area, and establish a tephrostratigraphic framework for the BBTM volcanic field.Two large-volume and presumably caldera-forming eruptions are identified, the younger of which took place at 100 ka. The volcanic products exposed in the BBTM area show that the volcanic field has undergone at least 20 explosive eruptions since then. The post-caldera eruptions have comenditic (Tullu Moye) and pantelleretic (Bora and Baricha) magma compositions. Other smaller edifices such as Oda and Dima also erupted pantelleritic magmas, and only differ slightly in composition than tephra of Bora and Baricha. Tullu Moye had two distinct explosive eruptions that dispersed tephra up to 14 km away and on to the eastern plateau. Bora and Baricha together had at least 8 explosive eruptions. Their deposits can be distinguished by their light grey color and unique lithic components. Oda had 7 eruptions, the most recent of which generated a pyroclastic density current that travelled up to 10 km away from the vent. Dima experienced at least 3 eruptions, generating tephra with a bluish-grey colour.This mapping and compositional analysis of the deposits from the BBTM in the MER indicates that the region has been more active in the last 100 ka than previously thought, which has implications for hazards assessments for the region.

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Mantle flow and orography: the effect of basal lithospheric shearing and lateral erosion gradients on continental rifting

10.5194/egusphere-egu21-1726 ◽

2021 ◽

Author(s):

Pietro Sternai

Keyword(s):

Mantle Plume ◽

Sedimentary Basins ◽

Windward Side ◽

Ethiopian Rift ◽

Mantle Flow ◽

Stream Power ◽

Main Ethiopian Rift ◽

Extensional Tectonic ◽

Continental Rifts ◽

Lateral Erosion

Mantle plume-lithosphere interactions modulated by surface processes across extensional tectonic settings give rise to outstanding topographies and sedimentary basins. However, the nature of these interactions and the mechanisms through which they control the evolution of continental rifts are still elusive. Basal lithospheric shearing due to plume-related mantle flow leads to extensional lithospheric rupturing and associated magmatism, rock exhumation, and topographic uplift away from the plume axis by a distance inversely proportional to the lithospheric elastic thickness. When moisturized air encounters a topographic barrier, it rises, decompresses, and saturates, leading to enhanced erosion on the windward side of the uplifted terrain. Orographic precipitation and asymmetric erosional unloading facilitate strain localization and lithospheric rupturing on the wetter and more eroded side of an extensional system. This simple model is validated against petro-thermo-mechanical numerical experiments where a rheologically stratified lithosphere above a mantle plume is subject to fluvial erosion proportional to stream power during extension. These findings are consistent with Eocene mantle upwelling and flood basalts in Ethiopia synchronous with distal initiation of lithospheric stretching in the Red Sea and Gulf of Aden as well as asymmetric topography and slip along extensional structures where orography sets an erosional gradient in the Main Ethiopian Rift (MER). I conclude that, although inherently related to the lithosphere rheology, the evolution of continental rifts is even more seriously conditioned by the mantle and surface dynamics than previously thoughts.

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