Rifting in east Africa and large-scale tectonic processes

Although Earth is the only known planet on which plate tectonics operates, many small- and large-scale tectonic landforms indicate that deformational processes also occur on the other rocky planets. Although the mechanisms of deformation differ on Mercury, Venus, and Mars, the surface manifestations of their tectonics are frequently very similar to those found on Earth. Furthermore, tectonic processes invoked to explain deformation on Earth before the recognition of horizontal mobility of tectonic plates remain relevant for the other rocky planets. These connections highlight the importance of drawing analogies between the rocky planets for characterizing deformation of their lithospheres and for describing, applying appropriate nomenclature, and understanding the formation of their resulting tectonic structures. Here we characterize and compare the lithospheres of the rocky planets, describe structures of interest and where we study them, provide examples of how historic views on geology are applicable to planetary tectonics, and then apply these concepts to Mercury, Venus, and Mars.

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Internal Intraseasonal Variability of the West African Monsoon in WRF

Journal of Climate ◽

10.1175/jcli-d-16-0750.1 ◽

2017 ◽

Vol 30 (15) ◽

pp. 5815-5833 ◽

Cited By ~ 2

Author(s):

Ghassan J. Alaka ◽

Eric D. Maloney

Keyword(s):

East Africa ◽

Large Scale ◽

Intraseasonal Variability ◽

West African Monsoon ◽

West African ◽

Boreal Summer ◽

Kelvin Wave ◽

The West ◽

African Monsoon ◽

External Influences

The West African monsoon (WAM) and its landmark features, which include African easterly waves (AEWs) and the African easterly jet (AEJ), exhibit significant intraseasonal variability in boreal summer. However, the degree to which this variability is modulated by external large-scale phenomena, such as the Madden–Julian oscillation (MJO), remains unclear. The Weather Research and Forecasting (WRF) Model is employed to diagnose the importance of the MJO and other external influences for the intraseasonal variability of the WAM and associated AEW energetics by removing 30–90-day signals from initial and lateral boundary conditions in sensitivity tests. The WAM produces similar intraseasonal variability in the absence of external influences, indicating that the MJO is not critical to produce WAM variability. In control and sensitivity experiments, AEW precursor signals are similar near the AEJ entrance in East Africa. For example, an eastward extension of the AEJ increases barotropic and baroclinic energy conversions in East Africa prior to a 30–90-day maximum of perturbation kinetic energy in West Africa. The WAM appears to prefer a faster oscillation when MJO forcing is removed, suggesting that the MJO may serve as a pacemaker for intraseasonal oscillations in the WAM. WRF results show that eastward propagating intraseasonal signals (e.g., Kelvin wave fronts) are responsible for this pacing, while the role of westward propagating intraseasonal signals (e.g., MJO-induced Rossby waves) appears to be limited. Mean state biases across the simulations complicate the interpretation of results.

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Spatial and temporal variation of drought patterns over East Africa

10.5194/egusphere-egu2020-6575 ◽

2020 ◽

Author(s):

Gebremedhin Gebremeskel Haile ◽

Qiuhong Tang ◽

Guoyong Leng ◽

Guoqiang Jia ◽

Jie Wang ◽

...

Keyword(s):

East Africa ◽

Large Scale ◽

Downward Trend ◽

Spatial And Temporal Variation ◽

Drought Adaptation ◽

Significant Downward Trend ◽

Drought Pattern ◽

Research Findings ◽

Negative Impacts ◽

Adaptation And Mitigation

Understanding historical patterns of changes in drought is essential for drought adaptation and mitigation. While the negative impacts of drought over east Africa have attracted increasing attention, a comprehensive and long-term spatiotemporal assessment of drought is still lacking. Here, we provided a comprehensive spatiotemporal drought pattern analysis during the period of 1964&#8211;2015 over the GHA. The Standardised Precipitation-Evapotranspiration Index (SPEI) at various timescales (1 month (SPEI-01), 3 month (SPEI-03), 6 month (SPEI-06), and 12 month (SPEI-12)) was used to investigate drought patterns on a monthly, seasonal, and interannual basis. The results showed that despite regional differences, an overall increasing tendency of the drought was observed across the GHA over the past 52 yr, with trends of change of -0.0017 yr-1, -0.0036 yr-1, -0.0031 yr-1, and -0.0023 yr-1 for SPEI-01, SPEI-03, SPEI-06, and SPEI-12, respectively. Droughts were more frequent, persistent, and intense in Sudan and Tanzania, while more severe droughts were found in Somalia, Ethiopia, and Kenya. Droughts occurred frequently before the 1990 s, and then became intermittent with large-scale impacts occurred during 1973&#8211;1974, 1984&#8211; 1985, and 2010&#8211;2011. A turning point was also detected in 1989, with the SPEI showing a statistically significant downward trend during 1964&#8211;1989 and a non-statistically significant downward trend from 1990 to 2015. Seasonally, droughts exhibited an increasing trend in winter, spring, and summer, but a decreasing trend in autumn. The research findings have significant implications for drought adaptation and mitigation strategies through identifying the hotspot regions over east Africa at various timescales. Area-specific efforts are required to alleviate environmental and societal vulnerabilities to drought events.

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Wives and daughters of early Berlin geoscientists and their work behind the scenes

Earth Sciences History ◽

10.17704/eshi.29.2.41l1rr054114q415 ◽

2010 ◽

Vol 29 (2) ◽

pp. 291-310 ◽

Cited By ~ 2

Author(s):

Barbara Mohr

Keyword(s):

Natural History ◽

East Africa ◽

Large Scale ◽

General Knowledge ◽

Type Specimens ◽

Late Nineteenth

The lives and work and accomplishments of three women, Clementine Helm Beyrich, Clara Ehrenberg and Ina von Grumbkow Reck are described. All three were writers who in the late nineteenth and early twentieth centuries significantly contributed to the field of natural history and palaeontology even though they were not academically trained. Their work included the spread of general knowledge of geosciences including technical processes among women (C. Helm), the description and drawings of new microorganisms and curation of a major micro-palaeontological collection with several thousand type specimens (C. Ehrenberg) and the maintenance of logistics for two major expeditions to Iceland and to East Africa, the latter involving large-scale excavations for dinosaurs that are still among the highlights of the Berlin Natural History Museum's exhibition today.

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East Africa infrastructure raises regional tensions

Emerald Expert Briefings ◽

10.1108/oxan-db207228 ◽

2015 ◽

Keyword(s):

East Africa ◽

Large Scale ◽

South Sudan ◽

Land Grabbing ◽

Infrastructure Projects ◽

Business Elites ◽

Content Type ◽

Northern Kenya ◽

The Past ◽

New Infrastructure

Subject Regional infrastructure ambitions. Significance Plans for large-scale regional infrastructure projects have become vehicles for economic cooperation in East Africa over the past several years. However, behind the rhetoric of regional solidarity, such ventures have become a critical arena for power rivalries to play out. Impacts Infrastructure plans are exacerbating local conflicts in northern Kenya and driving new dynamics. Land grabbing is a trend across areas where new infrastructure is meant to be, tying political and business elites to original plans. Despite its ambitions to reduce reliance on Khartoum, South Sudan is not going to be a secure infrastructure partner for some time.

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Large-scale liquefaction and fluidization in the Cap Chat Mélange, Quebec Appalachians

Canadian Journal of Earth Sciences ◽

10.1139/e98-076 ◽

1998 ◽

Vol 35 (12) ◽

pp. 1408-1422 ◽

Cited By ~ 16

Author(s):

Pierre A Cousineau

Keyword(s):

Large Scale ◽

Foreland Basin ◽

Main Mechanism ◽

Northern Limit ◽

Middle Ordovician ◽

Surrounding Matrix ◽

Tectonic Processes ◽

Lower Ordovician ◽

South Shore ◽

St Lawrence River

The Cap Chat Mélange crops out discontinuously for 200 km along the south shore of the St. Lawrence River in the Gaspé Peninsula. It is located just south of Logan's line, the northern limit of the Humber zone with the Taconian foreland basin. This mélange is composed of dismembered rocks of the adjacent formations, in particular the Lower Ordovician Rivière Ouelle and Middle Ordovician Tourelle formations, with lesser contributions by the Middle Ordovician Des Landes and the Cambrian Orignal formations. Blocks in the mélange vary in size from a few centimetres to several kilometres, with well-preserved internal stratigraphy in the larger blocks. The distribution of blocks is not uniform and the composition of the surrounding matrix changes with corresponding changes in block composition. Tectonic processes, mostly extensional and compressional faulting, are responsible for some of the chaotic aspects of the mélange. However, the main mechanism was as follows: (i) large-scale liquefaction of the mudstone-rich Rivière Ouelle Formation, (ii) sinking with consequent dismembering of the Tourelle Formation into this underlying weakened Rivière Ouelle Formation, and (iii) fluidization of the lowermost sand beds of the Tourelle Formation resulting in abundant sandstone sills and dikes in the Rivière Ouelle Formation.

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Development and Assessment of Localized Seasonal Rainfall Prediction Models: Mapping and Characterizing Rift Valley Fever Hotspot Areas in the Southern and Southeastern Ethiopia

Journal of Sustainable Development ◽

10.5539/jsd.v11n5p102 ◽

2018 ◽

Vol 11 (5) ◽

pp. 102

Author(s):

Ephrem Weledekidane

Keyword(s):

East Africa ◽

Rift Valley ◽

Rift Valley Fever ◽

Large Scale ◽

Prediction Models ◽

Rainfall Anomaly ◽

Seasonal Rainfall ◽

Valley Fever ◽

Average Rainfall ◽

Early Indicators

Rift Valley Fever disease has been recognized as being among permanent threats for the sustainability of livestock production in Ethiopia, owing to shared boarders with RVF endemic countries in East Africa. Above-normal and widespread rainfall have outweighed as immediate risk factor that facilitated historical outbreaks of the disease in the East Africa. The objective of the present study, thus, was to develop prospective localized seasonal rainfall anomaly prediction models, and assess their skills as early indicators to map high risk localized rift valley fever disease outbreak areas (hotspots) over the southern and southeastern part of Ethiopia. 21 years of daily rainfall data; for five meteorological stations, was employed in diagnosing existences of any anomalous patterns of rainfall, along with a cumulative rainfall analysis to determine if there were ideal conditions for potential flooding. The results indicated that rainfall in the region is highly variable; with non-significant trends, and attributed to be the results of the effects of large-scale climatic-teleconnection. The moderate to strong positive correlations found between the regional average rainfall and large scale teleconnection variables (r ≥ 0.48), indicated some potentials for early prediction of seasonal patterns of rainfall. Accordingly, models developed, based on the regional average rainfall and emerging developments of El Niño/Southern Oscillation and other regional climate forcings, showed maximum skills (ROC scores ≥ 0.7) and moderate reliability. Deterministically, most of the positive rainfall anomaly patterns, corresponding to El Niño years, were portrayed with some skills. The study demonstrated that localized climate prediction models are invaluable as early indicators to skillfully map climatically potential RVF hotspot areas.

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A New Conceptual Framework for Integrating Earth Observation in Large-scale Wetland Management in East Africa

Wetlands ◽

10.1007/s13157-021-01468-9 ◽

2021 ◽

Vol 41 (7) ◽

Author(s):

Stefanie Steinbach ◽

Natalie Cornish ◽

Jonas Franke ◽

Konrad Hentze ◽

Adrian Strauch ◽

...

Keyword(s):

East Africa ◽

Spatial Data ◽

Large Scale ◽

Wetland Management ◽

Sustainable Use ◽

Earth Observation ◽

Wetland Delineation ◽

Long Run ◽

Wetland Resources ◽

National Governments

AbstractWetlands are abundant across the African continent and provide a range of ecosystem services on different scales but are threatened by overuse and degradation. It is essential that national governments enable and ensure the sustainable use of wetland resources to maintain these services in the long run. As informed management decisions require reliable, up-to-date, and large coverage spatial data, we propose a modular Earth observation-based framework for the geo-localisation and characterization of wetlands in East Africa. In this study, we identify four major challenges in spatial data supported wetland management and present a framework to address them. We then apply the framework comprising Wetland Delineation, Surface Water Occurrence, Land Use/Land Cover classification and Wetland Use Intensity for the whole of Rwanda and evaluate the ability of these layers to meet the identified challenges. The layers’ spatial and temporal characteristics make them combinable and the information content, of each layer alone as well as in combination, renders them useful for different wetland management contexts.

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