Baikal Rift: Active or Passive? — Comparison of the Baikal and Kenya Rift Zones
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Keywords:
Tectonophysics
Rift zone
Rift valley
East African Rift
East African Rift
Rift valley
Rift zone
Alkali basalt
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East African Rift
Rift valley
Sedimentation
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Inland soda and saline lakes of the East African Rift Valley (EARV). This study reviews the chemical properties of inland soda-saline lakes of the EARV, classifies lake water chemical types, and assesses the spatial distribution of the major ions. The chemical data were collected from published articles (1968–2022) where the salinity (TDS) exceeded 1 g/l concentration. Based on the total alkalinity and pH, the modified formula was used to estimate the concrete proportions of CO32- and HCO3-. The lake's water chemical type was classified using (Boros and Kolpakova, 2018) classification criteria. ESRI ArcMap 10.2 GIS software was used to analyze the spatial distributions of major ions. Following the critical review of the EARV soda saline lakes the dominance of cations and anions followed the order: Na+ > K+ > Ca2+ > Mg2+ and HCO3- + CO3- > Cl- > SO42-. Tanzania had the most soda-chemical type lakes (20), followed by Ethiopia (9), Kenya (8), and Uganda (4). Soda-saline lakes were the most common in Tanzania (5). Saline lakes were mostly found in Uganda (4), Tanzania (3), and Ethiopia (1). Except for Afrera Lake in North Ethiopia and Uganda (Western Rift), the concentration of Na+, Cl-, CO3- ions, and TDS showed an increasing concentration gradient tendency from north to south in the Eastern Rift.
East African Rift
Rift valley
Alkalinity
Dominance (genetics)
Saline water
Total dissolved solids
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The present-day rift morphologies and sedimentary environments of the northern (NKR) and central (CKR) segments of the Kenya Rift are characterized by a single half-graben rift basin that hosts today Lake Turkana in the north (5° to 3°N) and a double, fully symmetric half-graben system to the south (from about 2°30'N). To the west is the Kerio half-graben, which is occupied by a single, semi-perennial fluvial system, and to the east is a complex half-graben basin that hosts the shallow freshwater Lake Baringo to the north and the saline, alkaline and organic-rich Lake Bogoria to the south. Early rifting processes in this part of the Eastern Branch of the East African Rift System started during Eocene times in the region located between 3° and 2°30'N, and resulted in the development of a set of two parallel, N-S oriented half-graben basins - the Lokichar Basin to the west; the North Kerio Basin to the east. Vertical movements along the major border faults in the NKR resulted in two long-lived lacustrine environments, Lake Lokichar to the west and the North Kerio Lake to the east. These lakes developed from Eocene under tropical climatic conditions that induced the deposition of thick high TOC shales alternating with wide fluvio-deltaic regression bodies. During the Eocene period in the CKR, sedimentation of unknown type developed into the precursors of the Kerio and Baringo-Bogoria Basins. The presence at depth of sedimentary deposits is only demonstrated by geophysical data obtained in the Kerio and Baringo Basins, and by the Kimwarer and Kamego Formations, both poorly exposed in the Kerio and Baringo Basins and which are possible relicts of early rift deposits. These basement-sourced sediments are mainly of alluvial fan and fluvial type, with brief occurrences of shallow lake environment. At the contrary of the southern NKR, abundant volcanism marked by large volumes of basaltic/ phonolitic lavas resulted in the complete filling by lavas of the whole central segment from 23 to 15 Ma. Later on, major vertical movements along the Elgeyo, Saimo and Laikipia border faults contributed to create two new half-grabens prefiguring the present-day Kerio and Baringo Basins. From early to middle Miocene, large lake bodies developed in these two basins, where they are illustrated by the Tambach and Ngorora Formations, both representative of large freshwater to saline lake environments with a good source rock potential. From about 8 Ma, rifting migrates from west to east, resulting in a single tectonically active half-graben that hosted a suite of lacustrine environments of which present-day Lakes Baringo and Bogoria are the remnants.
East African Rift
Rift valley
Half-graben
Rift zone
Paleogene
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East African Rift
Aridification
Rift valley
Tropical rain forest
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East African Rift
Rift valley
Rift zone
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All the epicenters determined in the central part of the West African Rift Valley up to the middle of 1958 have been plotted on a map. Most of them are on the faults which border the Rift; a few are on faults which crosscut it. The eastern Virunga ‘extinct’ volcanoes show a fairly strong seismic activity. The most important discovery is that of a transverse zone stretching west from Lake Kivu to the Congo River (450 km); extinct or active volcanoes are located at the intersection of this zone with the Rift Valley. Diagrams show the amount of seismic energy liberated per year within 500 km of Lwiro. The mean value is 3.5×1020 ergs/year, which is about 0.03 per cent of that of the earth as a whole.
East African Rift
Rift valley
Rift zone
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The rift valley lakes of East Africa exhibit considerable variety in size, hydrology, hydrochemistry, and sedimentary regime. Although tectonics and climate are ultimately responsible for lake formation, vol-canism may exert a significant influence upon the lake characteristics. In the Eastern Rift (Kenya, Ethiopia), extensive volcanic activity has disrupted drainage and helped create small, shallow lake basins. Weathering of volcanic rocks produces runoff waters rich in and , and smectite is a common clay mineral. In contrast, the Western Rift (Uganda, Mozambique) has localized volcanism; the lakes are large and deep with significant fluvial influents and effluents. Dissolved and are proportionately greater and detrital mineralogy is more variable. Carbonates and evaporites also reflect the hy-drochemical differences. In addition, the topographic elevation of the lake within the rift may determine the composition and rate of sedimentation.
East African Rift
Rift valley
Rift zone
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Abstract Lakes are a conspicuous feature of the eastern African Rift Valley which stretches from the Afar depression of northeastern Ethiopia through the highlands of Ethiopia, Kenya and Tanzania to southern Tanzania (29). Because no rivers flow to the ocean from the eastern African Rift Valley, the whole region is a basin of internal drainage in which lie closed-basin or endorheic lakes. Tectonic and volcanic activity associated with the formation of the Rift Valley created the lake basins. The lakes that are in the rift valley that bisects the central highlands of Kenya from Lake Magadi in the south to Lake Bogoria in the north are emphasized in this chapter (Fig. 7.1, Table 7.1).
Rift valley
East African Rift
Kenya
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