Climate-driven variations in geothermal activity in the northern Kenya rift valley
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Keywords:
Silicic
Caldera
Rift valley
East African Rift
Geothermal exploration
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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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East African Rift
Aridification
Rift valley
Tropical rain forest
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Silicic
Caldera
Magma chamber
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Evidence for Middle-late Triassic large-scale, silicic volcanism characteristic of extensional continental terrains is widespread in the Tasman orogenic zone in eastern Australia. Detailed study of an area of SE Queensland has defined the eroded remnants of a large collapsed caldera and an associated area of rhyolite dome building and regional downsag which may be a second caldera. The silicic volcanism and minor basaltic to andesitic products have been assigned to the Aranbanga volcanic group, and the associated granite complex has been named the Mungore complex. The Mungore caldera (collapse caldera) lies on the intersection of four major structural features and is 40 km long X 25 km wide. The following products of caldera evolution can be recognized: 1) early erupted rhyolite domes; 2) ignimbrite and associated tuffs; 3) post-eruption rhyolite; and 4) Mungore complex granites. The granites can be subdivided into four types.-J.M.H.
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Silicic
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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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Gravity data from two silicic volcanic complexes, the Valles Caldera, New Mexico and the Breiddalur central volcano, Iceland, have been modelled and interpreted.
The Rubio Volcano (4 Ma to 1.5 Ma) in the area of the Toledo Embayment in the Jemez Mountains formed the centre of a depression which grew southwestwards and then collapsed to form the Toledo Caldera (1.45 Ma) and then the Valles Caldera (1.12 Ma). Published gravity data covering the Valles Caldera are used to generate three profiles across the caldera. Models in 2½D show a combination of chaotic collapse and a trapdoor caldera up to 3,600 m deep, hinged to the west with some faulted basement blocks. The maximum depth of tuffs filling the caldera are up to 1,000 m less than in previously published models, although in other places the tuffs are found to be over 1,000 m thicker.
Gravity data from Breiddalur in southeastern Iceland indicate that the partly silicic, andesitic volcano was about 2,000 m thick, with a 500 m thick silicic core and that at least two other buried silicic centres may have developed during the volcano's history.
The generation and storage of silicic magmas in these contrasting volcanic provinces is considered. Much more basic material is required at Valles than at Breiddalur to produce the inferred volumes of silicic material. The consequences of this difference are discussed.
Caldera
Silicic
Basement
Magma chamber
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