Kenya Rift Research Articles

Edifice growth and collapse of the Pliocene Mt. Kenya: Evidence of large scale debris avalanches on a high altitude glaciated volcano

The cyclic growth and destruction of the Late Cenozoic Stratovolcano Mt. Kenya have been reconstructed for its southeastern segment. At least three major debris avalanche deposits have been reconstructed and dated. The oldest deposits indicate an edifice collapse around 4.9Ma (40Ar/39Ar), followed by a larger event around 4.1Ma (40Ar/39Ar). The last and best preserved debris avalanche deposit, with still some morphological expression covering the whole 1214km2 SE sector, occurred around 2.83Ma (40Ar/39Ar). This very large debris avalanche event must have truncated the whole top of Mt. Kenya. Of the original typical hummocky relief, only local topographical depressions are still best visible and preserved. Using known geometric empirical parameters of the 3 preserved debris-avalanche deposits, the height of the sector collapse is estimated to be in the range of 5100–6500m above the current height of 1000ma.s.l. near the end lobe of the VDA deposits. This demonstrates that Mt. Kenya attained impressive altitudes during its main activity in the Pliocene, being one of the highest mountains in that time and was most probably covered by an ice cap. Correcting for the known net eastward tilting post eruptive uplift of approximately 500m of the Mt. Kenya summit, our reconstruction indicates that an at least 5.6 to 7kma.s.l. high active Mt. Kenya existed in the Pliocene landscape between 5.1 and 2.8Ma. This volcano must have significantly contributed to regional environmental change, by catching rain on its eastern slopes and projecting a rain shadow towards the Kenya Rift valley in the west. The last major edifice collapse event around 2.8Ma coincides with a major change in regional vegetation. This suggests that the truncating of Mt. Kenya may have caused significant changes in the local climate surrounding Mt. Kenya with possible implications for environmental change in the central Kenya Rift valley, the cradle of hominin evolution.

Simulating the viability of water institutions under volatile rainfall conditions – The case of the Lake Naivasha Basin

This study views the Lake Naivasha Basin in Kenya's Rift Valley as a hydro-economic system with slowly emerging basin-wide water management institutions. Possible institutions face two interlinked challenges. Firstly, large scale horticultural activities as a core economic activity in the basin require substantial and regular amounts of irrigation water, abstracted from the lake and its aquifer. The lake level and thus irrigation water availability reveal a falling trend over the last two decades, which calls for institutions aimed at restricting further expansion in water use. Secondly, the region is characterized by volatile weather conditions where periods of average and above average rainfall have alternated with prolonged droughts for centuries. That leads to highly volatile water inflows into the lake. The two challenges combined thus call for water management institutions that support sustainable water use in both the short and the long run. This study therefore investigates the effect of water institutions already existing or proposed by local stakeholder organizations on preserving target lake levels against a background of highly volatile water availability which negatively affects the economic viability of institutions. To take the absence of functioning basin-wide coordination mechanisms for water allocation into account, we employ the solution format of Multiple Optimization Problems with Equilibrium Constraints (MOPEC) in our integrated hydro-economic model. Stochastic scenario simulations with the model reveal that compliance to water regulations and thus the viability of water institutions in the Naivasha Basin would require very high penalties which are not likely to be accepted by users.

New Tortricidae (Lepidoptera) from East Africa with an account of the tortricid fauna of acacia in the Kenyan Rift Valley.

Species of Tortricidae whose larvae feed on acacia are listed, including five new species: Hystrichophora bussei Agassiz, Endotera cyaneana Agassiz, Paraeccopsis variegana Agassiz & Aarvik, Coniostola flavitinctana Agassiz & Aarvik, and C. rufitinctana Agassiz & Aarvik. Six additional species related to the aforementioned, whose life histories are not known, also are described: Paraeccopsis tanzanica Aarvik, P. addis Aarvik, P. turi Aarvik, P. botswanae Aarvik, P. pseudoinsellata Aarvik, and Coniostola laikipiana Agassiz & Aarvik. Endotera nodi Agassiz is synonymised with Endotera cyphospila (Meyrick), comb. n.; and Coniostola omistus Diakonoff is synonymised with Coniostola stereoma (Meyrick). Paraeccopsis inflicta (Meyrick) and Paraeccopsis atricapsis (Meyrick) are removed from the synonymy of Paraeccopsis insellata (Meyrick). Eucosma pharangodes Meyrick is transferred to Eucosmocydia Diakonoff. Age onychistica Diakonoff is recorded from Africa for the first time.

Trace element and Sr-Nd-Pb isotope geochemistry of Rungwe Volcanic Province, Tanzania: implications for a Superplume source for East Africa Rift magmatism

The recently discovered high, plume-like 3He/4He ratios at Rungwe Volcanic Province (RVP) in southern Tanzania, similar to those at the Main Ethiopian Rift in Ethiopia, strongly suggest that magmatism associated with continental rifting along the entire East African Rift System (EARS) has a deep mantle contribution (Hilton et al., 2011). New trace element and Sr-Nd-Pb isotopic data for high 3He/4He lavas and tephras from RVP can be explained by binary mixing relationships involving Early Proterozoic (+/- Archaean) lithospheric mantle, present beneath the southern EARS, and a volatile-rich carbonatitic plume with a limited range of compositions and best represented by recent Nyiragongo lavas from the Virunga Volcanic Province also in the Western Rift. Other lavas from the Western Rift and from the southern Kenya Rift can also be explained through mixing between the same endmember components. In contrast, lavas from the northern Kenya and Main Ethiopian rifts can be explained through variable mixing between the same mantle plume material and the Middle to Late Proterozoic lithospheric mantle, present beneath the northern EARS. Thus, we propose that the bulk of EARS magmatism is sourced from mixing among three endmember sources: Early Proterozoic (+/- Archaean) lithospheric mantle, Middle to Late Proterozoic lithospheric mantle and a volatile-rich carbonatitic plume with a limited range of compositions. We propose further that the African Superplume, a large, seismically anomalous feature originating in the lower mantle beneath southern Africa, influences magmatism throughout eastern Africa with magmatism at RVP and Main Ethiopian Rift representing two different heads of a single mantle plume source. This is consistent with a single mantle plume origin of the coupled He-Ne isotopic signatures of mantle-derived xenoliths and/or lavas from all segments of the EARS (Halldorsson et al., 2014).

An assessment of the performance of the geophysical methods as a tool for the detection of zones of potential subsidence in the area southwest of Nakuru town, Kenya

The area to the southwest of Nakuru town in Kenya located within the Kenya Rift Valley is prone to incidences of ground subsidence especially toward the end of the heavy rain season. The zones affected by subsidence are typically linear, trending approximately north–south conforming to the structural trend of the Kenya Rift Valley. These ground subsidence incidences have in the past led to collapse of houses and damage to roads that happen to be located above the affected linear zones. This study set out to investigate the potential of geophysical methods to delineate these linear zones. Two profiles of lengths 2,430 and 2,850 m, respectively, were selected for this purpose. The study was conducted immediately after one major incidence of subsidence when the zones affected were still fresh and observable. Magnetics, very low-frequency electromagnetics (VLF-EM), and gravity methods were used in the study. The choice of these methods was dictated by their widely known applicability in the detection of linear structures, especially faults. The results of the study have shown that the linear zones affected yield good response to magnetic and VLF-EM methods. Anomalies similar to those detected across fresh subsidence zones were also detected at locations where there was no surface expression of subsidence, suggesting that the latter locations are potential zones of future subsidence. Further, there were locations along the profile that were without any anomalies. The relatively low sensitivity of the zones to the gravity method is attributed to the very narrow nature of these zone and hence limited low-density material to generate appreciable negative gravity anomalies. It is concluded from this study that geophysics permits identifying the potential areas to develop surficial collapse and to identify sectors that are potentially dangerous because they present similar signatures as the sectors with surficial evidence and sectors without anomalies. The sectors without anomalies are interpreted as having a different subsoil structure to that with sinkholes.

Macroinvertebrate distributions in relation to human and animal-induced physical disturbance of the sediment surface in two Kenyan tropical Rift Valley streams

A study of macroinvertebrate distribution in relation to different levels of human and animal physical disturbance of the sediments of the Njoro (highly disturbed) and Ellegirini (less disturbed) rivers was conducted from October 2001 to June 2002, and again in 2012 only in the Njoro River. The rivers have similar climate and land-use characteristics but differ in the frequency and intensity of human and animal disturbance of their sediment surfaces. Benthic macroinvertebrates were sampled during both low discharge, when the disturbances were high, and high discharge, when the disturbances were low. Macroinvertebrate abundance and diversity were higher in the Ellegirini than in the Njoro River. Sites characterised by high disturbance had low macroinvertebrate abundance and diversity, and were dominated by one taxon that tolerated disturbance irrespective of flow regimes. A consistent decline in macroinvertebrate abundance and diversity in the Njoro River as a result of increased disturbance was evident in 2001–2002 and 2012. Macroinvertebrates are most probably redistributed via migration and dispersal, due to these physical disturbances.

Correlation of volcanic ash layers between the Early Pleistocene Acheulean sites of Isinya, Kariandusi, and Olorgesailie, Kenya

Olorgesailie, Kariandusi, and Isinya are archeological sites with Acheulean artifacts in or on the flanks of the southern Rift Valley of Kenya. 40Ar/39Ar ages on feldspar from tuffs in the Olorgesailie Formation of 992 ± 39 ka (Member 1), 974 ± 7 ka (Member 5), and 747 ± 6 ka (Member 9), 662 ± 4 ka (Member 10), and 601 ± 3 ka (Member 11) bracket most of the Acheulean sites there. A 40Ar/39 age on a tuff in the Kariandusi sequence is 977 ± 10 ka, and both sites are associated with thick diatomite deposits. No age control has been available for the site of Isinya. Electron microprobe analyses of glass from volcanic ash layers from these sites allow tephrostratigraphic correlations between them. Here we report that samples from Kariandusi below the archeological levels correlate with samples in Member 4 and Member 2 at Olorgesailie (992 ka–974 ka). Samples from a volcanic ash at Isinya above the archeological site correlate with an ash layer in Olorgesailie Member 4, showing that these artifacts are >974 ka, providing the first age control for the artifacts at Isinya. The correlation from Olorgesailie to Kariandusi shows that the diatomites at those sites were deposited at the same time ∼120 km apart but now differ in elevation by ∼700 m. Chemical similarity with obsidians from localities in the Naivasha region suggest that some of the ash layers may originate from that area.

Hypothesis: Brain size and skull shape as criteria for a new hominin family tree

Today, gorillas and chimpanzees live in tropical forests, where acid soils do not favor fossilization. It is thus widely believed that there are no fossils of chimpanzees or gorillas. However, four teeth of a 0.5-million-year (Ma)-old chimpanzee were discovered in the rift valley of Kenya (McBrearty and Jablonski, 2005), and a handful of teeth of a 10-Ma-old gorilla-like creature were found in Ethiopia (Suwa et al., 2007), close to the major sites of Homo discoveries. These discoveries indicate that chimpanzees and gorillas once shared their range with early Homo. However, the thousands of hominin fossils discovered in the past century have all been attributed to the Homo line. Thus far, our family tree looks like a bush with many dead-branches. If one admits the possibility that the australopithecines can also be the ancestors of African great apes, one can place Paranthropus on the side of gorilla ancestors and divide the remaining Australopithecus based on the brain size into the two main lines of humans and chimpanzees, thereby resulting in a coherent family tree.

Sudden flamingo deaths in Kenyan Rift Valley lakes

The East African Rift Valley Lakes Bogoria and Nakuru sometimes host around 75% of the world population of lesser flamingos Phoeniconaias minor. In this area, mysterious flamingo die‐offs have occupied researchers for four decades. Recently, cyanobacterial toxins came into the fore as a possible explanation for mass mortalities because the main food source of lesser flamingos is the cyanobacterium Arthrospira fusiformis. We took weekly samples from July 2008 to November 2009 from Lakes Nakuru and Bogoria and analyzed them by high performance liquid chromatography for microcystins. Monthly, samples were cross‐checked using protein phosphatase inhibition assays with lower detection limits and additionally screened for polar toxins. During our study period, three flamingo die‐offs occurred at L. Bogoria and we were able to analyze tissues of 20 carcasses collected at the shoreline. No cyanotoxins were detected either in plankton samples or in flamingo tissues. Accordingly, other reasons such as food composition or bird diseases played a key role in the observed flamingo die‐offs.

Building peace through social change communication: participatory video in conflict-affected communities

This paper draws on the experience of conducting participatory video in the Rift Valley of Kenya after the 2007-2008 post-election crisis, when the country underwent a period of intense ethnic violence. By linking development communication to conflict transformation theory, this article offers a framework that highlights the impact that communication for social change can have in post-conflict settings through the use of participatory media. It shows how this type of media productions can contribute to re-establishing relationships and creating a shared understanding of the conflict, while building the view of an interconnected future among opposing groups. In this case study, I illustrate how a collection of participatory videos became a peacebuilding tool for the youth in the Rift Valley. Through the information gathered from the interviews with young victims and perpetrators of the Kenya Post-election Violence, I discuss how both the filming and the screening of these films have opened a dialogue between different groups and contributed to processes of social change.

Evolution, distribution, and characteristics of rifting in southern Ethiopia

AbstractSouthern Ethiopia is a key region to understand the evolution of the East African rift system, since it is the area of interaction between the main Ethiopian rift (MER) and the Kenyan rift. However, geological data constraining rift evolution in this remote area are still relatively sparse. In this study the timing, distribution, and style of rifting in southern Ethiopia are constrained by new structural, geochronological, and geomorphological data. The border faults in the area are roughly parallel to preexisting basement fabrics and are progressively more oblique with respect to the regional Nubia–Somalia motion proceeding southward. Kinematic indicators along these faults are mainly dip slip, pointing to a progressive rotation of the computed direction of extension toward the south. Radiocarbon data indicate post 30 ka faulting at both western and eastern margins of the MER with limited axial deformation. Similarly, geomorphological data suggest recent fault activity along the western margins of the basins composing the Gofa Province and in the Chew Bahir basin. This supports that interaction between the MER and the Kenyan rift in southern Ethiopia occurs in a 200 km wide zone of ongoing deformation. Fault‐related exhumation at ~10–12 Ma in the Gofa Province, as constrained by new apatite fission track data, occurred later than the ~20 Ma basement exhumation of the Chew Bahir basin, thus pointing to a northward propagation of the Kenyan rift‐related extension in the area.

Paleohydrology of Lake Turkana and its influence on the Nile River system

The detailed paleohydrological record of Lake Turkana, the largest lake in the eastern branch of the East African Rift, is necessary for determining the connectivity between adjacent watersheds in tropical Africa. The migration of both the Intertropical Convergence Zone (ITCZ) and the Congo Air Boundary (CAB) constrains rainfall amount and duration for most of East Africa. Lake Turkana, in northern Kenya, is the world's largest desert lake and experiences two ITCZ-associated rainy seasons annually, with cumulative rainfall of ~200mm/yr. Evidence from new continuous, high-fidelity sediment core records and high-resolution CHIRP seismic reflection data suggests that Lake Turkana received enough rainfall during the African Humid Period (AHP) to fill the lake to its sill (100m above current lake level) and spilled over into the White Nile River system. An atmospheric configuration with an eastward-shifted CAB over the Turkana region and the northern Kenya Rift is invoked as an additional source of rainfall for the catchment. This configuration began abruptly at ~11ka and lasted until ~5ka when Lake Turkana became a closed basin and was cut off from the White Nile. Prior to the AHP, Lake Turkana experienced at least two desiccation events following the Last Glacial Maximum at 18.5 and 17ka when the lake was at least 100m lower than modern, as evidenced by basin-wide, high amplitude reflections and 14C-dated shallow water facies in sediment cores. Lake level fluctuations generally follow trends in mean solar insolation, however the onset of lake level extremes are much more abrupt than rates of insolation change. Lake Turkana's location in relation to atmospheric convergence and dynamic rainfall patterns makes its susceptible to extreme climate change over relatively short timescales.

The volcano–pluton interface; The Longonot (Kenya) and Kûngnât (Greenland) peralkaline complexes

An important step in studying volcanic processes is to consider the coeval processes in the subjacent magma reservoir(s). The trachytic caldera volcano Longonot (Kenya Rift Valley) and the Kûngnât syenite complex (Gardar province, Greenland) are taken to represent complementary magmatic systems, providing evidence of the volcanic and plutonic stages of evolution, respectively. The systems show many features in common; they have similar sizes, experienced two periods of caldera collapse, and were dominated by trachytic magmas, with smaller volumes of basic magma. Magmatic differentiation was dominantly by fractional crystallization of basaltic parents, with minor episodes of magma mixing and, at Kûngnât, some crustal contamination of parental basalts. A model is presented of a single, hypothetical trachytic centre, showing how evidence from one complex can be used to infer processes at the other. For example, an active convective system, with formation of wall and floor syenitic cumulates, can be inferred to exist in the Longonot magma chamber. At Kûngnât, the intermittent development of compositionally zoned caps to the magma chamber is postulated and the nature of syn-caldera eruptive activity is outlined.

PM345 Low Risk Surgery In Women Over Aged 50 Years: Is There Need For Preoperative Tests?

Introduction: Around 200,000 people were displaced from the post-election violence that occurred in Kenya in 2007 and 2008. Objectives: To assess the cardiovascular risk factors of men living in an internally displaced persons camp in Kenya. Methods: Cross sectional survey of 267 men who live in the Shalom Internally Displaced Persons Camp in the Rift Valley in Kenya. Respondent driving sampling technique was used to recruit the men. Data on cardiovascular risk factors was collected using a questionnaire (WHO STEPwise instrument) that asked about tobacco use, alcohol consumption, history of raised blood sugar. Biometric measures were taken of blood pressure, weight and height for BMI and waist hip circumference. Results: Demographic characteristics were: mean age 37 years, 84.5% were of Kikuyu ethnicity, 36% had no schooling or had not completed primary school, over half were married and the average household size was 7 people. Half were employed (predominantly in agriculture) and median monthly household income was 2500 Kenyan Shillings ($AUD 31.86). Results for cardiovascular risk factors were: 36% daily smoking, 31% consumed alcohol in past 30 days, 10% had BP 140/90 and a quarter were underweight (< 18.5 BMI). Conclusion: The overcrowded living conditions in the small mud houses in the camp are very basic with inadequate sanitation and access to fresh water. These difficult living conditions which accompany the range of cardiovascular risk factors identified among the men will lead to poor health outcomes unless the health, living conditions and access to health facilities improve. Disclosure of Interest: None Declared

Does Local Ethnic Segregation Lead to Violence?: Evidence from Kenya

When ethnic conflict is likely people seek safety in homogenous neighborhoods, but does this ethnic segregation decrease the likelihood of communal violence? This paper argues that local segregation causes violence by eroding interethnic trust. Although segregation reduces the likelihood of violent disputes between individuals, the possibility of positive interethnic contact is also lower in segregated areas. Where levels of interethnic trust are low, it is easier for political leaders and other extremists to build support for communal violence. I demonstrate that segregation increases the incidence of violence using a new dataset measuring ethnic composition and violence across approximately 700 small localities in Kenya's Rift Valley Province during Kenya's 2007/08 post-election crisis. Because segregation is likely endogenous to violence, I draw on Kenya's history of land settlement to instrument for segregation. I also demonstrate that it is unlikely that local segregation increases violence by increasing groups' organizational capacity for violence.

Tectonic structures across the East African Rift based on the source parameters of the 20 May 1990 M7.2 Sudan earthquake

Earthquakes in Kenya are common along the Kenya Rift Valley because of the slow divergent movement of the rift and hydrothermal processes in the geothermal fields. This implies slow but continuous radiation of seismic energy, which relieves stress in the subsurface rocks. On the contrary, the NW-SE trending rift/fault zones such as the Aswa-Nyangia fault zone and the Muglad-Anza-Lamu rift zone are the likely sites of major earthquakes in Kenya and the East African region. These rift/fault zones have been the sites of a number of strong earthquakes in the past such as the M w = 7.2 southern Sudan earthquake of 20 May 1990 and aftershocks of M w = 6.5 and 7.1 on 24 May 1990, the 1937 M s = 6.1 earthquake north of Lake Turkana close to the Kenya-Ethiopian border, and the 1913 M s = 6.0 Turkana earthquake, among others. Source parameters of the 20 May 1990 southern Sudan earthquake show that this earthquake consists of only one event on a fault having strike, dip, and rake of 315°, 84°, and −3°. The fault plane is characterized by a left-lateral strike slip fault mechanism. The focal depth for this earthquake is 12.1 km, seismic moment M o = 7.65 × 1019 Nm, and moment magnitude, M w = 7.19 (≅7.2). The fault rupture started 15 s earlier and lasted for 17 s along a fault plane having dimensions of ≅60 km × 40 km. The average fault dislocation is 1.1 m, and the stress drop, ∆σ, is 1.63 MPa. The distribution of historical earthquakes (M w ≥ 5) from southern Sudan through central Kenya generally shows a NW-SE alignment of epicenters. On a local scale in Kenya, the NW–SE alignment of epicenters is characterized by earthquakes of local magnitude M l ≤ 4.0, except the 1928 Subukia earthquake (M s = 6.9) in central Kenya. This NW–SE alignment of epicenters is consistent with the trend of the Aswa-Nyangia Fault Zone, from southern Sudan through central Kenya and further southwards into the Indian Ocean. We therefore conclude that the NW–SE trending rift/fault zones are sites of strong earthquakes likely to pose the greatest earthquake hazard in Kenya and the East African region in general.

Quaternary geochemical stratigraphy of the Kedong–Olorgesailie section of the southern Kenya Rift valley

This study uses a variety of geochemical parameters to reconstruct a Quaternary environmental history of the Kedong–Olorgesailie sector of the southern Kenya Rift Valley. Lacustrine, wetland and fluvial deposition took place between about 1.9 and 0.72Ma at Munyu wa Gicheru in the northern part of the study area. Sedimentation continued about 40km further south to produce the lake, wetland, fluvial and pedogenic deposits of the Olorgesailie Formation between about 1.2 and 0.5Ma. Faulting subsequently led to basin breakup at Olorgesailie and the development of Middle to Late Pleistocene cut-and-fill fluvial deposits, as well as pond, wetland and terrestrial sediments that were locally altered by pedogenesis. Tufas and calcretes also accumulated during this latter time interval.Sedimentation in these different depositional sequences reflects several long-term trends, including: 1) an increase in carbonate deposition; 2) a decrease in biogenic silica; and 3) decreased chemical weathering indices (Chemical Index of Alteration, Vogt ratios), which imply increasing Quaternary aridity and/or erosion of catchment soils. The biophile elements Br and S also increase upwards, suggesting pulses of erosion of organic soils. Plants permineralized by silica became widespread after about 0.5Ma, providing evidence that groundwater bodies were becoming silica-enriched, possibly as a result of deeper water circulation along active faults. Several fault-aligned fossil hot spring deposits with siliceous vent, pedogenic and swamp facies have been identified at Emerit in the central part of the Kedong–Olorgesailie rift. Tectonism also provided pathways for meteoric water that led to the formation of carbonate springs in the Olorgesailie area. REE patterns in clastic sediments are stable throughout the Quaternary, reflecting the dominant trachytic source rocks, but these patterns become variable in later Pleistocene calcretes and tufas documenting changing hydrochemical conditions.The geochemical evolution of the area partly reflects climate change through time. However, it also documents the influence of Quaternary rifting processes. Rift faulting affected the geochemistry of the basin sediments by 1) causing changes in the depth of fracture systems that controlled groundwater movements and sourcing of fluids, 2) changing accommodation space in which sediments could accumulate, and 3) altering relief and thus rainfall and evaporation patterns across the rift system, as well as erosion and weathering rates.

The effects of solar irradiation changes on the migration of the Congo Air Boundary and water levels of paleo-Lake Suguta, Northern Kenya Rift, during the African Humid Period (15–5 ka BP)

The water-level record from the 300m deep paleo-lake Suguta (Northern Kenya Rift) during the African Humid Period (AHP, 15–5ka BP) helps to explain decadal to centennial intensity variations in the West African Monsoon (WAM) and the Indian Summer Monsoon (ISM). This water-level record was derived from three different sources: (1) grain size variations in radiocarbon dated and reservoir corrected lacustrine sediments, (2) the altitudes and ages of paleo-shorelines within the basin, and (3) the results of hydro-balance modeling, providing important insights into the character of water level variations (abrupt or gradual) in the amplifier paleo-Lake Suguta. The results of these comprehensive analyses suggest that the AHP highstand in the Suguta Valley was the direct consequence of a northeastwards shift in the Congo Air Boundary (CAB), which was in turn caused by an enhanced atmospheric pressure gradient between East Africa and India during a northern hemisphere insolation maximum. Rapidly decreasing water levels of up to 90m over less than a hundred years are best explained by changes in solar irradiation either reducing the East African–Indian atmospheric pressure gradient and preventing the CAB from reaching the study area, or reducing the overall humidity in the atmosphere, or a combination of both these effects. In contrast, although not well documented in our record we hypothesize a gradual end of the AHP despite an abrupt change in the source of precipitation when a decreasing pressure gradient between Asia and Africa prevented the CAB from reaching the Suguta Valley. The abruptness was probably buffered by a contemporaneous change in precession producing an insolation maximum at the equator during October. Whether or not this is the case, the water-level record from the Suguta Valley demonstrates the importance of both orbitally-controlled insolation variations and short-term changes in solar irradiation as factors affecting the significant water level variations in East African rift lakes.

Electing the ‘alliance of the accused’: the success of the Jubilee Alliance in Kenya's Rift Valley

Against a history of a divided Kalenjin/Kikuyu vote and election-related violence, and a contemporary context of high levels of inter-communal mistrust and intervention by the International Criminal Court (ICC), this article explains the Jubilee Alliance's success amongst Kalenjin and Kikuyu voters in the Rift Valley in the 2013 election. To do this, it examines the pre-election context, election results in Kalenjin- and Kikuyu-dominated areas, local political debates, and election campaigns to reveal how the ‘Uhuruto’ team persuaded local residents to support this seemingly unlikely political marriage in all six elections. It is argued that the alliance used existing and emergent communal narratives of justice and competition to recast socio-economic and political debates in a way that persuaded the majority of Kalenjin and Kikuyu to support Jubilee – and to vote against Raila Odinga and the Coalition for Reform and Democracy (CORD) – as a way to protect and further their individual and collective interests. In making this argument, particular attention is given to relations between community members, and to popular support and investment in peace; negotiations between Uhuru and Ruto, and Kalenjin ‘hosts’ and Kikuyu ‘guests’; the reinterpretation of the ICC as a performance of injustice; and successful presentation of ‘Uhuruto’ as a youthful team that could bring about peace and meaningful change as compared with an old, vengeful, incumbent Odinga Odinga.

The seismicity in Kenya (East Africa) for the period 1906–2010: A review

Kenya has had a seismic station since 1963 as part of the World Wide Standardized Seismograph Network (WWSSN). In 1990, the University of Nairobi in collaboration with GeoForschungsZentrum (GFZ) started to build up a local seismological network, the Kenya National Seismic Network (KNSN), which operated for about ten years between 1993–2002. This, however, experienced a myriad of problems ranging from equipment breakdown, vandalism and lack of spares. Kenya is seismically active since the Kenya rift valley traverses through the country from north to south bisecting the country into eastern and western regions. In the central part, the Kenya rift branches to form the NW-SE trending Kavirondo (Nyanza) rift. The Kenya rift valley and the Kavirondo (Nyanza) rift are the most seismically active where earthquakes of local magnitude (Ml) in the order of ⩽2.0–5.0 occur. Furthermore, historical records show that earthquakes of magnitudes of the order of Ml⩾6.0 have occurred in Kenya. Such large magnitude earthquakes include the January 6, 1928 Subukia earthquake (Ml 7.1) and an aftershock (Ml 6.2) four days later, as well as the 1913 Turkana region earthquake (Ml 6.2). Since early 1970’s, numerous seismic investigations have been undertaken in Kenya in order to understand the formation and structure of the Kenyan part of the East African rift valley. Earthquake data from these studies is, however, rather disorganized and individual datasets, including that acquired during the period 1993–2002, cannot furnish us with comprehensive information on the seismicity of Kenya for the past ∼100years. The purpose of this paper is, therefore, to review the seismicity in Kenya for the period 1906–2010 by utilizing data and results from different sources. The general seismicity of Kenya has been evaluated using historical data, data recorded by local seismic networks, the United States Geological Survey catalogue as well as earthquake data from the numerous seismic investigations by different individuals and research groups. On the basis of earthquake data from these sources, the entire N–S trending Kenya rift valley and the NW-SE trending Nyanza (Kavirondo) rift are characterized by a high rate of seismicity, and the USGS network has been effective in detecting local M>3.0 earthquakes. A peculiar trend is exhibited by earthquakes of Ml⩾5.1 in that these occur along the N-S and NW-SE trending Kenya rift valley and the Kavirondo (Nyanza) rift zone respectively. Earthquake data from the various sources for the period 1906–2010 is complete for Ml⩾4.4 earthquakes with a b-value of 0.79 which is characteristic of tectonic active regions like rifts. There is need to revive and extend the KNSN for a greater coverage and effective seismic monitoring in Kenya.