A characterisation of the physical properties of soil and the implications for landslide occurrence on the slopes of Mount Elgon,Eastern Uganda

Soil properties of major landslides that occurred recently on the mid-altitude slopes of Mount Elgon, eastern Uganda were analysed. A mudflow, located at the Kitati protected forest site, and two deep debris flows on the Nametsi and Buwabwala deforested steep slopes (36°–58°) were surveyed. In order to test the hypothesis that ‘soils at the landslide sites are particularly ‘problem soils’ and thus prone to landslides’, the following analyses were undertaken: particle size distribution, Atterberg limits, shear strength and factor of safety (F_s). Soils at the Kitati and Buwabwala sites exhibited expansive potential, owing to clay contents well above 20%. A clay content exceeding 32% was identified at the Nametsi debris flow site implying an extremely high expansive potential of the soil. High liquid limits (LLs) at Kitati (59%) and Buwabwala (53%) meant that the soils qualified as vertisols susceptible to landslides. High plasticity indices (PIs) (averaging 33%) also confirmed the vertic nature of soils at the Nametsi debris flow site. Whereas the value of F _s  < 1 for the Kitati site signifies an inherently unstable slope, Nametsi and Buwabwala are supposedly stable slopes (F _s  > 1). Despite this finding, the stable sites could be described as only conditionally stable because of the interplay of various physical, pedological and anthropogenic factors. The results point to the fact that soils at the landslide sites are inherently ‘problem soils’ where slope failure can occur even without human intervention. Therefore, the hypothesis that soils at three landslide sites are inherently ‘problem soils’ and prone to landslides, is accepted.     

Probabilistic seismic hazard analysis for Bangalore

This article presents the results of probabilistic seismic hazard analysis (PSHA) for Bangalore, South India. Analyses have been carried out considering the seismotectonic parameters of the region covering a radius of 350 km keeping Bangalore as the center. Seismic hazard parameter ‘b’ has been evaluated considering the available earthquake data using (1) Gutenberg–Richter (G–R) relationship and (2) Kijko and Sellevoll (1989, 1992) method utilizing extreme and complete catalogs. The ‘b’ parameter was estimated to be 0.62 to 0.98 from G–R relation and 0.87 ± 0.03 from Kijko and Sellevoll method. The results obtained are a little higher than the ‘b’ values published earlier for southern India. Further, probabilistic seismic hazard analysis for Bangalore region has been carried out considering six seismogenic sources. From the analysis, mean annual rate of exceedance and cumulative probability hazard curve for peak ground acceleration (PGA) and spectral acceleration (Sa) have been generated. The quantified hazard values in terms of the rock level peak ground acceleration (PGA) are mapped for 10% probability of exceedance in 50 years on a grid size of 0.5 km × 0.5 km. In addition, Uniform Hazard Response Spectrum (UHRS) at rock level is also developed for the 5% damping corresponding to 10% probability of exceedance in 50 years. The peak ground acceleration (PGA) value of 0.121 g obtained from the present investigation is slightly lower (but comparable) than the PGA values obtained from the deterministic seismic hazard analysis (DSHA) for the same area. However, the PGA value obtained in the current investigation is higher than PGA values reported in the global seismic hazard assessment program (GSHAP) maps of Bhatia et al. (1999) for the shield area.     

Deformation of an elastic layer coupling in different ways to a base due to a very long vertical strike-slip dislocation

The closed-form analytic expressions for the displacement and stresses at any point of an elastic layer lying over a base due to a very long vertical strike-slip dislocation are obtained. The interface between the layer and the base is assumed to be either ‘smooth-rigid’ or ‘rough-rigid’ or ‘welded’. The variations of displacement and stresses with the horizontal distance from the fault for different types of coupling of the layer with the base have been studied. It is found that the displacement for ‘welded interface’ lies between the displacements due to ‘smooth rigid’ and ‘rough-rigid’ interfaces for different positions of the observer and different values of the ratio of rigidities of the layer and half-space.     

Contesting Chinatown: Place-making and the Emergence of ‘Ethnoburbia’ in Brisbane,Australia

This paper juxtaposes the actual areas of settlement and settlement activities of Chinese migrants in Brisbane’s southern suburbs since the mid-1980s, with the concomitant, ‘government planned’ construction of the city’s Chinatown as an ‘exotic,’ ‘ethnic,’ and ‘cosmopolitan’ landmark. It argues that while the latter, as with Chinatowns in other Australian and world cities, has continued to appropriate the symbols of so-called ‘Chineseness’ to sell the locale to non-Chinese, the former, in recalling the notion of ‘ethnoburbia,’ significantly evinces actual Chinese migrants’ agency and role in place-making. In the process, these migrants have not only established a local, ethnically meaningful environment, but also challenged the still current metonymic Western image of the Chinese as preferring life in ‘ethnic’ urban enclaves that had its origin from early Chinese settlement and fundamentally detached from the lives of other ethnic groups per se. Indeed greater recognition and comprehension of such locales may go a long way to illustrate that many Chinese living in Australia today do not fit the territorial, place-based identity often associated with them in the imagination of mainstream society.     

The Gibbs energy formulation of the α, β, and γ forms of Mg2SiO4 using Grover, Getting and Kennedy's empirical relation between volume and bulk modulus

 The empirical linear relation between volume and logarithm of bulk modulus of a material, discovered by Grover, Getting and Kennedy is taken as the basis for our equation of state. Using the latest experimental information on the adiabatic bulk modulus, the equation of state is applied to the three polymorphs of Mg₂SiO₄ to develop a consistent dataset of their thermodynamic properties in the temperature range of 200–2273 K and a pressure range of 0.1 MPa–30 GPa. The results imply that the bulk sound velocity contrast (v ^β−v ^α)/v ^α increases with temperature along the α–β phase boundary and reaches the value 8.9% at 13.5 GPa, a pressure equivalent to 410 km depth in the Earth. The bulk sound velocity contrast (v ^γ−v ^β)/v ^β decreases with temperature along the β–γ phase boundary and becomes less than 0.7% at temperatures and pressures equivalent to those associated with the 520-km seismic discontinuity in the Earth. Received: 1 August 2000 / Accepted: 1 March 2001     

Ethnoscapes, entertainment and ’eritage in the global city: segmented spaces in Singapore’s Joo Chiat Road

This case study considers the early development and recent changes that have occurred in the vicinity of Joo Chiat Road, Singapore, which can be described as a ‘linear activity corridor’ linking the districts of Geylang, Katong and Marine Parade, immediately east of Singapore’s urban core. Singapore’s Urban Redevelopment Authority (URA) has declared Joo Chiat to be a ‘Conservation Area’, reflecting local-born Peranakan and Eurasian cultures, with similar status to other more central historic sites such as Chinatown, Kampong Glam, Little India and Emerald Hill. But the story of Joo Chiat has evolved along a somewhat different trajectory from the more prominent, tourism-related, heritage areas, with a multiplicity of interactions operating at the margins of the planning process. This has led to the spatial infusion of potentially discordant, globally related, ‘entertainment and recreational’ activities into an area of established urban identity and multiple attachments. When a policy of police containment was found to be inadequate in protecting local residents from undesirable impacts, changes were eventually brought about through a combination of neighbourhood activism and local political initiative. Through detailed land use inspections, press reports and strategic interviews, backed up by secondary sources, the study highlights the impingement of marginalised, potentially disruptive ‘global’ elements into a local heritage conservation area, and the importance of strong neighbourhood identity and community involvement as active components in the process of conflict resolution.     

Space operation system for Chang’E program and its capability evaluation

Space operation for China’s first lunar exploration program, Chang’E will be provided by the S-band aerospace Telemetry, Tracking and Command (TT&C) network designed for China’s manned space program. This is undoubtedly a great challenge to the ground TT&C system. The largest antennas of China’s S-band aerospace TT&C network has an aperture of only 12 m. A series of technical measures have been taken into the designing of the spacecraft-ground TT&C system to ensure that such antennas can communicate with Chang’E-1 lunar probe 400,000 km away. These include installation of high-gain directional antennae and medium-gain omni-directional antennae for the probe, adding channel encoding to the downlink channel, using both high and low data rates for information transmission and upgrade and design of ground equipment terminals. Among them, the omni-directional antenna will operate in the earth-ground transfer orbit phase and the directional antenna will operate in the lunar orbit phase. These measures satisfy the spacecraft-ground link and program design requirements. To provide accurate navigation for the probe during its Earth-Moon flight and initial lunar orbiting flight, China’s VLBI system designed for astronomical observations, will also be used besides the ranging and range rate measurement capabilities of the S-band TT&C network. The purpose is to provide 100 m accuracy in position determination during lunar orbit. This paper describes the system design, technical challenges, solutions and capability evaluation of space operation for Chang’E-1.     

Geospatial contour mapping of shear wave velocity for Mumbai city

Shear wave velocity is one of the most important input parameter in the analysis of geotechnical earthquake engineering problems, particularly to estimate site-specific amplification factor and ground response study. Dynamic in situ tests such as spectral analysis of surface waves (SASW) or multichannel analysis of surface waves (MASW) are very expensive. Also due to lack of specialized personnel, these tests are generally avoided in many soil investigation programs. Worldwide, several researchers have developed correlations between the SPT ‘N’ value and shear wave velocity ‘V _s’, which are useful for determining the dynamic soil properties. In the present study, more than 400 numbers of soil borehole data were collected from various geotechnical investigation agencies, government engineering institutes and geotechnical laboratories from different parts of Mumbai city, which is financial capital of India with highest population density. In this paper, an attempt has been made to develop the correlation between the SPT ‘N’ value and shear wave velocity ‘V _s’ for various soil profile of Mumbai city and compared with other existing correlations for different cities in India. Using Geographical Information System (GIS), a geospatial contour map of shear wave velocity profile for Mumbai city is prepared with contour intervals of 25 and 50 m/s. The scarcity of database or maps of shear wave velocity profile for Mumbai city will make the present geospatial contour maps extremely useful and beneficial to the designer, practitioners for seismic hazard study involved in geotechnical earthquake engineering.     

Ingress of Brachyuran Crab Post-larvae to the Newport River Estuary

Planktonic larvae of estuarine species often develop in the coastal ocean and return to estuaries using favorable currents. This study investigated spatial distributions of brachyuran crab post-larvae during ingress to the Newport River estuary, North Carolina, USA (34°41′ N, 76°40′ W). Nearshore plankton tows were conducted across the inlet to the estuary. Settlement on passive ‘hog’s hair’ collectors was simultaneously monitored in each of four estuarine channels. Callinectes sapidus density was highest east of the inlet, whereas relative estuarine abundance was higher in western channels. In separate sampling with collectors at coastal and estuarine locations, spatial distributions of post-larvae were consistent through time but differed for C. sapidus, Uca spp., and Pachygrapsus transversus. The diel timing of C. sapidus settlement on collectors was determined at the coast and compared to previous studies of settlement in the estuary. Behavioral responses to environmental cues may alter transport pathways from those predicted by hydrodynamic models.     

Estimation of the composition of the Earth’s primary aqueous phase. 2. Synthesis from the mantle and igneous rock material. Comparison with synthesis from the carbonaceous chondrite material

Simulation results of the equilibrium state of systems water-carbonaceous chondrite material, water-primary mantle material, water-ultramafic rock material, and water-mafic rock material open with respect to carbon dioxide and methane at 25°C, 1 bar indicate that highly alkaline reduced aqueous solutions with K/Na > 1 can be formed only if water is in equilibrium with compositions close to those of continental crust and primitive mantle. Yu.V. Natochin’s hypothesis that the living cell can be formed only in an aqueous environment with K/Na > 1 leads to the conclusion that terrestrial life could arise and further evolve on the Earth during the differentiation of primary chondritic material into the Earth’s core and mantle (during the first few million years of the planet’s lifetime) in an alkaline (pH 9–10) reduced (Eh = −400–500 mV) aqueous solution at a temperature of 50–60°C, in equilibrium with an N₂-bearing atmosphere, which also contained CH₄ (partial pressure from 10⁻² to 10⁻⁸ bar), CO₂ (partial pressure from 10⁻⁵ to 10⁻⁸ bar), NH₃, H₂, H₂S, CO, and other gases.     

Enthalpy of formation of CaSi2O5, a quenched high-pressure phase with pentacoordinate silicon

 The monoclinic titanite-like high-pressure form of calcium disilicate has been synthesized and quenched to ambient conditions to form the triclinic low-pressure phase containing silicon in four-, five- and sixfold coordination. The enthalpy of formation of the quench product has been measured by high-temperature oxide melt calorimetry. The value obtained from samples from a series of several synthesis experiments is ΔH _f = (−26.32 ± 4.27) kJ mol⁻¹ for the formation from the component oxides, or ΔH _f  = (−2482.81 ± 4.59) kJ mol⁻¹ for the formation from the elements. The result is identical within experimental error to available estimates, although the previously predicted energy difference between the monoclinic and triclinic phases could not be verified. Received: 16 February 2000 / Accepted: 14 July 2000     

A study of the bonded interactions in nitride molecules in terms of bond critical point properties and relative electronegativities

Bond critical point properties calculated for the MN bonds in a number of geometry optimized nitride molecules containing first- and second-row M cations are compared with those calculated for a number of oxide molecules. As reported for the oxides, the value of the electron density, ρ(r _c ), at the bond critical points, r _c , increases with decreasing bond length while for the more electronegative cations, the local energy density, H(r _c ) decreases nonlinearly in value as the relative electronegativities of the M-cations, χ _M , tend to increase. In the majority of cases, χ_M, |λ₁|/λ₃ and ∇²ρ(r _c ) increase with decreasing minimum energy bond lengths. The bond lengths adopted by the molecules are indicated to be an important determinant of the critical point properties of the electron density distributions. The relative electronegativities derived from the electron density distributions of the nitrides agree with those derived for the oxides and Pauling’s electronegativities to within ∼5%, on average. Received: 3 February 1997 / Revised, accepted: 11 July 1997     

Mutual replacement reactions in alkali feldspars I: microtextures and mechanisms

Intracrystal microtextures formed by a process of mutual replacement in alkali feldspars record fluid–rock reactions that have affected large volumes of the Earth’s crust. Regular, ≤1 μm-scale ‘strain-controlled’ perthitic microtextures coarsen, by up to 10³, by a dissolution–reprecipitation process, producing microporous patch or vein perthites on scales >100 μm. We have developed earlier studies of such reactions in alkali feldspar cm-scale primocrysts in layered syenites from the Klokken intrusion, South Greenland. We present new hyperspectral CL, SEM images, and laser ICPMS analytical data, and discuss the mechanism of such replacement reactions. The feldspars grew as homogeneous sodic sanidines which unmixed and ordered by volume diffusion during cooling into the microcline field at ~450°C, giving regular, fully coherent ‘braid’ cryptoperthite. At ≤450°C the crystals reacted with a circulating post-magmatic aqueous fluid. The braid perthite behaved as a single reactant ‘phase’ which was replaced by two product phases, incoherent subgrains of low albite and microcline, with micropores at their boundaries. The driving force for the reactions was coherency strain energy, which was greater than the surface energy in the subgrain mosaic. The external euhedral crystal shapes and bulk major element composition of the primocrysts were unchanged but they became largely pseudomorphs composed of subgrains usually with the ‘pericline’ and ‘adularia’ habits (dominant {110} and subordinate {010} morphology) characteristic of low T growth. The subgrains have an epitactic relationship with parent braid perthite. Individual subgrains show oscillatory zoning in CL intensity, mainly at blue wavelengths, which correlates with tetrahedral Ti. Regular zoning is sometimes truncated by irregular, discordant surfaces suggesting dissolution, followed by resumption of growth giving regular zoning. Zones can be traced through touching subgrains, of both albite and microcline, for distances up to ~500 μm. At ≤340°C, the microcline subgrains underwent a third stage of unmixing to give straight lamellar film perthites with periodicities of ~1 μm, which with further cooling became semicoherent by the development of spaced misfit dislocations. Sub-grain growth occurred in fluid films that advanced through the elastically strained braid perthite crystals, which dissolved irreversibly. Braid perthite was more soluble than the strain-free subgrain mosaics which precipitated from the supersaturated solution. Some volumes of braid texture have sharp surfaces that suggest rapid dissolution along planes with low surface energies. Others have complex, diffuse boundaries that indicate a phase of coherent lamellar straightening by volume diffusion in response to strain relief close to a slowly advancing interface. Nucleation of strain-free subgrains was the overall rate-limiting step. To minimise surface energy subgrains grew with low energy morphologies and coarsened by grain growth, in fluid films whose trace element load (reflected in the oscillatory zoning) was dictated by the competitive advance of subgrains over a range of a few tens of mm. The cross-cutting dissolution surfaces suggest influxes of fresh fluid. Removal of feldspar to give 2 vol% porosity would require a feldspar:fluid ratio of ~1:26 (by wt). The late reversion to strain-controlled exsolution in microcline subgrains is consistent with loss of fluid above 340°C following depressurization of the intrusion. A second paper (Part II) describes trace element partitioning between the albite and microcline subgrains, and discusses the potential of trace elements as a low-T geothermometer. This paper and the Part II are dedicated in memory of J.V. Smith and W.L. Brown, both of whom died in 2007, in acknowledgement of their unrivalled contributions to the study of the feldspar minerals over more than half a century.     

Post-disaster assessment of hazard mitigation for small and medium-magnitude debris flow disasters in Bali,Indonesia and Jimani,Dominican Republic

This article explores whether past exposure to debris flow disasters with a human dimension (e.g. caused in part by deforestation) results in adaptive hazard mitigation and improved environmental and resource management practices in affected areas. When guiding hazard mitigation practice, the ‘adaptive hazard mitigation’ approach views mitigation as a multi-dimensional experiment, with the associated need for post-experiment monitoring, evaluation, learning and adjustment, and attention paid to multiple scales (Bogardi 2004). This article explores how the concept of ‘adaptive hazard mitigation’ has emerged, linking this ‘adaptive management’ used increasingly in resource and environmental management. Two case studies of disasters linked to human-induced environmental change are examined, and the mitigation responses of local communities, NGOs and Government agencies are documented. Data sources include secondary data (journal articles, web-based disaster reports and grey literature) on each disaster, key informant interviews (n = 8) and direct observation over the 2005–2006 period of post-disaster mitigation actions implemented after each disaster. The research indicates that in both case studies, a limited range of hazard mitigation actions was employed, including both structural and non-structural approaches. However, the research also found that causal factors involving human-induced environmental change (e.g. deforestation) were not addressed, and overall, the hazard mitigation strategies adopted lacked monitoring, learning and adjustment. In both case studies, responses to disaster were judged to be examples of ‘trial and error’ adaptation, rather than either ‘passive’ or ‘active’ adaptation.

Auto-correlation analysis of ocean surface wind vectors

The nature of the inherent temporal variability of surface winds is analyzed by comparison of winds obtained through different measurement methods. In this work, an auto-correlation analysis of a time series data of surface winds measuredin situ by a deep water buoy in the Indian Ocean has been carried out. Hourly time series data available for 240 hours in the month of May, 1999 were subjected to an auto-correlation analysis. The analysis indicates an exponential fall of the autocorrelation in the first few hours with a decorrelation time scale of about 6 hours. For a meaningful comparison between satellite derived products andin situ data, satellite data acquired at different time intervals should be used with appropriate ‘weights’, rather than treating the data as concurrent in time. This paper presents a scheme for temporal weighting using the auto-correlation analysis. These temporal ‘weights’ can potentially improve the root mean square (rms) deviation between satellite andin situ measurements. A case study using the TRMM Microwave Imager (TMI) and Indian Ocean buoy wind speed data resulted in an improvement of about 10%.     

Structural geometry of the early Precambrian terrane south of Coimbatore in the “Palghat Gap”, southern India

The ENE-plunging macroscopic folds, traced by calc gneiss interbanded with marble and sillimanite schist within the Peninsular Gneiss around Suganapuram in the ‘Palghat gap’ in southern India, represent structures of the second generation (D₂). They have folded the axial planes of a set of D₁ isoclinal folds on stratification coaxially, so that the mesoscopic D₁ folds range from reclined in the hinge zones, through inclined to upright in the limb zones of the D₂ folds. Orthogonal relation between stratification and axial planar cleavage, and ‘M’ shaped folds on layering locate the hinge zones of the D₁ folds, whereas folds on axial planar cleavage with ‘M’ shaped folds are the sites of the D₂ fold hinges. Extreme variation in the shapes of the isoclinal D₁ folds from class 1B through class 1C to nearly class 2 of Ramsay is a consequence of buckling followed by flattening on layers of widely varying viscosity contrast. The large ENE-trending structures in this supracrustal belt within the Peninsular Gneiss in the ‘Palghat gap’ could not have evolved by reorientation of NS-trending structures of the Dharwar tectonic province to the north by movement along the Moyar-Bhavani shear zone which marks the boundary between the two provinces. This is because the Moyar and Bhavani faults are steep dipping reverse faults with dominant dip-slip component. Deceased     

A comment on: ‘TitaniQ under pressure: the effect of pressure and temperature on the solubility of Ti in quartz’, by Jay B. Thomas,E. Bruce Watson,Frank S. Spear,Philip T. Shemella,Saroj K. Nayak and Antonio Lanzirotti

Trace concentrations of Ti in quartz are used to indicate the pressure and temperature conditions of crystallization in the ‘TitaniQ’ geothermobarometer of Thomas et al. (Contrib Miner Petrol 160:743–759, 2010). It utilises the partitioning of Ti into quartz as an indicator of the pressures and/or temperatures of crystal growth. For a given value of TiO₂ activity in the system, if temperatures are inferred to ±20 °C, pressure is constrained to ±1 kbar and vice versa. There are significant contrasts, however, between the conclusions from TitaniQ and those for natural quartz (as well as other mineral phases) in volcanic rocks. Application of the TitaniQ model to quartz from the 27 ka Oruanui and 760 ka Bishop high-silica rhyolites, where the values of T, P and TiO₂ activity are constrained by other means (Fe–Ti oxide equilibria, melt inclusion entrapment pressures in gas-saturated melts, melt and amphibole compositions), yields inconsistent results. If realistic values are given to any two of these three parameters, then the value of the third is wholly unrealistic. The model yields growth temperatures at or below the granite solidus, pressures in the lower crust or upper mantle, or TiO₂ activities inconsistent with the mineralogical and chemical compositions of the magmas. CL imagery and measurements of Ti (and other elements) in quartz are of great value in showing the growth histories and changes in conditions experienced by crystals, but direct linkages to P, T conditions during crystal growth cannot be achieved.     

Sequential high-pressure transformations of FeGeO3 high-P clinopyroxene (C 2 /c) at temperatures up to 365 ¯C

 In order to elucidate high-pressure transformations of high-P clinopyroxene (C2/c) at kinetically low temperature where atoms are not thermally activated, the transformation processes of FeGeO₃ clinopyroxene (C2/c) have been investigated at pressures up to 20 GPa and 365 °C by powder X-ray diffraction using a synchrotron radiation source and TEM observation. With increasing pressure up to 20 GPa at room temperature, FeGeO₃ high-P clinopyroxene (C2/c) reversibly transforms into a new high-pressure phase, FeGeO₃(II). On increasing the temperature up to 365 °C, this phase rapidly transforms into FeGeO₃ ilmenite within about 2 h. Intensity analysis of the X-ray diffraction pattern reveals that the high-pressure phase of FeGeO₃(II) has an intermediate structure between clinopyroxene and ilmenite: the cation arrangement is similar to that of clinopyroxene and the oxygen arrangement is similar to that of ilmenite. The comparison of the crystal structures of these polymorphs suggests that clinopyroxene to FeGeO₃(II) and FeGeO₃(II) to ilmenite transformations are performed by the slight deformation of the oxygen packing and the short-range movement of cations, respectively. It is shown that this high-P clinopyroxene transforms into ilmenite through a low-activation energy path under the low-temperature condition. Received: 30 August 2000 / Accepted: 10 February 2001     

Rip current escape strategies: lessons for swimmers and coastal rescue authorities

Lagrangian flow of two rip currents was measured using human drifters to understand how variations in surf zone circulation affect exit positions of floating swimmers. Based on these results, two escape strategies were assessed, ‘do nothing’ and ‘swim parallel to the beach’. The drifter paths and exit positions were analysed to determine the best escape strategy for passive swimmers in each scenario. Of the two methods, doing nothing to allow the rip current to take a swimmer is the most effective strategy. More than 75% of rip current flow scenarios could hinder chances of escape of swimmers if the wrong direction was chosen to swim parallel to the beach to safety. This is because in many situations a swimmer encounters not only a rip current flowing offshore but also a longshore current flowing parallel to the beach. The best education campaign for the public, in addition to only swimming on a patrolled beach, would be to promote the ‘do nothing’ rip current escape strategy, as it covers all flow scenarios without reducing a swimmer’s chance of survival.     

The evolving narrative of the Darfur conflict as represented in <Emphasis Type="Italic">The New York Times</Emphasis> and <Emphasis Type="Italic">The Washington Post</Emphasis>, 2003–2009

News media influence local to global interactions between people, societies, and governments by producing place images. Representations of Africa in Western news media are heavily imbued with colonialist notions of cultural geography. In particular, Western news media have represented conflicts in Africa as ‘tribal’, a trope that erases geographic and historical context, and discourages actions that could prevent or reduce violent conflict. To determine if ‘tribalism’ remains important in coverage of African conflict, we use framing analysis to evaluate news on Sudan’s Darfur region in The New York Times and The Washington Post during 2003–2009. We find that these newspapers predictably relied on stereotypes related to tribalism to simplify Darfur’s geography and make the conflict meaningful to intended readers. Tribal portrayal of African war is inherently political, and, problematically, neither newspaper recognized that their use of the tribal narrative was parallel to the views of both the Sudanese government and external observers that challenged the actions of the Sudanese government. However, we also found that stereotypical representations became less prominent over time, apparently because reporters found that the initial, simplistic framing of the conflict did not match their encounters with geographic reality. We emphasize the decline in stereotypical tropes, because this suggests behind-the-scenes negotiation about representations in these news organizations. Recognizing voices that challenge stereotypical portrayals is necessary to developing place images that are geographically more accurate.