THE DEVELOPMENT OF CONTINENTAL MARGINS IN PLATE TECTONIC THEORY

1974 ◽  
Vol 14 (1) ◽  
pp. 95 ◽  
Author(s):  
David A. Falvey
Keyword(s):  
Cross Sections ◽  
Large Scale ◽  
Boundary Migration ◽  
Continental Margins ◽  
Plate Tectonic ◽  
East African ◽  
Sequence Of Events ◽  
Red Sea Rift ◽  
Lithospheric Plates ◽  
African Rift

Atlantic-type continental margins are formed by rifting and subsequent breakup of continents by sea-floor spreading. Large scale horizontal displacements of continental blocks on lithospheric plates are well-described by current plate tectonic theory. However, the rifting process itself entails vertical tectonics which operate prior to breakup, and such processes are not well understood within the framework of plate tectonic theory.The qualitative models, at present described in the literature involve a sequence of events illustrated by type examples: the East African Rift; the ethiopian-Afar Rift; the Red Sea Rift; and the Gulf of Aden. The thinning and subsidence of the continental crust during rifting have been considered to be the result of crustal stretching. However the writer considers the evidence ambiguous and the theory inadequate. The model presented here involves the response of the crust and the lithosphere to thermal processes implicit in plate tectonic theory. Firstly, uplift is caused by thermal expansion and phase-boundary migration in the lithosphere. which leads to crustal thinning by erosion. Secondly, subsidence is caused by metamorphism in the deep crust. These events occur out of phase and result in two cycles of uplift/erosion/and subsidence during continental margin formation.From this generalised model, theoretical time-stratigraphic and structural cross sections may be constructed to suit the different continental margins. These cross sections are composed of different litho-tectonic elements, namely: pre-rift, rift valley, and post breakup, which are in general separated by two angular unconformities. These features may be readily identified on Atlantic continental margins with only a minimum of seismic and well control.

scholarly journals Large-Scale Atmospheric Dispersal Simulations Identify Likely Airborne Incursion Routes of Wheat Stem Rust Into Ethiopia

2017 ◽  
Vol 107 (10) ◽  
pp. 1175-1186 ◽  
Author(s):  
M. Meyer ◽  
L. Burgin ◽  
M. C. Hort ◽  
D. P. Hodson ◽  
C. A. Gilligan
Keyword(s):  
Stem Rust ◽  
Large Scale ◽  
Dispersion Model ◽  
Fungal Spores ◽  
Disease Outbreaks ◽  
Particle Dispersion ◽  
East African ◽  
Wheat Stem Rust ◽  
Sub Saharan ◽  
African Rift

In recent years, severe wheat stem rust epidemics hit Ethiopia, sub-Saharan Africa’s largest wheat-producing country. These were caused by race TKTTF (Digalu race) of the pathogen Puccinia graminis f. sp. tritici, which, in Ethiopia, was first detected at the beginning of August 2012. We use the incursion of this new pathogen race as a case study to determine likely airborne origins of fungal spores on regional and continental scales by means of a Lagrangian particle dispersion model (LPDM). Two different techniques, LPDM simulations forward and backward in time, are compared. The effects of release altitudes in time-backward simulations and P. graminis f. sp. tritici urediniospore viability functions in time-forward simulations are analyzed. Results suggest Yemen as the most likely origin but, also, point to other possible sources in the Middle East and the East African Rift Valley. This is plausible in light of available field surveys and phylogenetic data on TKTTF isolates from Ethiopia and other countries. Independent of the case involving TKTTF, we assess long-term dispersal trends (>10 years) to obtain quantitative estimates of the risk of exotic P. graminis f. sp. tritici spore transport (of any race) into Ethiopia for different ‘what-if’ scenarios of disease outbreaks in potential source countries in different months of the wheat season.

Sentinel-1 InSAR data by LiCSAR system

2021 ◽  
Author(s):  
Milan Lazecky ◽  
Yasser Maghsoudi Mehrani ◽  
Scott Watson ◽  
Yu Morishita ◽  
John Elliott ◽  
...  
Keyword(s):  
Time Series ◽  
Large Scale ◽  
Atmospheric Correction ◽  
East African ◽  
Digital Elevation ◽  
African Rift ◽  
Earth Observation Satellites ◽  
Elevation Model ◽  
Data Coherence ◽  
Standard Frame

<p>Looking Into the Continents from Space with Synthetic Aperture Radar (LiCSAR) is a system built for large-scale interferometric processing of Sentinel-1 data. LiCSAR automatically produces geocoded wrapped and unwrapped interferograms combining every acquisition epoch with four preceding epochs, and complementary data (coherence, amplitude, line-of-sight unit vectors, digital elevation model, metadata, and atmospheric phase screen estimates by the Generic Atmospheric Correction Online Service, GACOS).</p><p>The LiCSAR products are generated in frame units where a standard frame covers ~220x250 km, at 0.001° resolution (WGS-84 coordinate system). Frames are continuously updated for tectonic and volcanic priority areas. In 2020, the LiCSAR system covered about 1,500 global frames in which we have processed over 89,000 Sentinel-1 acquisitions and generated over 300,000 interferograms. Among these, 470 frames cover 1,024 global volcanoes. We aim to cover the global seismic mask defined by the Committee on Earth Observation Satellites (CEOS), but focus initially on the Alpine-Himalayan belt and East African Rift.</p><p>We serve the products as open and freely accessible through our web portal: https://comet.nerc.ac.uk/comet-lics-portal and aim to provide them to shared infrastructures as the European Plate Observing System (EPOS). We also generate rapid response coseismic interferograms for earthquakes with moment magnitude (Mw)> 5.5  a few hours after the postseismic data become available, and we update frames covering active volcanoes twice per day.</p><p>Our products can be directly converted to displacement time series and velocities using  the LiCSBAS time series analysis software. We present solutions implemented in LiCSAR, and show several case studies that use LiCSAR and LiCSBAS products to measure tectonic and volcanic deformation.</p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.1c122b867cff59390830161/sdaolpUECMynit/12UGE&app=m&a=0&c=02895a62108de9393057db6a355e3b06&ct=x&pn=gnp.elif&d=1" alt=""></p>

Carbonatite-melilitite association in the Italian collision zone and the Ugandan rifted craton: significant common factors

2000 ◽  
Vol 64 (4) ◽  
pp. 675-682 ◽  
Author(s):  
D. K. Bailey ◽  
J. D. Collier
Keyword(s):  
Large Scale ◽  
Common Factor ◽  
Distribution Patterns ◽  
Similar Distribution ◽  
East African ◽  
Type Area ◽  
Igneous Province ◽  
African Rift ◽  
The Many ◽  
Province Level

AbstractItalian carbonatites form part of a suite with melilitites, normally an association characteristic of continental interiors; the perfect analogue of the Italian suite being the kamafugites (from the type area in SW Uganda, where the western branch of the East African Rift Zone cuts across the craton). The latter are commonly attributed to plume generation, whereas the Italian carbonatites, strung along the Appennine front, are usually linked to subduction. Evidently these two mechanisms are not essential, since neither can apply in both provinces. This conclusion is re-inforced by the related magmatism registered in both provinces in the Cretaceous. Phlogopite is ubiquitous in the mantle debris, and compositions from the two provinces overlap. Xenolithic phlogopites are distinct from cognate micas in the lavas, and from the carrier melt compositions, with similar distribution patterns in both suites. Kamafugitic magmas must be products of exceptional conditions, and added to the many near-identical magmatic features, the Italian and Ugandan volcanoes have sampled similar mantle conditions. Although the large scale geodynamic regimes are in total contrast, as are the deep mantle tomographic structures, the crucial common factor at the igneous province level is extensional tectonics. Extension, promoting release of volatiles (esp. CO2), is the vital trigger for this small volume, primary magmatism.

TECTONOMAGMATIC EVOLUTION OF THE EAST AFRICAN RIFT SYSTEM AS DOCUMENTED IN WEST TURKANA, KENYA

2017 ◽  
Author(s):  
Sara Mana ◽  
◽  
Merry Yue Cai ◽  
Catherine C. Beck ◽  
Steven L. Goldstein
Keyword(s):  
East African Rift ◽  
Rift System ◽  
East African Rift System ◽  
East African ◽  
African Rift

FEEDBACK BETWEEN STRUCTURAL INHERITANCE, MAGMA-PLUMBING AND FAULTING IN A MULTIPHASE RIFT: THE SHIRE GRABEN, EAST AFRICAN RIFT

2019 ◽  
Author(s):  
Travis J. Vick ◽  
◽  
Folarin Kolawole ◽  
Estella A. Atekwana ◽  
Daniel Lao-Davila ◽  
...  
Keyword(s):  
East African Rift ◽  
East African ◽  
Structural Inheritance ◽  
African Rift ◽  
Magma Plumbing

PLIO-PLEISTOCENE PALEOENVIRONMENTS IN WEST TURKANA (EAST AFRICAN RIFT SYSTEM, KENYA)

2020 ◽  
Author(s):  
Alexis Nutz ◽  
◽  
Mathieu Schuster ◽  
Doris Barboni ◽  
Ghislain Gassier ◽  
...  
Keyword(s):  
East African Rift ◽  
Rift System ◽  
East African Rift System ◽  
East African ◽  
African Rift

scholarly journals Diversification of the Balloon bushcrickets (Orthoptera, Hexacentrinae, Aerotegmina) in the East African mountains

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Beata Grzywacz ◽  
Elżbieta Warchałowska-Śliwa ◽  
Maciej Kociński ◽  
Klaus-Gerhard Heller ◽  
Claudia Hemp
Keyword(s):  
Molecular Phylogeny ◽  
Large Scale ◽  
Diploid Number ◽  
Karyotype Analysis ◽  
Spatial Separation ◽  
Eastern Arc Mountains ◽  
East African ◽  
Habitat Islands ◽  
Extinction Event ◽  
Underlying Processes

AbstractEast African mountains constitute a network of isolated habitat islands among dry savannah and are thus ideal for studying species diversification processes. This study elucidated the phylogenetic and phylogeographic relationships of all bushcricket species comprising the genus Aerotegmina. Our analysis indicated that large-scale climatic and topographic processes in Africa are likely to have driven speciation in this group, and revealed the cytogenetic traits of the species. Molecular phylogeny supported the monophyly of Aerotegmina and showed that the genus probably originated in the old Eastern Arc Mountains of Tanzania and Kenya. Two lineages were distinguished: small- and large-sized species with geographically distinct habitats. The underlying processes are thought to be eight dispersals, ten vicariance events, and one extinction event linked to repeated fragmentation of the African rainforest. Those processes, in conjunction with habitat change, probably also led to the spatial separation of the species into a northern clade with a diploid number of chromosomes 2n = 32 + X0 or 2n = 30 + neo-XY and a southern clade with a reduced number of chromosomes (2n = 28 + X0 or 24 + neo-X1X2Y). Karyotype analysis suggests that Aerotegmina is currently in the process of speciation.

Sign in / Sign up

Export Citation Format

Share Document