scholarly journals Hazard potential of volcanic flank collapses raised by new megatsunami evidence

2015 ◽  
Vol 1 (9) ◽  
pp. e1500456 ◽  
Author(s):  
Ricardo S. Ramalho ◽  
Gisela Winckler ◽  
José Madeira ◽  
George R. Helffrich ◽  
Ana Hipólito ◽  
...  
Keyword(s):  
Large Scale ◽  
Cape Verde ◽  
Volume Flux ◽  
Cape Verde Islands ◽  
The Real ◽  
Hazard Potential ◽  
Volcanic Islands ◽  
Run Up ◽  
Santiago Island ◽  
The Impact

Large-scale gravitational flank collapses of steep volcanic islands are hypothetically capable of triggering megatsunamis with highly catastrophic effects. Yet, evidence for the generation and impact of collapse-triggered megatsunamis and their high run-ups remains scarce or is highly controversial. Therefore, doubts remain on whether island flank failures truly generate enough volume flux to trigger giant tsunamis, leading to diverging opinions concerning the real hazard potential of such collapses. We show that one of the most prominent oceanic volcanoes on Earth—Fogo, in the Cape Verde Islands—catastrophically collapsed and triggered a megatsunami with devastating effects ~73,000 years ago. Our deductions are based on the recent discovery and cosmogenic3He dating of tsunamigenic deposits found on nearby Santiago Island, which attest to the impact of this giant tsunami and document wave run-up heights exceeding 270 m. The evidence reported here implies that Fogo’s flank failure involved at least one fast and voluminous event that led to a giant tsunami, in contrast to what has been suggested before. Our observations therefore further demonstrate that flank collapses may indeed catastrophically happen and are capable of triggering tsunamis of enormous height and energy, adding to their hazard potential.

Statement by the Frelimo Executive Committee on the Events in Portugal

1974 ◽  
Vol 4 (2) ◽  
pp. 58-59
Keyword(s):  
Armed Forces ◽  
Well Being ◽  
Cape Verde ◽  
National Liberation ◽  
Cape Verde Islands ◽  
Coup D'etat ◽  
Guinea Bissau ◽  
National Salvation ◽  
The Government ◽  
The Impact

On 25 April 1974, we learned from radio broadcasts about the coup d'etat in Portugal by the armed forces which resulted in the ousting of the government of Marcelo Caetano and its replacement by a Junta of National Salvation. This movement, according to its promoters, is intended to provide a solution to the present crisis which the Portuguese regime and society are going through after thirteen years of colonial war.The coup d'etat which has just taken place cannot be seen in isolation. It is a result of the new awareness of growing sectors of the Portuguese people that the purpose of the colonial war launched by the fascist regime is to suppress the colonized peoples’ aspiration to independence and freedom and is against the desire for well-being and political and social democracy of the Portuguese people themselves.At this time we hail, in the first place, the Portuguese democratic forces which for many years have been actively and courageously opposing the colonial wars. This growing awareness is closely bound up with the affirmation of the unshakable will of the Mozambjcan people, and of the peoples of Angola, Guinea-Bissau and the Cape Verde islands, to achieve independence and freedom. This will has taken on material form in the armed struggle for national liberation which has been steadily growing and has already reached vital regions of our country. The coincidence between the crisis of the regime in Portugal and the great advances of the national liberation struggle in Mozambique over the past two years is no accident, but additional proof of the impact of our struggle on the situation in Portugal. The determinant factor of the situation in Portugal and the colonies has been and still is the struggle of our peoples. And the fundamental issue upon which the solution of all other problems depends is the independence of the peoples of Mozambique, Angola and Guinea-Bissau and the Cape Verde islands, as well as that of the remaining Portuguese colonies.

Charles Darwin in the Cape Verde and Galápagos archipelagos: The role of serendipity in development of theories on the ups and downs of oceanic islands

2015 ◽  
Vol 34 (2) ◽  
pp. 220-242 ◽  
Author(s):  
Markes E. Johnson ◽  
B. Gudveig Baarli
Keyword(s):  
Charles Darwin ◽  
Galapagos Islands ◽  
Oceanic Islands ◽  
Cape Verde ◽  
Galápagos Islands ◽  
Cape Verde Islands ◽  
Upward Growth ◽  
Volcanic Islands ◽  
The Look ◽  
St Helena

The 1831–1836 voyage of H.M.S. Beagle under Captain Robert FitzRoy launched Charles Darwin's entry into the world of geology with two pioneering publications on oceanic islands to his credit. Best known is Darwin's 1842 contribution on the theory of atoll development from the subsidence of volcanic islands and coeval upward growth of coral reefs. This work can be linked, in part, to the ten days during which the Beagle visited the Keeling (Cocos) Islands. The subsequent and lesser known of Darwin's parallel contributions is his 1844 summary on all the volcanic islands visited during the expedition, including Santiago (Cape Verde Islands), Terceira (Azores), St. Paul's Rocks, Fernando Noronha, Ascension, St. Helena, the Galápagos Islands, Tahiti, and Mauritius. Ostensibly, the centerpiece of the 1844 volume is Darwin's extensive coverage of Ascension based on the five days spent there in 1836. However, Darwin had many more days at his disposal in the Galápagos and ‘St. Jago’ (Santiago), where the Beagle stopped in the Cape Verde Islands at the outset and again near the end of the voyage. The volcanic islands where Darwin spent the most time were in the Galápagos (thirty-five days) and the Cape Verdes (twenty-nine days). In particular, those island groups make an interesting comparison with respect to the development of Darwin's ideas on tectonic uplift based on basalt flows with inter-bedded limestone formations. Chance played a huge role in what Darwin saw and did not see during his island travels. The initial visit to the Cape Verde islands was instrumental in shaping Darwin's earliest vision of a book on volcanic islands, but his time there was entirely fortuitous due to a forced change in FitzRoy's plan for a stay in the Canary Islands. Although Darwin was on the look out for limestone formations in the Galápagos islands comparable to those on Santiago in the Cape Verdes, he missed finding them due only to the vagaries of FitzRoy's charting schedule in the Galápagos. This overview looks at limestone distribution in the Cape Verde and Galápagos archipelagos as now understood and speculates on how a wider knowledge of both regions may have influenced Darwin's thinking on global patterns of island uplift and subsidence.

scholarly journals Finding Alcatrazes and early Luso-African settlement on Santiago Island, Cape Verde

Antiquity ◽  
2017 ◽  
Vol 91 (358) ◽  
Author(s):  
Christopher Evans ◽  
Marie Louise Stig Sørensen ◽  
Michael J. Allen ◽  
Jo Appleby ◽  
Tania Manuel Casimiro ◽  
...  
Keyword(s):  
Cape Verde ◽  
The South ◽  
Cape Verde Islands ◽  
Main Island ◽  
South West ◽  
Santiago Island

After the Portuguese discovered the Cape Verde Islands in AD 1456 they divided its main island, Santiago, into two governing captaincies. The founding settlement in the south-west, Cidade Velha, soon became the Islands’ capital and a thriving trade centre; in contrast, that in the east, Alcatrazes, only lasted as an official seat from 1484–1516 and is held to have ‘failed’ (see Richter 2015).

scholarly journals A STUDY OF THE FIRE SMOKE PROPAGATION IN SUBWAY STATION UNDER THE EFFECT OF PISTON WIND

2015 ◽  
Vol 21 (4) ◽  
pp. 514-523 ◽  
Author(s):  
Wei Zhong ◽  
Rui Tu ◽  
Jian Peng Yang ◽  
Tian Shui Liang
Keyword(s):  
Wind Tunnel ◽  
Large Scale ◽  
Inertial Force ◽  
Field Structure ◽  
Subway Station ◽  
Volume Flux ◽  
Ventilation Shaft ◽  
Fire Smoke ◽  
In Fire ◽  
The Impact

A running traffic train induces piston wind in the subway. The influence of piston wind on fire smoke propagation in subway is investigated numerically. The flow field structure in fire platform, temperature contours and velocity profiles at certain positions are obtained at various scenarios respectively. Three methods are adopted to reduce the impact of piston wind on smoke layers. Results show that large-scale vortexes and tremendous horizontal inertial force would be produced under the influence of piston wind; and that smoke stratification would be broken totally under its influence, therefore toxic gas would spread to subway hall through stairs. So the former smoke management system in a subway station becomes less effective. Results also show that combination of enhanced the volume flux of pressurization at the subway hall and lowering the height of smoke screens around stairs are necessary to restrict hazard smoke on the floor on fire. The bypass wind tunnel and ventilation shaft are useful to attenuate the magnitude of piston wind.

scholarly journals Flank collapse and large-scale landsliding in the Cape Verde Islands, off West Africa

2008 ◽  
Vol 9 (7) ◽  
pp. n/a-n/a ◽  
Author(s):  
D. G. Masson ◽  
T. P. Le Bas ◽  
I. Grevemeyer ◽  
W. Weinrebe
Keyword(s):  
West Africa ◽  
Large Scale ◽  
Cape Verde ◽  
Cape Verde Islands ◽  
Flank Collapse

scholarly journals What Darwin did not see: Pleistocene fossil assemblages on a high-energy coast at Ponta das Bicudas, Santiago, Cape Verde Islands

2012 ◽  
Vol 150 (1) ◽  
pp. 183-189 ◽  
Author(s):  
B. GUDVEIG BAARLI ◽  
ANA G. SANTOS ◽  
EDUARDO J. MAYORAL ◽  
JORGE LEDESMA-VÁZQUEZ ◽  
MARKES E. JOHNSON ◽  
...  
Keyword(s):  
Rocky Shore ◽  
High Energy ◽  
Cape Verde ◽  
Tidal Zone ◽  
Cape Verde Islands ◽  
Low Diversity ◽  
Fossil Assemblages ◽  
Santiago Island

AbstractTwo distinct Pleistocene assemblages from SE Santiago Island are comparable to modern analogues elsewhere in the Cape Verde Islands. A low-diversity Siderastrea radians assemblage lived atop basalt knobs surrounded by sand on a slope below a cliff. A Millepora alcicornis–Megabalanus azoricus assemblage occupied the cliff. The latter was a typical rocky-shore assemblage from a high-energy setting below the tidal zone. Bioerosion structures in basalt produced by Circolites kotoncensis and Gastrochaenolites isp. also occur there. Despite extensive studies on local limestone deposits in 1832 and 1836, lack of exposure prevented Darwin from seeing these fossils.

scholarly journals Precipitation Patterns in Cape Verde Islands: Santiago Island Case Study

2014 ◽  
Vol 04 (05) ◽  
pp. 854-865 ◽  
Author(s):  
Gerson Ernesto Varela-Lopes ◽  
Luiz Carlos Baldicero Molion
Keyword(s):  
Cape Verde ◽  
Cape Verde Islands ◽  
Precipitation Patterns ◽  
Santiago Island

Didogobius janetarum sp. nov., a new cryptobenthic goby species from the Cape Verde Islands (Teleostei: Gobiidae)

Zootaxa ◽  
2018 ◽  
Vol 4438 (2) ◽  
pp. 381 ◽  
Author(s):  
ULRICH K. SCHLIEWEN ◽  
PETER WIRTZ ◽  
MARCELO KOVAČIĆ
Keyword(s):  
Cape Verde ◽  
Cape Verde Islands ◽  
Dorsal Fin ◽  
Meristic Counts ◽  
Goby Species ◽  
Santiago Island ◽  
Posterior Quarter

Didogobius janetarum sp. nov. is described from five specimens collected from small caves and rock crevices between 12 and 20 m depth off two locations of Santiago Island, Cape Verde Islands. The species differs from all currently described congeners by the combination of the following characters: (1) 27 vertebrae, (2) second dorsal fin I + 10, (3) posterior quarter of predorsal region in front of first dorsal fin origin scaled, with several rows of cycloid scales, (4) body squamation cycloid anteriorly and ctenoid posteriorly, (5) scales in the lateral series 30–32, (6) anterior oculoscapular canal present, (7) preopercular head canal absent, (8) suborbital row 7 each a single papilla, (9) suborbital rows 2 and 4 close to orbit, and by (10) branchiostegal membranes uniformely black below preopercle, forming a V-shaped mark. Definitions for all used meristic counts are presented to serve as a reference for gobioid meristic studies. The genus is rediagnosed to accommodate recently described Didogobius species. 

scholarly journals PREDICTION OF DYNAMIC AND QUASI-STATIC IMPACTS ON VERTICAL SEA WALLS CAUSED BY AN OVERTOPPED BORE

2018 ◽  
pp. 28
Author(s):  
Maximilian Streicher ◽  
Andreas Kortenhaus ◽  
Vincent Gruwez ◽  
Bas Hofland ◽  
Xuexue Chen ◽  
...  
Keyword(s):  
Prediction Accuracy ◽  
Large Scale ◽  
Impact Force ◽  
Vertical Wall ◽  
Impact Behavior ◽  
Small Scale ◽  
Run Up ◽  
The Individual ◽  
Two Peaks ◽  
The Impact

This study comprises a detailed description of the individual overtopped bore impact processes against a vertical wall, situated on top of a dike. A twin peak force impact signal shape was observed with two distinct peaks during every impact. The two peaks were assigned consecutively to the dynamic components (thickness and velocity) or hydrostatic components (run-up of water at the wall) of the impacting bore. The two peaks were termed dynamic F1 and quasi-static F2 impact respectively. Based on available literature semi-empirical equations to describe either the dynamic F1 or quasi-static F2 impact force were investigated and the prediction accuracy evaluated using impact force data from large-scale experiments. The prediction accuracy of the dynamic F1 impacts was very low. The prediction accuracy of the quasi-static impact F2 was increased based on fitting the hydrostatic theory to the maximum run-up measurement at the wall. Based on these findings 80% of the maximum run-up height was effectively contributing to the maximum quasi-static force F2 on the wall. The results coincided well with previous small-scale studies (Chen et al. 2012). After deconstructing the process chain preceding an impact, using the physically most meaningful parameters to predict the impact force, evaluating on a range of existing approaches, and observing the scattered prediction results, it was concluded that the impact behavior is highly stochastic and statistical analysis would be more beneficial.

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