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Avaliação dos perigos vulcânicos e fenómenos associados na Ilha do Fogo (Cabo Verde) : implicações para o planeamento de emergência e ordenamento do território
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| Resumo, Índice, Introdução | 253.74 KB | Adobe PDF | ||
| Documento Principal | 49 MB | Adobe PDF |
Authors
Abstract(s)
O arquipélago de Cabo Verde é composto por 10 ilhas e vários ilhéus de origem vulcânica, sendo a ilha do Fogo a única onde se registaram erupções históricas. É neste contexto que o presente trabalho se debruça sobre a avaliação dos perigos vulcânicos e fenómenos associados nesta ilha, e nas respetivas implicações em termos de planeamento de emergência e ordenamento do território.
Para se compreender melhor o vulcanismo da ilha do Fogo, fez-se o enquadramento geotectónico do arquipélago e da ilha, foi analisada bibliografia especializada e cartografadas as principais formas e produtos vulcânicos relacionados com a atividade mais recente. Foram também analisados e calculados os parâmetros morfométricos dos cones de escórias, comparando-se os resultados obtidos com os determinados para outras regiões vulcânicas.
Paralelamente, fez-se a pesquisa, revisão e análise de todos os relatos encontrados sobre erupções vulcânicas e sismos históricos ocorridos na ilha do Fogo. Constatou-se que desde o ano de 1500 ocorreram cerca de 31 erupções vulcânicas localizadas no interior da caldeira do Vulcão do Fogo e no Pico do Fogo, cujos estilos eruptivos foram essencialmente havaiano e estromboliano e que tiveram significativos impactes económicos, sociais, ambientais e culturais.
Com base na caracterização da história eruptiva desde 1500 identificaram-se os diversos perigos vulcânicos diretos e indiretos. Os primeiros correspondem às escoadas lávicas e piroclastos de queda de natureza basáltica, e gases vulcânicos. Os segundos são, sobretudo, os sismos que antecederam os vários episódios eruptivos.
Para se efetuar a análise da suscetibilidade ao desenvolvimento de escoadas lávicas, realizaram-se vários ensaios utilizando o modelo de simulação “Grapel 4”, incluído na ferramenta de SIG designada por VORIS, para se determinarem os valores mais adequados para os parâmetros da modelação. Concluiu-se que o modelo numérico de elevação de terreno com células de 50 metros era o mais indicado. As áreas fonte consideradas são as diretamente relacionadas com a distribuição dos centros emissores pré-existentes e com as estruturas tectónicas. Foram assim produzidas duas cartas de suscetibilidade a escoadas lávicas, uma ao nível da ilha e outra considerando apenas as áreas fonte situadas no interior da caldeira. Ambas foram posteriormente utilizadas nos estudos de vulnerabilidades.
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ABSTRACT: The Cape Verde archipelago consists of 10 islands and several islets of volcanic origin, being Fogo island the only one where historical volcanism has occurred. In this context, the present work focuses on the assessment of volcanic hazards and associated phenomena on this island, and in its respective implications for emergency and land use planning. To better understand the volcanism of Fogo island, the archipelago and the island geotectonic setting was characterized, the scientific literature was analysed and the mapping of the main volcanic forms and products related with the most recent activity was performed. Also, the morphometric parameters of cinder cones were analyzed and calculated and the results were compared with those obtained from similar studies for other volcanic regions. At the same time the research, review and analysis of all available accounts on Fogo island historical volcanic eruptions and earthquakes was performed. It was found that since the year 1500 about 31 volcanic eruptions had occurred inside the caldera of Fogo volcano and at Pico do Fogo whose eruptive styles were essentially Hawaiian and Strombolian causing significant economic, social, environmental and cultural impacts. Based on the characterization of the post 1500 eruptive history the various direct and indirect volcanic hazards were identified. The first ones correspond to lava flows and pyroclast fallout of basaltic nature and volcanic gases. The latter are mainly earthquakes that preceded several eruptive episodes In order to perform the analysis the susceptibility to lava flows on Fogo island, several tests were done using the simulation model "Grapel 4", included in the GIS tool VORIS to determine the most appropriate values for the modelling parameters. It was concluded that the most suitable numerical model of terrain elevation was the one with cells of 50 meters. The source areas defined are those directly related to the distribution of pre-existing eruptive centres and tectonic structures. Two susceptibility maps of lava flows were produced, one at the island scale and another based only in the source areas located within the caldera. Both were later used for vulnerability studies. Regarding the vulnerability to seismic and lava flows hazard the major exposed elements, including people, buildings, roads and water sources for seismic hazard and lava flows were analysed. [...].
ABSTRACT: The Cape Verde archipelago consists of 10 islands and several islets of volcanic origin, being Fogo island the only one where historical volcanism has occurred. In this context, the present work focuses on the assessment of volcanic hazards and associated phenomena on this island, and in its respective implications for emergency and land use planning. To better understand the volcanism of Fogo island, the archipelago and the island geotectonic setting was characterized, the scientific literature was analysed and the mapping of the main volcanic forms and products related with the most recent activity was performed. Also, the morphometric parameters of cinder cones were analyzed and calculated and the results were compared with those obtained from similar studies for other volcanic regions. At the same time the research, review and analysis of all available accounts on Fogo island historical volcanic eruptions and earthquakes was performed. It was found that since the year 1500 about 31 volcanic eruptions had occurred inside the caldera of Fogo volcano and at Pico do Fogo whose eruptive styles were essentially Hawaiian and Strombolian causing significant economic, social, environmental and cultural impacts. Based on the characterization of the post 1500 eruptive history the various direct and indirect volcanic hazards were identified. The first ones correspond to lava flows and pyroclast fallout of basaltic nature and volcanic gases. The latter are mainly earthquakes that preceded several eruptive episodes In order to perform the analysis the susceptibility to lava flows on Fogo island, several tests were done using the simulation model "Grapel 4", included in the GIS tool VORIS to determine the most appropriate values for the modelling parameters. It was concluded that the most suitable numerical model of terrain elevation was the one with cells of 50 meters. The source areas defined are those directly related to the distribution of pre-existing eruptive centres and tectonic structures. Two susceptibility maps of lava flows were produced, one at the island scale and another based only in the source areas located within the caldera. Both were later used for vulnerability studies. Regarding the vulnerability to seismic and lava flows hazard the major exposed elements, including people, buildings, roads and water sources for seismic hazard and lava flows were analysed. [...].
Description
Tese de Doutoramento, Geologia, especialidade de Vulcanologia, 27 de outubro de 2016, Universidade dos Açores.
Keywords
Escoada Lávica Geologia Geomorfologia Recursos Hídricos Vulcanismo Vulcanologia Ilha do Fogo (Cabo Verde) Cabo Verde Volcanic Eruptions Volcanism Fogo Island Cape Verde
Citation
Cabral, Jeremias Alves. "Avaliação dos perigos vulcânicos e fenómenos associados na Ilha do Fogo (Cabo Verde): implicações para o planeamento de emergência e ordenamento do território". 2016. 281 p., A-74. (Tese de Doutoramento em Geologia, especialidade de Vulcanologia). Ponta Delgada: Universidade dos Açores, 2015. [Consult. Dia Mês Ano]. Disponível em www:<http://hdl.handle.net/10400.3/5245>.