![\"Bardintzeff.Cap_Vert.SAM_1734.col_Forquinha\"](\"https:\/\/blogs.futura-sciences.com\/bardintzeff\/wp-content\/uploads\/sites\/3\/2015\/06\/Bardintzeff.Cap_Vert.SAM_1734.col_Forquinha-450x338.jpg\")
<\/a><\/p>\nLa Vall\u00e9e des dykes au col de Forquinha, Santo Ant\u00e3o, Cap-Vert (\u00a9 J.M. Bardintzeff).<\/p>\n
<\/p>\n
Extrait de mon livre \u00ab Volcanologie \u00bb (Dunod, 4e \u00e9dition, 2011) :<\/p>\n
Les intrusions
\nLa lave, en montant vers la surface, s\u2019insinue dans l\u2019\u00e9difice volcanique \u00e0 la faveur de zones de faiblesse (limites de coul\u00e9es, failles, etc.) et se met en place \u00e0 l\u2019int\u00e9rieur de celui-ci sous forme d\u2019intrusions. Quand le mouvement cesse, soit parce que la lave n\u2019atteint pas le sommet, soit parce que l\u2019alimentation s\u2019arr\u00eate, la lave fige sur place. En se refroidissant, elle acquiert une prismation toujours perpendiculaire aux \u00e9pontes. Ult\u00e9rieurement, l\u2019\u00e9rosion met ces structures internes \u00e0 l\u2019affleurement, voire m\u00eame en relief par d\u00e9chaussement.<\/p>\n
* Les dykes r\u00e9sultent du remplissage de fractures verticales, radiaires ou concentriques \u00e0 l\u2019\u00e9difice. D\u00e9gag\u00e9s, ils apparaissent sous forme de petits murs (d\u2019ailleurs ce mot signifie \u00ab mur \u00bb en langue d\u2019origine celtique parl\u00e9e en Ecosse), \u00e0 prismation horizontale mimant une construction.<\/p>\n
* Les sills sont des \u00ab filons-couches \u00bb plus ou moins horizontaux, respectant la stratigraphie g\u00e9n\u00e9rale du volcan.
\nLes \u00e9paisseurs des dykes et des sills, souvent inf\u00e9rieures au m\u00e8tre, peuvent d\u00e9passer une dizaine de m\u00e8tres. La longueur d\u2019un dyke peut atteindre plusieurs centaines de m\u00e8tres.<\/p>\n
* Enfin les necks, caract\u00e9ris\u00e9s par une prismation radiaire, r\u00e9sultent d\u2019anciennes chemin\u00e9es volcaniques combl\u00e9es.<\/p>\n","protected":false},"excerpt":{"rendered":"
Un dyke est un filon d\u2019alimentation rempli de lave qui s\u2019est solidifi\u00e9e. D\u00e9gag\u00e9 ensuite par l\u2019\u00e9rosion, il mime un petit mur d\u2019autant plus qu\u2019il est souvent prism\u00e9. Sur l\u2019\u00eele de Santo Ant\u00e3o au Cap-Vert, au col de Forquinha, on d\u00e9couvre l\u2019extraordinaire \u00ab Vall\u00e9e des dykes \u00bb, une v\u00e9ritable visite \u00e0 l\u2019int\u00e9rieur d\u2019un volcan ! La … Continuer la lecture de Images de volcan : la Vall\u00e9e des dykes<\/span> →<\/span><\/a><\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_links_to":"","_links_to_target":""},"categories":[8],"tags":[115,180,182,179,181,3],"class_list":["post-657","post","type-post","status-publish","format-standard","hentry","category-voyages","tag-cap-vert","tag-dyke","tag-neck","tag-santo-antao","tag-sill","tag-volcan"],"yoast_head":"\nImages de volcan : la Vall\u00e9e des dykes, par Jacques-Marie Bardintzeff<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/blogs.futura-sciences.com\/bardintzeff\/2015\/06\/06\/images-de-volcan-la-vallee-des-dykes\/\" \/>\n<meta property=\"og:locale\" content=\"fr_FR\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Images de volcan : la Vall\u00e9e des dykes, par Jacques-Marie Bardintzeff\" \/>\n<meta property=\"og:description\" content=\"Un dyke est un filon d\u2019alimentation rempli de lave qui s\u2019est solidifi\u00e9e. D\u00e9gag\u00e9 ensuite par l\u2019\u00e9rosion, il mime un petit mur d\u2019autant plus qu\u2019il est souvent prism\u00e9. Sur l\u2019\u00eele de Santo Ant\u00e3o au Cap-Vert, au col de Forquinha, on d\u00e9couvre l\u2019extraordinaire \u00ab Vall\u00e9e des dykes \u00bb, une v\u00e9ritable visite \u00e0 l\u2019int\u00e9rieur d\u2019un volcan ! La … Continuer la lecture de Images de volcan : la Vall\u00e9e des dykes →\" \/>\n<meta property=\"og:url\" content=\"https:\/\/blogs.futura-sciences.com\/bardintzeff\/2015\/06\/06\/images-de-volcan-la-vallee-des-dykes\/\" \/>\n<meta property=\"og:site_name\" content=\"VOLCANMANIA : le blog de Jacques-Marie BARDINTZEFF, volcanologue\" \/>\n<meta property=\"article:published_time\" content=\"2015-06-06T11:44:28+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2015-06-06T11:51:37+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/blogs.futura-sciences.com\/bardintzeff\/wp-content\/uploads\/sites\/3\/2015\/06\/Bardintzeff.Cap_vert.SAM_1690.col_Forquinha.jpg\" \/>\n\t<meta property=\"og:image:width\" content=\"1417\" \/>\n\t<meta property=\"og:image:height\" content=\"1063\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/jpeg\" \/>\n<meta name=\"author\" content=\"jmbardintzeff\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"\u00c9crit par\" \/>\n\t<meta name=\"twitter:data1\" content=\"jmbardintzeff\" \/>\n\t<meta name=\"twitter:label2\" content=\"Dur\u00e9e de lecture estim\u00e9e\" \/>\n\t<meta name=\"twitter:data2\" content=\"2 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/blogs.futura-sciences.com\/bardintzeff\/2015\/06\/06\/images-de-volcan-la-vallee-des-dykes\/\",\"url\":\"https:\/\/blogs.futura-sciences.com\/bardintzeff\/2015\/06\/06\/images-de-volcan-la-vallee-des-dykes\/\",\"name\":\"Images de volcan : la Vall\u00e9e des dykes, par Jacques-Marie Bardintzeff\",\"isPartOf\":{\"@id\":\"https:\/\/blogs.futura-sciences.com\/bardintzeff\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\/\/blogs.futura-sciences.com\/bardintzeff\/2015\/06\/06\/images-de-volcan-la-vallee-des-dykes\/#primaryimage\"},\"image\":{\"@id\":\"https:\/\/blogs.futura-sciences.com\/bardintzeff\/2015\/06\/06\/images-de-volcan-la-vallee-des-dykes\/#primaryimage\"},\"thumbnailUrl\":\"https:\/\/blogs.futura-sciences.com\/bardintzeff\/wp-content\/uploads\/sites\/3\/2015\/06\/Bardintzeff.Cap_vert.SAM_1690.col_Forquinha-450x338.jpg\",\"datePublished\":\"2015-06-06T11:44:28+00:00\",\"dateModified\":\"2015-06-06T11:51:37+00:00\",\"author\":{\"@id\":\"https:\/\/blogs.futura-sciences.com\/bardintzeff\/#\/schema\/person\/974e1e0324e3e06f08253784e8eca61e\"},\"inLanguage\":\"fr-FR\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/blogs.futura-sciences.com\/bardintzeff\/2015\/06\/06\/images-de-volcan-la-vallee-des-dykes\/\"]}]},{\"@type\":\"ImageObject\",\"inLanguage\":\"fr-FR\",\"@id\":\"https:\/\/blogs.futura-sciences.com\/bardintzeff\/2015\/06\/06\/images-de-volcan-la-vallee-des-dykes\/#primaryimage\",\"url\":\"https:\/\/blogs.futura-sciences.com\/bardintzeff\/wp-content\/uploads\/sites\/3\/2015\/06\/Bardintzeff.Cap_vert.SAM_1690.col_Forquinha.jpg\",\"contentUrl\":\"https:\/\/blogs.futura-sciences.com\/bardintzeff\/wp-content\/uploads\/sites\/3\/2015\/06\/Bardintzeff.Cap_vert.SAM_1690.col_Forquinha.jpg\",\"width\":1417,\"height\":1063},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/blogs.futura-sciences.com\/bardintzeff\/#website\",\"url\":\"https:\/\/blogs.futura-sciences.com\/bardintzeff\/\",\"name\":\"VOLCANMANIA : le blog de Jacques-Marie BARDINTZEFF, volcanologue\",\"description\":\"Les volcans ? 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![\"Bardintzeff.Cap_vert.SAM_1690.col_Forquinha\"](\"https:\/\/blogs.futura-sciences.com\/bardintzeff\/wp-content\/uploads\/sites\/3\/2015\/06\/Bardintzeff.Cap_vert.SAM_1690.col_Forquinha.jpg\")
<\/a><\/p>\n