{"id":404,"date":"2014-08-31T06:49:14","date_gmt":"2014-08-31T06:49:14","guid":{"rendered":"https:\/\/blogs.futura-sciences.com\/bardintzeff\/?p=404"},"modified":"2014-08-31T06:54:51","modified_gmt":"2014-08-31T06:54:51","slug":"point-chaud-lislande","status":"publish","type":"post","link":"https:\/\/blogs.futura-sciences.com\/bardintzeff\/2014\/08\/31\/point-chaud-lislande\/","title":{"rendered":"Un point chaud sous l\u2019Islande ?"},"content":{"rendered":"

Le magmatisme en Islande r\u00e9sulte en partie du rift m\u00e9dio-Atlantique en extension, qui recoupe l\u2019\u00eele.<\/p>\n

Mais l\u2019activit\u00e9 d\u2019un \u00ab\u00a0point chaud\u00a0\u00bb s\u2019ajoute \u00e0 celui-ci, ce qui explique la dualit\u00e9 g\u00e9ochimique des roches volcaniques.<\/p>\n

\"Bardintzeff.IS<\/a><\/p>\n

Le rift m\u00e9dio-Atlantique \u00e0 Thingvellir\u00a0: un pied en Eurasie et l\u2019autre en Am\u00e9rique en quelque sorte\u00a0! (\u00a9 J.M. Bardintzeff).<\/p>\n

 <\/p>\n

Un point chaud, r\u00e9sulte d\u2019un panache, anomalie thermique qui monte de la profondeur depuis la limite manteau-noyau (situ\u00e9e \u00e0 2\u00a0900 km de profondeur).<\/p>\n

<\/p>\n

Voici ce que j\u2019\u00e9cris dans mon livre \u00ab Volcanologie \u00bb (4e \u00e9d., Dunod, 2011) :<\/p>\n

La g\u00e9om\u00e9trie d\u2019un panache \u00e9volue au cours du temps. Dans un premier temps, les panaches, sont form\u00e9s d’une \u00ab t\u00eate \u00bb, qui grossit durant l’ascension (vitesse de mont\u00e9e \u00e0 l\u2019\u00e9tat visqueux de quelques cm \u00e0 1 m.an-1, soit quelques millions d’ann\u00e9es entre l’initiation et l’arriv\u00e9e) jusqu’\u00e0 atteindre un diam\u00e8tre maximum de l\u2019ordre de 1 000 km \u00e0 la base de la lithosph\u00e8re (Griffiths et Campbell, 1990). La t\u00eate s’aplatit quand le panache est arr\u00eat\u00e9 \u00e0 la base de la lithosph\u00e8re pour former un disque de 2 000 km de diam\u00e8tre pour 180 km d’\u00e9paisseur. Dans d\u2019autres cas, la t\u00eate mesure seulement 250 km de diam\u00e8tre et forme un disque de 500 km de diam\u00e8tre (\u2026) \u00c0 ce stade, les points chauds sont particuli\u00e8rement actifs et peuvent donner naissance par fusion mantellique \u00e0 de grands plateaux basaltiques de type Deccan. Ensuite, les panaches acqui\u00e8rent l\u2019aspect plus classique qu\u2019on leur conna\u00eet, lorsque se met en place la \u00ab queue \u00bb, d’un diam\u00e8tre de l\u2019ordre de 200 km.<\/p>\n

Par exemple, le point chaud bien rep\u00e9r\u00e9 par sismique sous l\u2019Islande, centr\u00e9 sous la partie la plus active de l’\u00eele (Wolfe et al., 1997) est un cylindre quasi vertical de 300 km de diam\u00e8tre (soit plus de la moiti\u00e9 de la longueur de l\u2019\u00eele), 400 \u00e0 700 km de profondeur, avec une temp\u00e9rature sup\u00e9rieure de 200 \u00b0C \u00e0 celle du manteau avoisinant.<\/p>\n

\"Bardintzeff.IS<\/a><\/p>\n

Le crat\u00e8re du Kerid (\u00a9 J.M. Bardintzeff).<\/p>\n","protected":false},"excerpt":{"rendered":"

Le magmatisme en Islande r\u00e9sulte en partie du rift m\u00e9dio-Atlantique en extension, qui recoupe l\u2019\u00eele. Mais l\u2019activit\u00e9 d\u2019un \u00ab\u00a0point chaud\u00a0\u00bb s\u2019ajoute \u00e0 celui-ci, ce qui explique la dualit\u00e9 g\u00e9ochimique des roches volcaniques. Le rift m\u00e9dio-Atlantique \u00e0 Thingvellir\u00a0: un pied en Eurasie et l\u2019autre en Am\u00e9rique en quelque sorte\u00a0! (\u00a9 J.M. Bardintzeff).   Un point chaud, … Continuer la lecture de Un point chaud sous l\u2019Islande ?<\/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":[6],"tags":[98,103,102],"class_list":["post-404","post","type-post","status-publish","format-standard","hentry","category-actualites","tag-islande","tag-panache","tag-point-chaud"],"yoast_head":"\nUn point chaud sous l\u2019Islande ? , 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\/2014\/08\/31\/point-chaud-lislande\/\" \/>\n<meta property=\"og:locale\" content=\"fr_FR\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Un point chaud sous l\u2019Islande ? , par Jacques-Marie Bardintzeff\" \/>\n<meta property=\"og:description\" content=\"Le magmatisme en Islande r\u00e9sulte en partie du rift m\u00e9dio-Atlantique en extension, qui recoupe l\u2019\u00eele. Mais l\u2019activit\u00e9 d\u2019un \u00ab\u00a0point chaud\u00a0\u00bb s\u2019ajoute \u00e0 celui-ci, ce qui explique la dualit\u00e9 g\u00e9ochimique des roches volcaniques. Le rift m\u00e9dio-Atlantique \u00e0 Thingvellir\u00a0: un pied en Eurasie et l\u2019autre en Am\u00e9rique en quelque sorte\u00a0! (\u00a9 J.M. 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