{"id":1119,"date":"2016-02-19T18:38:41","date_gmt":"2016-02-19T18:38:41","guid":{"rendered":"https:\/\/blogs.futura-sciences.com\/bardintzeff\/?p=1119"},"modified":"2016-02-19T18:48:21","modified_gmt":"2016-02-19T18:48:21","slug":"dome-de-lave-mont-saint-helens","status":"publish","type":"post","link":"https:\/\/blogs.futura-sciences.com\/bardintzeff\/2016\/02\/19\/dome-de-lave-mont-saint-helens\/","title":{"rendered":"Le d\u00f4me de lave du mont Saint Helens"},"content":{"rendered":"<p>Le volcan mont Saint Helens, dans l&#8217;\u00e9tat de Washington, sur la c\u00f4te ouest des \u00c9tats-Unis, a \u00e9t\u00e9 le si\u00e8ge d&#8217;une \u00e9ruption paroxysmale le 18 mai 1980. Un panache cendreux (plinien) a atteint 27 km de hauteur. De nombreuses nu\u00e9es ardentes (p\u00e9l\u00e9ennes) ont \u00e9t\u00e9 \u00e9mises. Puis un d\u00f4me de lave visqueuse (dacite) s&#8217;est mis en place dans le crat\u00e8re en forme de fer \u00e0 cheval. Ce d\u00f4me correspondait au magma en grande partie d\u00e9gaz\u00e9.<\/p>\n<p>Voici un extrait de mon livre \u00ab Volcanologie \u00bb (\u00c9ditions Dunod) :<\/p>\n<p>Au mont Saint Helens, le d\u00f4me de 1980 (4 millions de m3) a grandi entre 1981 et 1983, pour atteindre en d\u00e9cembre 1983, 880 m de long, 830 m de large et 224 m de hauteur. Sa croissance a continu\u00e9 ensuite, plus lentement, jusqu\u2019en octobre 1986 : dix-sept \u00e9pisodes de croissance, chacun durant plusieurs jours \u00e0 un an, se sont succ\u00e9d\u00e9. Finalement le d\u00f4me mesurait 1 060 x 860 m soit 74 millions de m3 et sa hauteur atteignait 267 m au-dessus de son point d\u2019\u00e9mission et 350 m au-dessus de sa base nord.<\/p>\n<p><!--more--><\/p>\n<p>Un nouveau d\u00f4me s\u2019est \u00e9difi\u00e9 lors de la crise \u00e9ruptive de septembre 2004. En f\u00e9vrier 2005 il d\u00e9passait d\u00e9j\u00e0 de 160 m la hauteur de l\u2019ancien d\u00f4me des ann\u00e9es 1980. Sa croissance a cess\u00e9 en janvier 2008 pour un volume final de 95 millions de m3.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-1121\" src=\"https:\/\/blogs.futura-sciences.com\/bardintzeff\/wp-content\/uploads\/sites\/3\/2016\/02\/Bardintzeff.USA2014.8245.St_Helens.Mt_Adams-450x337.jpg\" alt=\"Bardintzeff.USA2014.8245.St_Helens.Mt_Adams\" width=\"481\" height=\"360\" srcset=\"https:\/\/blogs.futura-sciences.com\/bardintzeff\/wp-content\/uploads\/sites\/3\/2016\/02\/Bardintzeff.USA2014.8245.St_Helens.Mt_Adams-450x337.jpg 450w, https:\/\/blogs.futura-sciences.com\/bardintzeff\/wp-content\/uploads\/sites\/3\/2016\/02\/Bardintzeff.USA2014.8245.St_Helens.Mt_Adams-768x576.jpg 768w, https:\/\/blogs.futura-sciences.com\/bardintzeff\/wp-content\/uploads\/sites\/3\/2016\/02\/Bardintzeff.USA2014.8245.St_Helens.Mt_Adams-1024x768.jpg 1024w, https:\/\/blogs.futura-sciences.com\/bardintzeff\/wp-content\/uploads\/sites\/3\/2016\/02\/Bardintzeff.USA2014.8245.St_Helens.Mt_Adams.jpg 1134w\" sizes=\"auto, (max-width: 481px) 100vw, 481px\" \/><\/p>\n<p>Un d\u00f4me de lave visqueuse dans le crat\u00e8re en fer \u00e0 cheval du mont Saint Helens. On aper\u00e7oit le mont Adams en arri\u00e8re-plan. Photo prise le 25 juillet 2014 (\u00a9 J.M. Bardintzeff).<\/p>\n<p>Nous avons pu survoler le crat\u00e8re du mont Saint Helens en h\u00e9licopt\u00e8re en juillet 2014, dans le cadre d&#8217;un p\u00e9riple dans l&#8217;Ouest am\u00e9ricain, avec 80 jours voyages (guide : Sylvain Chermette, conseiller scientifique : Jacques-Marie Bardintzeff, volcanologue).<\/p>\n<!-- AddThis Advanced Settings generic via filter on the_content --><!-- AddThis Share Buttons generic via filter on the_content -->","protected":false},"excerpt":{"rendered":"<p>Le volcan mont Saint Helens, dans l&#8217;\u00e9tat de Washington, sur la c\u00f4te ouest des \u00c9tats-Unis, a \u00e9t\u00e9 le si\u00e8ge d&#8217;une \u00e9ruption paroxysmale le 18 mai 1980. Un panache cendreux (plinien) a atteint 27 km de hauteur. De nombreuses nu\u00e9es ardentes (p\u00e9l\u00e9ennes) ont \u00e9t\u00e9 \u00e9mises. Puis un d\u00f4me de lave visqueuse (dacite) s&#8217;est mis en place &hellip; <a href=\"https:\/\/blogs.futura-sciences.com\/bardintzeff\/2016\/02\/19\/dome-de-lave-mont-saint-helens\/\" class=\"more-link\">Continuer la lecture de <span class=\"screen-reader-text\">Le d\u00f4me de lave du mont Saint Helens<\/span>  <span class=\"meta-nav\">&rarr;<\/span><\/a><!-- AddThis Advanced Settings generic via filter on get_the_excerpt --><!-- AddThis Share Buttons generic via filter on get_the_excerpt --><\/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":[257,21,218,378,379,380,17,381,97,3,13,382],"class_list":["post-1119","post","type-post","status-publish","format-standard","hentry","category-voyages","tag-80-jours-voyages","tag-bardintzeff","tag-chermette","tag-dacite","tag-dome-de-lave","tag-dunod","tag-eruption","tag-mont-adams","tag-mont-saint-helens","tag-volcan","tag-volcanologue","tag-washington"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v24.1 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Le d\u00f4me de lave du mont Saint Helens, 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\/2016\/02\/19\/dome-de-lave-mont-saint-helens\/\" \/>\n<meta property=\"og:locale\" content=\"fr_FR\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Le d\u00f4me de lave du mont Saint Helens, par Jacques-Marie Bardintzeff\" \/>\n<meta property=\"og:description\" content=\"Le volcan mont Saint Helens, dans l&#8217;\u00e9tat de Washington, sur la c\u00f4te ouest des \u00c9tats-Unis, a \u00e9t\u00e9 le si\u00e8ge d&#8217;une \u00e9ruption paroxysmale le 18 mai 1980. Un panache cendreux (plinien) a atteint 27 km de hauteur. De nombreuses nu\u00e9es ardentes (p\u00e9l\u00e9ennes) ont \u00e9t\u00e9 \u00e9mises. 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