{"id":4720,"date":"2009-01-07T18:39:40","date_gmt":"2009-01-07T16:39:40","guid":{"rendered":"http:\/\/www.laterredufutur.com\/accueil1\/?p=4720"},"modified":"2015-04-13T18:42:00","modified_gmt":"2015-04-13T16:42:00","slug":"il-y-a-18000-ans","status":"publish","type":"post","link":"https:\/\/www.laterredufutur.com\/accueil\/il-y-a-18000-ans\/","title":{"rendered":"Il y a 18000 ans"},"content":{"rendered":"<div class=\"1665f18d14f35dd9e7566e1a8ac9a3e9\" data-index=\"1\" style=\"float: none; margin:10px 0 10px 0; text-align:center;\">\n<script async src=\"https:\/\/pagead2.googlesyndication.com\/pagead\/js\/adsbygoogle.js\"><\/script>\r\n<ins class=\"adsbygoogle\"\r\n     style=\"display:block; text-align:center;\"\r\n     data-ad-layout=\"in-article\"\r\n     data-ad-format=\"fluid\"\r\n     data-ad-client=\"ca-pub-2860849627502538\"\r\n     data-ad-slot=\"3019501113\"><\/ins>\r\n<script>\r\n     (adsbygoogle = window.adsbygoogle || []).push({});\r\n<\/script>\n<\/div>\n<p>Le climat d&rsquo;une \u00e8re glaciaire n&rsquo;est pas n\u00e9cessairement uniforme : des p\u00e9riodes interglaciaires peuvent alterner avec des p\u00e9riodes de gel. M\u00eame au c\u0153ur d&rsquo;une glaciation donc, le thermom\u00e8tre ne cesse de souffler le chaud et le froid.<br \/>\nIl est donc important de ne pas confondre \u00e8re et p\u00e9riodes glaciaire.<\/p>\n<p>Ainsi on d\u00e9nombre cinq grandes glaciations dans l&rsquo;histoire de la plan\u00e8te. Mais chacune est constitu\u00e9e de successions, selon une fr\u00e9quence de dizaines de milliers d&rsquo;ann\u00e9es, de p\u00e9riodes glaciaires et interglaciaires. Elles-m\u00eames \u00e9tant encore divisibles en intervalles plut\u00f4t chauds ou froids si l&rsquo;on observe le climat \u00e0 une \u00e9chelle plus fine.<\/p>\n<p>Pour preuve de la succession de ces p\u00e9riodes: il y a 18 000 ans, la Terre traverse un maximum glaciaire. A peine 7 000 \u00e0 8 000 ans plus tard, le climat se r\u00e9chauffe : les glaciers continentaux commencent \u00e0 se retirer !<\/p>\n<p>Depuis la fin de la derni\u00e8re p\u00e9riode de glaciation il y a 18 000 ans, le climat est plus cl\u00e9ment et relativement stable. Nous nous trouvons donc dans cette p\u00e9riode o\u00f9 il r\u00e8gne en moyenne 15\u00b0C sur l&rsquo;ensemble de la plan\u00e8te.<br \/>\nPourtant, et bien que ce soit peut-\u00eatre difficile \u00e0 croire, nous sommes en p\u00e9riode interglaciaire\u2026 d&rsquo;une glaciation !<\/p>\n<p><img data-recalc-dims=\"1\" decoding=\"async\" src=\"https:\/\/i0.wp.com\/www.laterredufutur.com\/spaw\/images\/nivomer1.gif\" alt=\"\" \/><\/p><div class=\"1665f18d14f35dd9e7566e1a8ac9a3e9\" data-index=\"2\" style=\"float: none; margin:10px 0 10px 0; text-align:center;\">\n<script async src=\"https:\/\/pagead2.googlesyndication.com\/pagead\/js\/adsbygoogle.js\"><\/script>\r\n<ins class=\"adsbygoogle\"\r\n     style=\"display:block; text-align:center;\"\r\n     data-ad-layout=\"in-article\"\r\n     data-ad-format=\"fluid\"\r\n     data-ad-client=\"ca-pub-2860849627502538\"\r\n     data-ad-slot=\"3019501113\"><\/ins>\r\n<script>\r\n     (adsbygoogle = window.adsbygoogle || []).push({});\r\n<\/script>\n<\/div>\n\n<p>La terre est soumise \u00e0 des fluctuations climatiques globales. A des p\u00e9riodes froides succ\u00e8dent des p\u00e9riodes plus chaudes et inversement. Ces fluctuations se traduisent par des variations du niveau moyen des mers et des oc\u00e9ans. Au cours des p\u00e9riodes froides, l&rsquo;eau liquide se r\u00e9tracte et davantage d&rsquo;eau solide est mobilis\u00e9e au niveau des inlandsis et des glaciers.<br \/>\nOn peut mettre directement en rapport le pourcentage d&rsquo;Oxyg\u00e8ne 18 dans l&rsquo;eau avec la temp\u00e9rature et le niveau de la mer.<br \/>\nD&rsquo;apr\u00e8s la th\u00e9orie de Croll-Milankovitch, les climats terrestres sont sous la d\u00e9pendance d&rsquo;un for\u00e7age astronomique. Trois param\u00e8tres p\u00e9riodiques affectent l&rsquo;insolation terrestre:<\/p>\n<p>l&rsquo;excentricit\u00e9 de l&rsquo;orbite terrestre (p\u00e9riode d&rsquo;environ 100 000 ans)<br \/>\nl&rsquo;obliquit\u00e9 de l&rsquo;axe de rotation de la terre par rapport au plan de l&rsquo;\u00e9cliptique (p\u00e9riode d&rsquo;environ 41 000 ans)<br \/>\nla pr\u00e9cession de l&rsquo;axe des p\u00f4les (p\u00e9riode d&rsquo;environ 22 000 ans).<\/p>\n<p><img data-recalc-dims=\"1\" decoding=\"async\" src=\"https:\/\/i0.wp.com\/www.laterredufutur.com\/spaw\/images\/maxglac.jpg\" alt=\"\" \/><\/p>\n<p>La Manche \u00e0 cette \u00e9poque \u00e9tait exond\u00e9e et la ligne de rivage \u00e9tait situ\u00e9e \u00e0 l&rsquo;Ouest du Finist\u00e8re (niveau des mers \u00e0 -125 m par rapport \u00e0 l&rsquo;actuel)<br \/>\nLa temp\u00e9rature moyenne du globe n&rsquo;\u00e9tait que de 4\u00b0 inf\u00e9rieure \u00e0 l&rsquo;actuelle.<\/p>\n<p>Il y a 18 000 ans, la derni\u00e8re grande glaciation de l&rsquo;Am\u00e9rique du nord avait atteint son apog\u00e9e et la r\u00e9gion de Montr\u00e9al \u00e9tait alors recouvertes par 2 kilom\u00e8tres d&rsquo;\u00e9paisseur de glace.<\/p>\n<p>sources : <a href=\"http:\/\/www.univ-lehavre.fr\/\">http:\/\/www.univ-lehavre.fr\/<\/a>\u00a0\/ <a href=\"http:\/\/www.unites.uqam.ca\/\">http:\/\/www.unites.uqam.ca\/<\/a>\u00a0\/ <a href=\"http:\/\/climatevolution.free.fr\/\">http:\/\/climatevolution.free.fr\/<\/a><\/p>\n<p class=\"bawpvc-ajax-counter\" data-id=\"4720\">(6596)<\/p>\n<!--CusAds0-->\n<div style=\"font-size: 0px; height: 0px; line-height: 0px; margin: 0; padding: 0; clear: both;\"><\/div>","protected":false},"excerpt":{"rendered":"<p>Le climat d&rsquo;une \u00e8re glaciaire n&rsquo;est pas n\u00e9cessairement uniforme : des p\u00e9riodes interglaciaires peuvent alterner avec des p\u00e9riodes de gel&#8230;.<\/p>\n","protected":false},"author":1,"featured_media":4721,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"ngg_post_thumbnail":0,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[33],"tags":[3549,2438,153,1333,157,3550,47,436],"class_list":["post-4720","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-archeologie","tag-18-000-ans","tag-archeologie","tag-froid","tag-glaciation","tag-glaciers","tag-milankovitch","tag-neige","tag-passe","wpcat-33-id"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/i0.wp.com\/www.laterredufutur.com\/accueil\/wp-content\/uploads\/2015\/04\/glace_18000ans.jpg?fit=305%2C277&ssl=1","jetpack_shortlink":"https:\/\/wp.me\/p631RN-1e8","jetpack-related-posts":[{"id":2677,"url":"https:\/\/www.laterredufutur.com\/accueil\/glaciations-eres-et-periodes-glaciaires\/","url_meta":{"origin":4720,"position":0},"title":"Glaciations (\u00e9res et p\u00e9riodes glaciaires)","author":"Admin","date":"1 f\u00e9vrier 2005","format":false,"excerpt":"De l'avis de la majorit\u00e9 des sp\u00e9cialistes, ces variations climatiques se sont produites \u00e0 10 reprises au moins, espac\u00e9es d\u2019environ 100 000 ans. Mais la p\u00e9riode des dernieres 400 000 ann\u00e9es du Quaternaire est bien connues et d\u00e9taill\u00e9e, et comporte 4 grandes p\u00e9riodes principales : \u00a0 600 000-540 000 ans\u2026","rel":"","context":"Dans &quot;Arch\u00e9ologie&quot;","block_context":{"text":"Arch\u00e9ologie","link":"https:\/\/www.laterredufutur.com\/accueil\/sujets\/archeologie\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.laterredufutur.com\/spaw\/images\/remont4.jpeg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":8939,"url":"https:\/\/www.laterredufutur.com\/accueil\/un-cycle-de-400000-ans-et-future-periode-glaciaire\/","url_meta":{"origin":4720,"position":1},"title":"Un cycle de 400000 ans et future p\u00e9riode glaciaire","author":"Admin","date":"4 novembre 2015","format":false,"excerpt":"L'explication des alternances entre p\u00e9riodes glaciaires et interglaciaires, qui dans l'histoire de la Terre sont caract\u00e9ristiques de la seule p\u00e9riode quaternaire, a \u00e9t\u00e9 propos\u00e9e dans les ann\u00e9es 1910 par le math\u00e9maticien serbe Milutin Milankovich, qui s'est int\u00e9ress\u00e9 \u00e0 l'orbite de la Terre autour du soleil. Milankovich d\u00e9couvre trois cycles orbitaux\u2026","rel":"","context":"Dans &quot;Arch\u00e9ologie&quot;","block_context":{"text":"Arch\u00e9ologie","link":"https:\/\/www.laterredufutur.com\/accueil\/sujets\/archeologie\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.laterredufutur.com\/accueil\/wp-content\/uploads\/2015\/10\/coucherdesoleil-polenord.jpg?fit=750%2C562&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.laterredufutur.com\/accueil\/wp-content\/uploads\/2015\/10\/coucherdesoleil-polenord.jpg?fit=750%2C562&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/www.laterredufutur.com\/accueil\/wp-content\/uploads\/2015\/10\/coucherdesoleil-polenord.jpg?fit=750%2C562&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/www.laterredufutur.com\/accueil\/wp-content\/uploads\/2015\/10\/coucherdesoleil-polenord.jpg?fit=750%2C562&ssl=1&resize=700%2C400 2x"},"classes":[]},{"id":15659,"url":"https:\/\/www.laterredufutur.com\/accueil\/quand-est-ce-que-les-ages-glaciaires-arrivent-ils\/","url_meta":{"origin":4720,"position":2},"title":"Quand est ce que les ages glaciaires arrivent ils ?","author":"Admin","date":"15 septembre 2017","format":false,"excerpt":"La derni\u00e8re p\u00e9riode glaciaire a entra\u00een\u00e9 l'arriv\u00e9e du mammouth laineux et la vaste expansion des glaciers. Mais ce n'est que l'un des nombreux \u00e9pisodes qui ont refroidi la Terre dans l'histoire de notre plan\u00e8te depuis 4,5 milliards d'ann\u00e9es. Alors, \u00e0 quelle fr\u00e9quence surviennent les p\u00e9riodes de glace, et quand le\u2026","rel":"","context":"Dans &quot;Climat&quot;","block_context":{"text":"Climat","link":"https:\/\/www.laterredufutur.com\/accueil\/sujets\/climat\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.laterredufutur.com\/accueil\/wp-content\/uploads\/2015\/09\/glace-et-banquise.jpg?fit=1024%2C768&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.laterredufutur.com\/accueil\/wp-content\/uploads\/2015\/09\/glace-et-banquise.jpg?fit=1024%2C768&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/www.laterredufutur.com\/accueil\/wp-content\/uploads\/2015\/09\/glace-et-banquise.jpg?fit=1024%2C768&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/www.laterredufutur.com\/accueil\/wp-content\/uploads\/2015\/09\/glace-et-banquise.jpg?fit=1024%2C768&ssl=1&resize=700%2C400 2x"},"classes":[]},{"id":26762,"url":"https:\/\/www.laterredufutur.com\/accueil\/les-scientifiques-font-correspondre-les-cycles-de-lere-glaciaire-de-la-terre-avec-les-changements-dorbite\/","url_meta":{"origin":4720,"position":3},"title":"Les scientifiques font correspondre les cycles de l&rsquo;\u00e8re glaciaire de la Terre avec les changements d&rsquo;orbite","author":"Admin","date":"13 mars 2025","format":false,"excerpt":"Selon les scientifiques, la Terre \u00e9voluerait d'elle-m\u00eame vers une nouvelle p\u00e9riode glaciaire dans environ 10 000 ans. Mais les \u00e9missions de gaz \u00e0 effet de serre de l'humanit\u00e9 pourraient avoir radicalement modifi\u00e9 la trajectoire du climat. Il y a environ 2,5 millions d'ann\u00e9es, la Terre est entr\u00e9e dans une \u00e8re\u2026","rel":"","context":"Dans &quot;Climat&quot;","block_context":{"text":"Climat","link":"https:\/\/www.laterredufutur.com\/accueil\/sujets\/climat\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.laterredufutur.com\/accueil\/wp-content\/uploads\/2019\/03\/ere-glaciaire-terre.jpg?fit=1200%2C683&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.laterredufutur.com\/accueil\/wp-content\/uploads\/2019\/03\/ere-glaciaire-terre.jpg?fit=1200%2C683&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/www.laterredufutur.com\/accueil\/wp-content\/uploads\/2019\/03\/ere-glaciaire-terre.jpg?fit=1200%2C683&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/www.laterredufutur.com\/accueil\/wp-content\/uploads\/2019\/03\/ere-glaciaire-terre.jpg?fit=1200%2C683&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/www.laterredufutur.com\/accueil\/wp-content\/uploads\/2019\/03\/ere-glaciaire-terre.jpg?fit=1200%2C683&ssl=1&resize=1050%2C600 3x"},"classes":[]},{"id":25558,"url":"https:\/\/www.laterredufutur.com\/accueil\/leurope-a-la-fin-de-lere-glaciaire\/","url_meta":{"origin":4720,"position":4},"title":"L&rsquo;Europe \u00e0 la fin de l&rsquo;\u00e8re glaciaire","author":"Admin","date":"3 f\u00e9vrier 2024","format":false,"excerpt":"Voici \u00e0 quoi ressemblait l'Europe \u00e0 la fin de la derni\u00e8re p\u00e9riode glaciaire (vers 10 000 av. J.-C.). Elle \u00e9tait encore plus unifi\u00e9e qu'aujourd'hui, n'est-ce pas ? Quoi qu'il en soit, la derni\u00e8re p\u00e9riode glaciaire s'est d\u00e9roul\u00e9e de la fin de l'interglaciaire Eemian \u00e0 la fin du Younger Dryas, soit\u2026","rel":"","context":"Dans &quot;Arch\u00e9ologie&quot;","block_context":{"text":"Arch\u00e9ologie","link":"https:\/\/www.laterredufutur.com\/accueil\/sujets\/archeologie\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.laterredufutur.com\/accueil\/wp-content\/uploads\/2024\/01\/europe-a-la-fin-de-l-age-glaciaire.jpg?fit=750%2C420&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.laterredufutur.com\/accueil\/wp-content\/uploads\/2024\/01\/europe-a-la-fin-de-l-age-glaciaire.jpg?fit=750%2C420&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/www.laterredufutur.com\/accueil\/wp-content\/uploads\/2024\/01\/europe-a-la-fin-de-l-age-glaciaire.jpg?fit=750%2C420&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/www.laterredufutur.com\/accueil\/wp-content\/uploads\/2024\/01\/europe-a-la-fin-de-l-age-glaciaire.jpg?fit=750%2C420&ssl=1&resize=700%2C400 2x"},"classes":[]},{"id":9803,"url":"https:\/\/www.laterredufutur.com\/accueil\/lage-de-glace-de-lamerique\/","url_meta":{"origin":4720,"position":5},"title":"L&rsquo;\u00e2ge de glace de l&rsquo;Am\u00e9rique","author":"Admin","date":"16 d\u00e9cembre 2015","format":false,"excerpt":"A quoi correspondent les \u00e2ges de glace et quand sera la prochaine \u00e9ch\u00e9ance ? L'animation infographique permet de retracer l'histoire glaciaire de la Terre. La derni\u00e8re glaciation s'est termin\u00e9e il y a un peu moins de 20 000 ans. Nous traversons actuellement une p\u00e9riode interglaciaire mais la modification de la\u2026","rel":"","context":"Dans &quot;Arch\u00e9ologie&quot;","block_context":{"text":"Arch\u00e9ologie","link":"https:\/\/www.laterredufutur.com\/accueil\/sujets\/archeologie\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.laterredufutur.com\/accueil\/wp-content\/uploads\/2015\/12\/glaciers-climat.png?fit=576%2C384&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.laterredufutur.com\/accueil\/wp-content\/uploads\/2015\/12\/glaciers-climat.png?fit=576%2C384&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/www.laterredufutur.com\/accueil\/wp-content\/uploads\/2015\/12\/glaciers-climat.png?fit=576%2C384&ssl=1&resize=525%2C300 1.5x"},"classes":[]}],"jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.laterredufutur.com\/accueil\/wp-json\/wp\/v2\/posts\/4720","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.laterredufutur.com\/accueil\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.laterredufutur.com\/accueil\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.laterredufutur.com\/accueil\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.laterredufutur.com\/accueil\/wp-json\/wp\/v2\/comments?post=4720"}],"version-history":[{"count":1,"href":"https:\/\/www.laterredufutur.com\/accueil\/wp-json\/wp\/v2\/posts\/4720\/revisions"}],"predecessor-version":[{"id":4722,"href":"https:\/\/www.laterredufutur.com\/accueil\/wp-json\/wp\/v2\/posts\/4720\/revisions\/4722"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.laterredufutur.com\/accueil\/wp-json\/wp\/v2\/media\/4721"}],"wp:attachment":[{"href":"https:\/\/www.laterredufutur.com\/accueil\/wp-json\/wp\/v2\/media?parent=4720"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.laterredufutur.com\/accueil\/wp-json\/wp\/v2\/categories?post=4720"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.laterredufutur.com\/accueil\/wp-json\/wp\/v2\/tags?post=4720"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}