\n
![\"EarthSnap\"\/](\"https:\/\/www.newsbeep.com\/ie\/wp-content\/uploads\/2025\/09\/earthsnap-banner-news.webp.webp\")
\n<\/a><\/p>\n
One region in the North Atlantic has always been harder to explain. Its crust is several times thicker than expected, and its lavas contain more water than a mantle plume should provide. <\/p>\n
A new study argues the answer may not lie in heat at all, but in a cold relic left behind by an ancient ocean.<\/p>\n
A volcano puzzle<\/p>\n
That anomaly is the Azores Plateau, a broad rise in the North Atlantic dotted with nine volcanic<\/a> islands. <\/p>\n Normal ocean crust is about four miles thick. Here it swells to as much as 19 miles. For thick crust like this, the textbook answer has always been a mantle plume. <\/p>\n Hawaii and Iceland are the standard examples. The Azores have never been a clean fit.<\/p>\n Dr. Jianfeng Yang at the Chinese Academy of Sciences (CAS<\/a>) in Beijing led a team that was puzzled by the misfit. <\/p>\n They tested the idea using simulations of mantle flow and melting. The simulations suggested that a mantle plume alone could not account for the observations.<\/p>\n Water from below<\/p>\n The trail leads to the transition zone, a layer of mantle rock<\/a> roughly 250 to 400 miles below the surface, where minerals hold a lot of water. <\/p>\n A diamond carried up from there proved it, holding a water-rich grain. One study<\/a> showed that deep Earth is anything but dry.<\/p>\n Water reaches such depths through subduction, the slow process where one plate slides beneath another and sinks into the mantle. <\/p>\n The descending slab hauls water-soaked rock down. Much gets wrung out near the surface, but some rides into the transition zone and stays.<\/p>\n Those sinking slabs are old ocean floors, plates that finished their life and slid into the depths. <\/p>\n Over hundreds of millions of years, their cargo of water collects in pockets of the transition zone. One review<\/a> of the deep water cycle describes that transport system in detail.<\/p>\n Running the models<\/p>\n In the simulations, the team set a mid-ocean ridge drifting across the seafloor. Beneath it sat mantle rock containing a few tenths of a percent water. Then they let the physics<\/a> run.<\/p>\n Water changes how rock behaves. Even a trace lets mantle rock melt at lower temperatures than dry rock could. <\/p>\n As the ridge wandered over the damp patch, that wet material welled upward and began to melt. It produced far more magma than comparable dry rock.<\/p>\n A fixed hot spot would tap one spot until it ran dry, but a moving ridge kept sliding into fresh, wet mantle<\/a>, feeding eruption after eruption. <\/p>\n The drifting was the engine. These are merely model results and only a proposed mechanism, not a snapshot of the seafloor.<\/p>\n Building thick crust<\/p>\n In the models, that long bout of melting built oceanic crust between six and 12 miles thick, several times the ocean norm and squarely in the range measured under the Azores. <\/p>\n The mechanism reproduced features that plume models had struggled to explain. The melting tracked a moving ridge instead of a fixed point. <\/p>\n Because of this, eruptions were spread across a broader region rather than concentrated into a single volcanic chain. <\/p>\n Because the source rock in the model was damp, the lavas carried the wet fingerprint real Azores rocks show.<\/p>\n Researchers already knew the deep Earth holds water, and that plumes can raise plateaus. <\/p>\n What no one had shown was a migrating ridge drawing that buried water up to build a thick crust on its own. In this scenario, water played the dominant role rather than heat<\/a>.<\/p>\n A different engine<\/p>\n That flips the usual story for volcanoes erupting far away from any plate boundary. <\/p>\n Instead of unusually hot mantle rising from depth, the engine can be ancient water freed from the transition zone and tapped by a passing ridge. The plume is no longer the only suspect.<\/p>\n It also recasts those long-dead slabs as active players. Plates that sank into the mantle hundreds of millions of years ago may still influence volcanism at the surface, via the water they left behind. <\/p>\n That same logic may reach past one plateau. Broad stretches of deep rock carry odd chemical signatures that long puzzled geochemists, faint traces of surface material locked far below. <\/p>\n Recycled water rising from ancient slabs offers one possible explanation for those signatures, a possibility that one recent paper<\/a> keeps probing.<\/p>\n Indicating the future<\/p>\n Before this work, the thick crust and wet lavas of the Azores sat awkwardly inside a plume-only picture. Now there is an alternative. <\/p>\n The model suggests that water recycled from ancient plates, stored hundreds of miles below and drawn up by a wandering ridge, could build a plateau on its own.<\/p>\n That gives geologists a fresh lens for the many ocean plateaus and lone volcanoes that never sat neatly over a plume. Some may be wet-mantle features, not hot ones. <\/p>\n Mapping where ancient slabs stored water could help identify where similar volcanism may occur. It also tightens the bond between Earth\u2019s surface and its depths. <\/p>\n Water that once filled an ocean can vanish for ages, then return to help raise islands. The planet keeps a long memory, and traces of ancient oceans may still shape the surface today.<\/p>\n The study is published in Nature Communications<\/a>.<\/p>\n \u2014\u2013<\/p>\n Like what you read? Subscribe to our newsletter<\/a> for engaging articles, exclusive content, and the latest updates.<\/p>\n Check us out on EarthSnap<\/a>, a free app brought to you by Eric Ralls<\/a> and Earth.com.<\/p>\n \u2014\u2013<\/p>\n","protected":false},"excerpt":{"rendered":"When geologists find unusually thick oceanic crust, they usually reach for the same explanation. A mantle plume, which…\n","protected":false},"author":2,"featured_media":486898,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[61,60,82],"class_list":["post-486897","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-ie","tag-ireland","tag-science"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/486897","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/comments?post=486897"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/486897\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media\/486898"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media?parent=486897"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/categories?post=486897"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/tags?post=486897"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}