{"id":39094,"date":"2022-06-15T00:01:48","date_gmt":"2022-06-15T07:01:48","guid":{"rendered":"https:\/\/hakaimagazine.com\/?post_type=custom_news&p=39094"},"modified":"2022-06-15T09:22:14","modified_gmt":"2022-06-15T16:22:14","slug":"how-the-ocean-inside-the-mantle-affects-the-habitability-of-the-earth","status":"publish","type":"custom_news","link":"https:\/\/hakaimagazine.com\/news\/how-the-ocean-inside-the-mantle-affects-the-habitability-of-the-earth\/","title":{"rendered":"How the Ocean Inside the Mantle Affects the Habitability of the Earth"},"content":{"rendered":"

Hidden inside the Earth\u2014within the first several hundred kilometers below the crust\u2014there is another ocean. It is, most likely, the largest ocean in the world<\/a>. This water is not sloshing around in a big pool. No fish plumb its depths. In fact, this ocean is only water in the loosest sense: broken into its composite hydrogen and oxygen atoms and chemically bound to the surrounding rock, this ocean is in storage. Or, most of it is.<\/p>\n

Denis Andrault and Nathalie Bolfan-Casanova, geoscientists at the University of Clermont Auvergne in France, have developed a new model that shows more of this water is in transit than previously thought<\/a>. When the solid rock in the mantle\u2014the layer of the planet between the crust and the core\u2014becomes saturated with chemically dissociated water, it can transform into a water-rich molten slurry. When it does, it seeps back up toward the crust. The researchers call this mantle rain.<\/p>\n

Much as the cycling of water between the atmosphere, glaciers, lakes, rivers, aquifers, and the ocean affects the level of the sea, the abundance of rain, and the frequency of drought, the exchange of water between the mantle and the surface also dictates the habitability of the Earth. Scientists already know that water can be dragged down to the mantle by subducting tectonic plates and brought back to the surface by things like volcanic eruptions, hydrothermal vents, and the creation of new crust at oceanic spreading centers. If this deep water cycle between the mantle and the surface is in balance, Earth\u2019s sea level remains stable. If not, our planet could exist as anything from a singular global ocean to a desiccated world.<\/p>\n

Earth\u2019s habitability has benefited greatly from the fact that Earth\u2019s sea levels have remained relatively<\/em> stable over billions of years. According to previous studies of the mantle, however, it could have been very different. Estimates based on previously understood mechanics of the deep water cycle suggest that nearly twice as much water is carried into the mantle as is released back to the surface.<\/p>\n

\u201cThere is a layer about 410 kilometers below the surface that can hold a lot of water,\u201d says Andrault. The prevailing understanding says that water should stay there forever, he says. If that were the case, the Earth\u2019s surface water would have slowly decreased, locked away in the mantle.<\/p>\n

But that\u2019s where mantle rain comes in.<\/p>\n

In their study, Andrault and Bolfan-Casanova show that mantle rain could be enough to keep the deep water cycle in balance.<\/p>\n

To discover mantle rain, the researchers looked at what happens when a subducting slab of rock and rock-bound water sinks deeper into the mantle. They found that as it descends, increasing temperatures and pressures cause the rocks to melt, releasing the water.<\/p>\n

\u201cThe melt is like a slurry,\u201d says Andrault. \u201cImagine a mushy mix of sand grains glued to each other with mud in between\u2014the mud is the mantle rain.\u201d<\/p>\n

As more rocks melt, and as more water is liberated from the rock, this melt eventually becomes light enough that it begins to rise. As it does, the water bonds to minerals in the upper mantle and lowers their melting points, causing more melting that releases more water\u2014and the cycle continues.<\/p>\n

Andrault and Bolfan-Casanova\u2019s model of mantle rain, says Yoshinori Miyazaki, an earth and planetary scientist at the California Institute of Technology who was not involved in the study, \u201cshows there could be another way to transport water towards the surface in addition to the global-scale convection of the mantle itself.\u201d<\/p>\n

\u201cWater generally doesn\u2019t like to be in the rock phase,\u201d Miyazaki says. \u201cIt will happily escape to the melt phase and percolate upwards.\u201d Andrault says more work is needed to understand the extent to which water is escaping in this way.<\/p>\n

The mantle rain model also suggests that there is currently one ocean mass in the upper mantle. \u201cTogether with the ocean on the surface,\u201d says Andrault, \u201cthis ensures that there will always be water on Earth\u2019s surface.\u201d<\/p>\n

\u201cWe still have a lot to learn about the deep water cycle,\u201d says Miyazaki. \u201cBut one certain fact is that it has worked in an amazing way to keep Earth\u2019s average sea level relatively constant over the past 500 million years, and probably longer, to sustain a habitable environment for life to continue.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"

Hidden inside the Earth\u2014within the first several hundred kilometers below the crust\u2014there is another ocean. It is, most likely, the largest ocean in the world. This water is not sloshing around in a big pool. No fish plumb its depths. <\/p>\n

…<\/span><\/div>\n","protected":false},"featured_media":39096,"menu_order":0,"template":"","format":"standard","meta":{"_acf_changed":false,"om_disable_all_campaigns":false,"footnotes":""},"categories":[201],"tags":[],"acf":{"hero_video_url":null,"hero_video_caption":"","deck":"A new model suggests \u201cmantle rain\u201d from inside Earth\u2019s mantle ensures we will always have a surface ocean.","authors_group":[{"by_group":"by","contributors_group":[35408]}],"word_count_override":"","podbean1":"","podbean2":"","redirect":"","geolocation":null,"related":[22749,17141],"twitterimage":39097,"facebookimage":39095,"twitterdescription":"","edited":[15491],"factchecked":"","code":"","no_old_story_flag":""},"_links":{"self":[{"href":"https:\/\/hakaimagazine.com\/wp-json\/wp\/v2\/news\/39094"}],"collection":[{"href":"https:\/\/hakaimagazine.com\/wp-json\/wp\/v2\/news"}],"about":[{"href":"https:\/\/hakaimagazine.com\/wp-json\/wp\/v2\/types\/custom_news"}],"version-history":[{"count":4,"href":"https:\/\/hakaimagazine.com\/wp-json\/wp\/v2\/news\/39094\/revisions"}],"predecessor-version":[{"id":39107,"href":"https:\/\/hakaimagazine.com\/wp-json\/wp\/v2\/news\/39094\/revisions\/39107"}],"acf:post":[{"embeddable":true,"href":"https:\/\/hakaimagazine.com\/wp-json\/wp\/v2\/profiles\/15491"},{"embeddable":true,"href":"https:\/\/hakaimagazine.com\/wp-json\/wp\/v2\/news\/17141"},{"embeddable":true,"href":"https:\/\/hakaimagazine.com\/wp-json\/wp\/v2\/news\/22749"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/hakaimagazine.com\/wp-json\/wp\/v2\/media\/39096"}],"wp:attachment":[{"href":"https:\/\/hakaimagazine.com\/wp-json\/wp\/v2\/media?parent=39094"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/hakaimagazine.com\/wp-json\/wp\/v2\/categories?post=39094"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/hakaimagazine.com\/wp-json\/wp\/v2\/tags?post=39094"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}