Many of the worlds islands were formed by this process, releasing thousands of tons of salt in the process. Magma erupting through submarine fissures boils the surrounding water, which then dissolves salts in the cooling rock to escape in a manner similar to hydrothermal vents. Submarine volcanoes are comparable to their above-ground relatives except that their lava cools much more rapidly, allowing for speedy growth. ![]() The water is superheated from magma below, and as it travels up it dissolves minerals locked in the crust, erupting as mineral-rich steam.Ī similar process involves the interaction of submarine volcanoes with surrounding seawater. Hydrothermal vents allow seawater that has seeped though the rock of the oceanic crust to return to the surface. Ongoing volcanism still has an important role to play. When an organism dies and decomposes, the salt is freed to continue its seaward journey.Īcid rain isn’t the only way the seas are fed with salt. Salt is crucial to both plant and animal life, regulating the amount of fluid in cells and neuron function. The process continues.Īlong the way from rock to sea, a fair proportion of the salt released from rock is used by living things. Although the amount deposited by any one outlet was small, the contribution of millions of outlets over millions of years gradually raised the salinity of the oceans. The runoff slowly carried the salt to nearby lakes and rivers, which in turn carried it to the seas. This carbonic acid rained down on salt-rich rock, slowly breaking through and releasing the trapped salt into rainwater. ![]() When mixed with water (H 2O), carbon dioxide (CO 2) can form carbonic acid (H 2CO 3), a weak but corrosive acid. ![]() It came from rock, laden with elemental salts including sodium, chlorine and potassium, that was spewed forth as magmatic material by massive volcanos from the depths of the planet.Įnter erosion, the process liberating these salts from their rocky prison, thanks to an atmosphere dominated by gases including nitrogen and, importantly, carbon dioxide. But seawater wasn’t always so salty when the Earth’s oceans first formed about 3.8 billion years ago, as the surface of the planet cooled enough to allow water vapour to liquify, the oceans were mostly fresh water. It is estimated there is enough salt in the world’s oceans to cover all the planet’s land surfaces with a layer about 40 stories thick.
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