Earth’s water and volcanoes: a closely related story

In that world water dayDid you know that this element, so valuable for life, in abundance on our beautiful blue planet, is partly of volcanic origin? This is actually partly due to the outgassing of volcanoes since the formation of the Earth, which has gradually shaped the atmosphere and hydrosphere we know. Today, the waters of the oceans cover many volcanoes: deep volcanoes, unknown and invisible, and others close to the surface, the eruptions of which are explosive in nature …

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That gas that make up our planet’s atmosphere probably come from two different processes, with proportions which is inappropriate to discuss here. And if the release of gases present in asteroids that affect the surface Earth at the beginning of its history is a long-gone process, degassing The volcano is still going on at the present time! Volcanic activity has certainly decreased significantly compared to the first moments of the existence of our planet, but each active volcano releases a different amount of gas that accumulates in our atmosphere. However, water is one of the gases emitted in very large quantities. IN Python from Fournaise For example, water is 65% of emitted gases. On theEtnait would even over 85% !

Then this primitive atmosphere cooled down, allowing condensation this water vapor, thus forming first oceans. Today they cover about two-thirds of the globe and, inevitably, some volcanoes

The contact of lava with water is often effusive, but not always…

In general, the relief of the seabed of our oceans is not known exactly enough, therefore, the volcanoes that exist there are mostly unknown, even if we know that they exist! And not without reason the majority volcanism earthly ones are concentrated where tectonic plates deviate and, with a few exceptions, Iceland or in Ethiopia in particular, these places are in the middle of the oceans and at great depths. These mid-ocean waves draw a giant chain of seamounts stretching nearly 60 to 80,000 kilometers and culminating between 2,000 and 2,500 meters below the surface of the ocean. At this depth pressure is such that the magmatic gases are compressed: eruptions are therefore effusiveso that when the boat passes overhead, nothing is noticed!

At the level of these ocean ridgescontinuous separation of tectonic plates does not allow lava to accumulate and form large structures, unlike volcanoes subduction or from access point. In these geodynamic conditions, the proposal magma actually located in the same place over time, which allows the construction of imposing buildings. Over time, the top of the volcano can come close to the surface of the ocean. However, the pressure decreases with depth, so that at a depth of several tens of meters the water pressure is no longer sufficient to compress the gases. As a result, seawater heated by lava can evaporate, adding gas to the magma. However, this evaporation accompanied by a significant increase volume and this is in rough form: the contact between lava and water at a shallow depth is therefore very explosive! This causes the so-called eruptions. Surtseyennewith respect to the Icelandic island Surtsey was born in 1963 thanks to this type of dynamism.

Phreatomagmatic eruptions also occasionally occur duringvolcanic eruptions on land when lava meets ice ice capriver water, lake water or ground water level in the depths. Because yes, volcanic structures often contain aquifersthat makes the reputation of these drinking waters! Another example, if needed, is that volcanoes are also sources of life!

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