Submarinevolcanoes

ENVIRONMENT

“ When a volcano erupts beneath the sea, super-hot lava gushes out, just like you might see on land”

Submarine volcanoes

Our planet’s most productive volcanic activity happens at the crushing depths of ocean ridges

TheboundariesofEarth’stectonicplates are areas of pure fire and brimstone! Where the plates rub up againstone another, or pull apart from each other,the super-heated innards of our planet arewaitingto spill out, and this is where volcanoes canbefound.

An underwater volcano forms when magma–molten rock from underneath the Earth’scrust–builds up in a deep chamber. As the pressure increases, the magma finds its way upwarduntilit reaches the seabed and the pressure is releasedin the form of a gigantic lava flow.

When a volcano erupts beneath the sea, super-hot lava gushes out, just like youmightsee on land. In relatively shallow water, thiscansenda spray of rocks, ash and gas through thewaterand out into the air. Deep-sea volcanoes areunder crushing pressure from the water above,butthe sheer force of the eruption still sends lavaoutofthe fissure. Lava that oozes out is quenchedalmostas soon as it hits the water, and so the mostcommon type of lava flow from an underwater volcanois ‘pillow lava’. The outside of the lava flowhardens, but the inside stays molten, breaking throughthe end of the quenched blob and splurgingforward–building up a string of pillow shapes before hardening to solid rock. These eruptionsbuild layer upon layer of rock, and this i6s howthe volcanogrowsinsize.

Erupting under the sea

What goes on in the water and beneath the seabed as magmabubblesupfrombelow

Black or white smoke

These precipitates are what give the vents a ‘smokey’ appearance. Black or white smoke is caused by different mineral content.

Eruption

When the volcano erupts, lava that can reach 1,200°C (2,200°F) is expelled from the volcano’s crater.

Seawater

Coolseawaterenters cracksintherocks andfiltersdeepdown intotheEarth.

Mineral deposits

These mineral deposits help to build he chimneys into tall, towering stacks.

illow lava

The underwater eruption forms illow lava, formed as the outer layers of lava harden as it meets the seawater.

Volcanic chains

Not all submarine volcanoes are locatedattectonic boundaries. Long, linear chains of volcanoessuch as the Hawaiian Islands and their underwater neighbours can form in the middle of oceanic basins. This is a by-product of continentaldrift–the gradual movement of tectonic plates.Asthe plate rests over a magma plume (an intense build-up of magma beneath the Earth’scrust, sometimes known as a ‘hotspot’) the magma pushes its way up to the surface and a volcanowill form, a process that takes thousands ofyears.The volcano may even stay active long enoughto breach the ocean surface, forminganisland.Then as the continental plate moves on,takingthe volcano with it, a brand-new volcano eventually forms on the part of the continental crust that is now positioned over the magma plume. This means the volcanoes in the chain get older the further they extend from the magma plume.

Heatedfrombelow

Themagmaheatsupthe waterasittrickles throughtherock.

Minerals dissolved

The water becomes more acidic as it warms, and it dissolves minerals from the surrounding rock.

The HawaiianIslandsare part of a chainofvolcanoes formedoverahotspot

recipitating minerals

the vent fl uid mixes with ld seawater, it causes some the dissolved minerals to ecipitate as fi ne particles.

Through the vents

The heated fl uid rises and is eventually expelled by the large vents that accompany submarine volcanoes.

Magma chamber

The volcano’s magma chamber is stored many kilometres below the seabed.