“When a volcano erupts beneath the sea, super-hot lava gushes out, just like you might see on land”
ENVIRONMENT
Submarine volcanoes Our planet’s most productive volcanic activity happens at the crushing depths of ocean ridges
Erupting under the sea What goes on in the water and beneath the seabed as magma bubbles up from below
Mineral deposits
Black or white smoke
These mineral deposits help to build he chimneys into tall, towering stacks.
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.
illow lava The underwater eruption forms illow lava, formed as the outer layers of lava harden as it meets the seawater.
Seawater Cool seawater enters cracks in the rocks and filters deep down into the Earth.
Volcanic chains Not all submarine volcanoes are located at tectonic Heated from below boundaries. Long, linear chains of volcanoes such The magma heats up the as the Hawaiian Islands and their underwater water as it trickles neighbours can form in the middle of oceanic through the rock. basins. This is a by-product of continental drift – the gradual movement of tectonic plates. As the plate rests over a magma plume (an intense Minerals dissolved build-up of magma beneath the Earth’s crust, The water becomes more sometimes known as a ‘hotspot’) the magma acidic as it warms, and it pushes its way up to the surface and a volcano will dissolves minerals from form, a process that takes thousands of years. The the surrounding rock. volcano may even stay active long enough to breach the ocean surface, forming an island. Then as the continental plate moves on, taking the 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 The Hawaiian Islands are chain get older the further they part of a chain of volcanoes extend from the magma plume.
recipitating minerals the vent fluid mixes with ld seawater, it causes some the dissolved minerals to ecipitate as fine particles.
Through the vents The heated fluid 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.
formed over a hotspot
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© Science Photo Library; Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC
The boundaries of Earth’s tectonic plates are areas of pure fire and brimstone! Where the plates rub up against one another, or pull apart from each other, the super-heated innards of our planet are waiting to spill out, and this is where volcanoes can be found. An underwater volcano forms when magma – molten rock from underneath the Earth’s crust – builds up in a deep chamber. As the pressure increases, the magma finds its way upward until it reaches the seabed and the pressure is released in the form of a gigantic lava flow. When a volcano erupts beneath the sea, super-hot lava gushes out, just like you might see on land. In relatively shallow water, this can send a spray of rocks, ash and gas through the water and out into the air. Deep-sea volcanoes are under crushing pressure from the water above, but the sheer force of the eruption still sends lava out of the fissure. Lava that oozes out is quenched almost as soon as it hits the water, and so the most common type of lava flow from an underwater volcano is ‘pillow lava’. The outside of the lava flow hardens, but the inside stays molten, breaking through the end of the quenched blob and splurging forward – building up a string of pillow shapes before hardening to solid rock. These eruptions build layer upon layer of rock, and this i6s how the volcano grows in size.
