Submarine Volcanoes

There are islands made entirely from volcanic material.

They are the opera of submarine volcanoes.

But even today, this phenomenon can be seen, like in Tonga archipelago.

More than 1,000,000 submarine volcanoes are estimated by scientists.

There are underwater fissures in the earth's surface from which magma can sip out.

75,000 submarine volcanoes rise about 1 km (0.6 miles) above the ocean's floor.

75 % of the annual magma output is spitted by submarine volcanoes.

Normally, they form chains of volcanoes along the oceanic rifts, like the Mid-Atlantic Ridge at about 2500 m depth, but they sometimes emerge on ground, like in Iceland, island located on the rift that splits in two the bottom of the Atlantic Ocean.

They are also abundant on Pacific's Ring of Fire.

But these submarine wells were also found at 6,000 m (3.5 miles) depth at the zone were the Pacific plaque is subducted under the Eurasian plaque, near Japan.

Some submarine volcanoes also occur in shallow water and can spew material into the air during an eruption, like in the case of Tonga.

Submarine volcanoes are normally accompanied by hydrothermal vents.

In the Atlantic rift, on a width of 50-100 m, hot vents with temperatures between 150 - 500 degrees C are associated with deposits of polymetallic sulfides (of copper, zinc, iron, and others), pyramidal columns of stratified lava and a peculiar fauna.

The water is shot at 70 km (40 miles) per hour.

The unusual fauna is found both around the volcanoes and the vents, which provide heat and chemicals for their existence.

Unlike the normal biological ecosystems, which are fed by the food made by plants using sunlight, these ecosystems are based on the activity of specific bacteria, that through chemosynthesis make food oxidizing the sulfur and its compounds.

On these bacteria are dependent many crabs, tube worms, clams, mussels, echinoderms and even some fish species.

The cold water modifies the volcanic eruption as we know it.

The higher thermal conductivity of water turns the magma into glass much more quickly than in a terrestrial eruption.

Also, some submarine volcanoes are located at depths where the underwater pressure can reach over 250 atmospheres, fact that greatly decreases the explosive reaction between magma and seawater.

Because they are so quiet, deep-sea volcanoes are extremely difficult to detect.

The hot magma in contact with the cold seawater forms a solid crust and advancing lava flows into this crust, generating the so-called pillow lavas (photo).

This magma forms the edges of the new oceanic plates.

Each year 200 cubic km of rocks rejuvenate Earth's crust.

A similar amount disappears on the oceanic fosses.

The Kolumbo underwater volcano in the Aegean Sea was discovered in 1650 when it burst from the sea and erupted, killing 70 people on the nearby island of Santorini.