Our Beautiful World

Submarine volcanoes

White chimneys at Champagne vent site, NW Eifuku volcano, Mariana Arc, Pacific Ocean.
The chimneys are ~20 cm (8 in) across and ~50 cmhigh, venting fluids at 103ºC (217ºF).

Submarine volcanoes do not have the same interest to media as volcanoes on land.
One reason is because there normally are not any large cities beneath such a volcano....
(at least, not to our knowledge), and therefore no threat to humans.

That they are not dangerous because they are under the sea-level is not true.
After having learned about "Kick 'em Jenny", we am sure you agree.

This is the first time that glowing lava has ever been witnessed from a submarine
volcanic eruption! In this case, the lava is rising in the vent so fast that a small
glimpse of red glow can be seen intermittently before it crusts over or is blown apart.
What a sight! Do you think the scientists were a little excited? The Jason ROV is
operated by Woods Hole Oceanographic Institution as part of the National Deep Submergence Facility which is jointly funded by the National Science Foundation,
the Office of Naval Research and the National Oceanographic and Atmospheric
Video courtesy of Submarine Ring of Fire 2006 Exploration, NOAA Vents Program.
Uploaded by oceanexplorergov on Dec 11, 2006

So, since submarine volcanoes also are volcanoes, but in a way sometimes
even more interesting, we will try to introduce them to you here.
Of course, there are lots of other web-pages on the net, and the sub-volcanoes
even have their own fans, so doing a little surfing on the net will surely give results.

Barren Island Jack Panarea
Bayonnaise Kavachi Rumble III
El Hierro Kick 'em Jenny Fukutoku-Okanoba
Ferdinandea / Graham Kolumbo Scotia Sea
Gakkel Ridge  Mariana Arc Terceira
Gorda Ridge Marsili Vailulu'u
Cayman Ridge, Caribbean Ashadze-1, Mid Atlantic Ridge  

The volcanoes of Tonga.
18 different volcanoes ashore and under sea-surface described.

Submarine volcanoes are found along the most fissures between the techtonic plates. Many of those
submarine volcanoes developes over so called hot spots.

The most important volcanic activity, is in fact the one going on down below in the oceans.
One ridge going from North of Jan Mayen (north of Norway) via Iceland, Azores, Aschencion,
Tristan da Cunhan, and down to Bouvet-Island in the south Atlantic Ocean. From there it turns
toward the Indian Ocean, then south of Australia and across the Pacific Ocean. This ridge has a total length
of 60.000 km, or one and a half times around the globe if you could stretch it out.

This ridge makes an undersea mountainridge from 1.000 to 2.000 km width, and 1.000 to 3.000 meter above
the botton of the ocean. Along the middle is a riftzone from 20 to 50 km width. This again is between 500 to
1.500 m deep, and follows the ridge all around the globe. The rift itselv is more like a valley, from 5 to
10 km wide, and it is where the volcanic activity happens.

From time to time fissures opens up within the valley, some kilometer long and some few meters wide.
Those are soon filled up by lava from down below.

Some openings are on relatively shallow water, and gas and pumice
flows up to the surface. Under extreme conditions, those eruptions may develope into tsunamis with devasting results. In other cases they can make new islands to show ujp, like Surtsey outside Iceland..

The scientific team attributed their seismic observations coupled with the floating blocks to the following
mechanism. The magma, being low in viscosity, moves very easily through the already opened fractures
and was thought to escape without producing high seismic signals. Floating lava blocks could result from
the detachment of pillow-lava edges followed by the ascent of blocks with sufficient gas content.
It is also possible that hot, gas-rich lava fragments result from small submarine lava lakes or fountains.
A thin frozen skin of lava seals the gas cavity, and the block might then rise as a hot lava balloon.
During ascent, the gas exsolves and nucleates inside the hot fragment while the blocks expand.
Once at the surface the interaction between the hot blocks and the seawater produces white steam columns.
At the same time, while cooling at the surface, the blocks crack slowly, lose their magmatic gas and sink.
Sometimes when water enters inside the hot blocks, they blow up, violently throwing fragments several
meters high.

Schematic presentation of the 1999 Azores events at Forjaz -
image courtesy geocrusoe.blogspot.com

Se Terceira and El Hierro submarine volcanoes.


In deep waters, more than 2000 m, the pressure is often so high that in stops the effusion of gas and vapour,
and this activity is seldom seen from above the surface. The pressure is so high that water does not boil (cook),
but changes to vapour when the temperature exceeds 350 - 400°C.
See how this was true during the El Hierro eruption late 2010.

On the Loihi mountain range south of Big Island, Hawaii, a new volcano was recently discovered.
The top of Loihi is 3.000 meter above seabottom, and the new top only about 1.000 meter
below the ocean surface. It has a crater of 5 km width. Flows of lava has been photographed by
means of submarine cameras. Probably is this volcano only some few hundred years old,
and quakes in the area around 1971, 1975 og 1985 are probably results of magma being filled
up in the upper chambers of the volcano.

See also Marsili-volcano which recently showed up in the Mediterraneas Sea.


Deep-sea hydrothermal vents
Since the first discovery of deep-sea hydrothermal vents along the Gala´pagos Rift in 1977, numerous vent sites and endemic
faunal assemblages have been found along mid-ocean ridges and back-arc basins at low to mid latitudes. These discoveries
have suggested the existence of separate biogeographic provinces in the Atlantic and the North West Pacific, the existence
of a province including the South West Pacific and Indian Ocean, and a separation of the North East Pacific, North East
Pacific Rise, and South East Pacific Rise. The Southern Ocean is known to be a region of high deep-sea species diversity and
centre of origin for the global deep-sea fauna. It has also been proposed as a gateway connecting hydrothermal vents in
different oceans but is little explored because of extreme conditions.

We will try to follow up those new discoveries.
The last one is from the Scotia-sea area. Click here to follow up.

 Submarine Volcanoes, Ridges, and Vents,  from USGS


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