Describe underwater volcanoes?

Question

How do they react to being that deep underwater? What do they look like? 10 points to anyone who can give me a well-thought out answer.

Answer 1

There are two important factors that affects the characteristic of submarine volcanism that usually are coupled together. This are the tectonic setting and the depth of water above the volcano.

Water produces rapid cooling of the surface of the lava and high pressure that prevents the rapid loss of volatiles.

In mid ocean ridges (usually very deep, but with important exceptions) you almost have not true volcanoes and are more fissural effussions of basaltic magma. Here it is common the presence of pillow lavas with chilled margins that correspond mostly to glass (quenched magma), but you also have sheeted flows that are the equivalents of pahoehoe lava flows (typical of Hawaii). They may form extensive areas of thin magma that can flow for miles until a depression is found filling up the depression with a thick layer of lava that in this case travel off axis and it is called an inflated flow.

Another important tectonic setting is island arc, where you have a young subduction zone forming submarine volcanism. The magma here is andesitic to dacitic and in some cases rhyolitic. The magma here is more viscous and is charged with volcanic gasses (mostly water). The depth here varies a lot and evolve with time and plays a major role in the volcanic style of the eruptions. At first you have pillow lavas, but then dacitic magma is viscous and will not flow as basaltic magma and form domes instead and here is common the formation of hyaloclastites which are a strongly fragmented rock (a breccia) of fast quenched magma formed mostly by glass. As the volcano grows (here you can really talk about volcanoes), the water column is progressively less and in some cases you can have submarine pyroclastic deposits that where previously prevented to form due to the pressure exerted by the water. This critical point defines the beginning of explosive volcanism. Water can contribute to form freatomagmatic eruptions, etc. The presence of pillow lavas in this setting is rare but hyaloclastites are common as well as some peperites. When the volcanism stops hydrothermal fluids may produce massive sulfide deposits. This is the typical setting for massive sulfide deposits, in which usually the depth is enough to prevent boiling of the hydrothermal fluid until it reaches the sea-floor. Even though there are black smokers (rich in sulfides) in Mid-Ocean ridges, there are not known massive sulfides deposits associated to it.

Hot spots or Hawaiian type tectonic setting is similar to Mid Ocean ridge basalts but more localized forming true shield volcanoes. You may have locally the formation of hyaloclastites but pillow lavas are common.

Answer 2

Underwater volcanoes have a few differences to surficial volcanoes. Firstly, pillow basalts are a common result of them. These are rounded, bloby lava bodies formed when water cools a 'shell' around a lava, then as more lava flows, the lava squirts out to form another 'pillow' shaped body. On a hand sample to microscopic level, you get what are called chilled margins; extremely small crystals that instantly freeze in the water.

Most undersea volcaoes are from mid-ocean ridges, which are long linear bodies of volcaoes where new oceanic crust is formed. They look like a normal volcano, except for the faulted center, which instead of a crater, you get a graben. Subduction and hot spot activity can form volcanoes underwater, but they usually build up eventually and form an island, so it is temporary. There is a famous one forming off the coast of the big island of Hawaii... it will be the next Hawaiian island in a million years!

Answer 3

Underwater volcano are just like any other volcano on the surface. They can explode just the same. Not too long ago there was one on CNN news displaying a volcano under water that was gushing out lava which created much steam.

Answer 4

Ok.... Picture a Volcano. You got that one in your head?

Now.... Picture a Lot of water......

Now put the two images together.

BAM! Underwater frikkin Volcano!

Answer 5

well they're the same as the volcanoes on land except when they erupt it's into water which cools down the spew quickly. since they have loads of pressure on them they dont' erupt as frequently, but that depends on the plates