[00:00.00]So, we've talked about the plates that form the earth crust and their movements and how in some places they're separating. [00:13.55]Now, when this happens in the ocean along a mid ocean ridge, some important things can happen, in particular you can get a hydrothermal vent. [00:25.28]This is a lot like a geyser except it’s on the ocean floor.
[00:29.44]A geyser, of course, is a kind of eruption from underground hot spring. [00:35.31]Water that’s been heated up in Earth’s interior, when under pressure, can erupt, sending that water and steam, shooting upwards through crack in the earth. [00:47.07]A hydrothermal vent is essentially this same thing, but the water is emitted out of cracks or, or fractures in the ocean floor. [00:57.92]If [01:10.04]Forms that don't depend on energy from the sun, but depend on chemical energy.
[01:16.19]But, the vents are also enormous significance for us. [01:20.54]From a purely geological perspective, because the chemistry of the oceans is affected by them. [01:28.82]To see how, let’s look at the process a little more closely. [01:33.64]They typically occur in fields, so you might have an area with a dozen of them, but you need two things to get one of these fields, first, you gotta have heat. [01:47.00]And you’ve gotta have fissures in the ocean floor. [01:50.94]So, in a vent field, you've got cracks in the ocean floor. [01:55.92]And cold water at the bottom of the ocean, we are talking, maybe two degrees Celsius, goes down into them, as it goes underground, it heats up, because in these fields, there are magma chambers, only a few kilometers below the ocean floor.
[02:13.86]This hot molten rock heats the solid rock above it to as high as five hundred degrees Celsius. [02:21.51]And this heated solid rock, then heats the ocean water that flows over it. [02:27.74]Now remember, the high pressure of the deep sea, allows water to stay liquid at such a high temperature, so it can reach temperatures of, three or four hundred degrees Celsius.
[02:41.03]As the water heated, it rises up through other cracks and it shoots up back into the ocean, much like with geyser on land. [02:51.47]Now, the important part, is what the water is carrying with it, as it emerges. [02:57.76]The heated water draws minerals from solid rock. So, you get dissolved metals in the water, like iron and copper. [03:07.60]When the water shoots up and re-enters the cold ocean, it quickly cools and these minerals precipitate out. [03:16.57]They’re released and they are deposited into the ocean water, which affects its composition. [03:23.35]And it also creates quite a site, these vents have a plume that looks like a smoke, likes smoke that’s coming up out of the vent in the earth.
[03:35.14]Remember some of the water coming out of the vents is over three hundred degree Celsius. [03:41.74]When it’s this hot, it dissolves sulfur, iron and other metals in the rock and it interacts with. [03:49.31]when these minerals precipitate out, the water forms of black plume, so these vents are called black smokers. [03:59.78]It's the sulfur and metals precipitating out of the water that that's what causes black color.
[04:07.38]But there are also white smokers, these emit what looks like a white smoke. [04:14.29]That's because their water is relatively cool, above one hundred to three hundred degrees. [04:20.48]Still pretty warm, but, not warm enough to dissolve sulfur or iron. [04:25.64]Instead, they draw off different minerals from rocks. Things like silica and they give off different color, whitish color, when those minerals precipitate out.
[04:38.13]But in both black and white smokers as the waters emitted in the plume, the mineral that precipitate out, eventually build up around the vent, forming large, tower, like structures or minerals, build up layer upon layer, we call these chimneys, just like a chimney on a house. [05:01.22] Different minerals will tend to build up at different places on the chimneys. [05:05.85]But, some of the minerals like silica, a form kind of cement, and they hold the whole structure together. [05:14.37]So, they can grow quite large and quite quickly. [05:18.81]If you can believe it there was one chimney that reached forty-seven meters, that’s like fourteen story [05:27.36]It collapsed, but it’s actually now rebuilding.
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