Picture of a hydrothermal vent, found at: http://commons.wikimedia.org/wiki/File:Explorer_Ridge_sulfide_chimney.jpg
Hydrothermal vents: giant vents at the bottom of the ocean that spew out incredibly hot, mineral rich water from beneath the crust of the Earth. I think they’re incredibly cool, and here’s why:
1. The geology of hydrothermal vents. The Earth is made up of plates of crust called tectonic plates, and these plates sit on top of a viscous layer of magma (molten rock), called the asthenosphere. Because the plates are separate and sit on this viscous layer, they can move, either drifting away from each other (divergent boundary), colliding into each other (convergent boundary), or sliding next to each other (transform boundary). So, when oceanic crust separates, it allows the magma, along with lots of other minerals that cycle through the Earth, to come up out of the Earth’s surface and cool into new crust.
Well, sometimes water seeps down near the magma through cracks in the Earth’s crust. This water mixes with lots of minerals underneath the Earth’s surface and then shoots back up in these hydrothermal vents.
2. The temperature changes. Because the hydrothermal vents are located at the bottom of the ocean, no sunlight reaches that far down, and therefore it is incredibly cold (around 2 degrees Celsius, almost freezing). However, where the hydrothermal vents spew water heated by magma, the waters get up to be around 400 degrees Celsius (to put this in perspective, 100 degrees Celsius is boiling). So, there’s water that’s 400 degrees Celsius, but go out a few feet and suddenly the water becomes 2 degrees Celsius.
3. The massive pressure. Hydrothermal vents are located at the deepest parts of our oceans, around two miles below the surface of the water. This creates massive pressure at the bottom of the ocean, accumulated from the tons of water sitting on top.
4. The fact that organisms actually live down there. It’s really incredible that organisms can live in an environment with such huge temperatures differences and intense pressure. But they do, and in fact thriving ecosystems have formed around these hydrothermal vents.
A picture of tubeworms near hydrothermal vents, found at: http://commons.wikimedia.org/wiki/File:Nur04507.jpg.
5. The Tubeworms. I put a picture of tubeworms above; these creatures are sessile and they are most commonly found near hydrothermal vents. They have no way of feeding and no digestive system, but instead in their tissues they have bacteria that live on the (to most creatures) toxic minerals that the hydrothermal vents spew out. The bacteria digest the toxic minerals and produce sugars and food for the worms inside of the worms. They get nutrition without ever having to eat, hunt down prey, or find food. Food is just inside of them.
6. The chemosynthesis. This is one of the only (if not the only) ecosystem on Earth that survives completely independently (for the most part) of the Sun.* On land, all energy comes from the Sun; the Sun produces light which plants turn into food by photosynthesis, then herbivores eat the plants, then carnivores eat the herbivores. However, in this specific ecosystem, the organisms get their energy from chemicals through chemosynthesis; the bacteria (like the ones inside tubeworms) turn chemicals into food for other organisms, who then are eaten by other organisms, and thus you have a similar food chain. So, if something happened to block all light from the Sun (but still kept all other physical properties of the Sun intact), that ecosystem would be the one to survive.
*I say for the most part, because some creatures do feed off of food particles that drift down from the surface, which is dependent on the Sun for energy.
7. The fact that hydrothermal vents cycle a lot of nutrients into the oceans. Hydrothermal vents are essential for cycling minerals and nutrients from beneath the Earth’s surface, regulating the oceans.
If you’re still interested in the deep seas, check out the episode of the documentary Blue Planet called “The Deep.” It’s pretty amazing.