Sunlight is essential to all life on Earth – without light there is no photosynthesis which leads to no oxygen and without oxygen no lifeform can survive. A fact we all learn from an early age in school. And although it is mostly correct, as in everything else, each rule has its own exception.
Many of you probably imagine the ocean floor as a dark and desolate place, devout of life. This, however, is far from the truth. There are vast mountain ridges lining the bottom of the seas, boiling with volcanic activity. As the tectonic plates crash or spread apart, they create deep chasms into the Earth’s crust, where hot magma rises to the surface. The ocean’s water seeps into those cracks, sometimes for hundreds and thousands of meters and becomes superheated. Pressure starts to build and soon, just like a geyser, the water shoots back upwards. Due to the extreme temperature, on its way it dissolves all kinds of metals and minerals which it encounters and brings them to the surface. The water which erupts from the Earth’s crust can reach a temperature up to 400 degrees C, however the high pressure on the ocean floor does not allow it to boil. As it cools down, the dissolved minerals within it solidify and build up layers, forming enormous chimney-like structures. These are called hydrothermal vents, and some have been known to reach up to eighteen stories high.
Not only is the water from the deep-sea vents extremely hot, but it is also very toxic. The heavy metals which it contains mean that it is poisonous to most life forms and the acidity levels can be as high as those of vinegar. Incredibly, instead of inhospitable wastelands, around these inhospitable environments there are whole ecosystems, thriving in the complete absence of light. Instead of photosynthesis they rely on hydrogen sulfide and a process called chemosynthesis. Small, specialized bacteria absorb carbon dioxide from the vents and oxygen from the ocean water to oxidize the sulfur and create organic molecules. They are able to survive at up to 113 degrees C, the highest ever recorded for a living organism and form the basis on which all life in the system depends. Since their discovery in the late 70s, more than 300 different species have been identified, most of which are unique to their particular vent.
The organisms around deep sea vents are one of the most ancient creatures, that we know of. There are giant tubeworms, over 30 centimeters in length, shrimps, crabs, slugs, anemones and even fish. Amazingly, animals in isolated pools of life, thousands of kilometers apart, have been found to be extremely closely related, prompting some scientist to believe, that the first life on Earth may have originated in similar conditions at the bottom of the seas.