Geothermal heat often finds it way to the surface of the Earth, and most often beneath the ocean as there isn't a lot of continental land mass in its way out. When this heat reaches the ocean floor its produces a flurry of chemical reactions with the mud there. This mud is the collected debris of dead algae and other oceanic life that has rained down from above. Now the temperature of the water at ocean floor is 3'C, water colder than that becomes less dense and floats upwards. So the presence of geothermal heat is a Great increase in available energy. All this considered together gives a good habitat for life. The collected nutrients laying dormant there are suddenly made available. Bacteria and other microorganisms capable of using heat for synthetic activities (kinosynthetic) provide a food source for any other lifeforms that is down there: crustaceans tube worms, fish, etc etc etc.
Some deep sea vents can be hotter than 300 degrees C.
Volcanic eruptions
It would seem so... mollusks have been found near deep sea vents as well as in high altitude mountain ponds (up to 10,000 feet above sea level).
Some deep sea vents can be hotter than 300 degrees C.
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hot rocks deep in the crust.
surrounding deep-sea hydrothermal vents
Its not so much a theory as a fact. They exist.
Hydrothermal vents allow underground heat sources to warm the ocean bottom which is necessary to support deep see ecology.
near deep-sea hydrothermal vents
near deep-sea hydrothermal vents
such organisms would be bacteria, fungi, protozoa, algae and other microorganisms mostly you would only need to find a rock and have a powerful microscope