Source: NOVA: "Volcanoes of the Deep" Less than a century ago,
people expected the ocean floor to be as featureless as the
surface of the water above. However, underwater explorations
revealed quite the opposite: towering mid-oceanic ridges and
deep ocean trenches. This video segment adapted from NOVA
reveals the unexpectedly rich ecosystems researchers found when
they looked more closely at the seafloor near mid-ocean ridges.
Seafloor spreading generates new ocean crust, but it may also
have created conditions necessary for the beginning of life on
Earth. At mid-ocean ridges, molten lava pushes through breaks in
the crust during amazing undersea volcanic eruptions. This
molten rock quickly cools, and as it does, it contracts, forming
long cracks and fissures. Ocean water seeps into these cracks to
a depth of several kilometers, where it is heated by magma in
Earth's mantle to as much as 350 degrees Celsius (660 degrees
Fahrenheit). This superheated water then rises and eventually
emerges from hydrothermal ve