The Lost City field: A new class
of submarine hydrothermal system
Deborah Kelley, Ph.D.
University of Washington
Wednesday, March 6, 2002
3:00 p.m.–Pacific Forum
In December 2000, an important new class of submarine hydrothermal system was serendipitously discovered on the Mid-Atlantic Ridge (30°N). This field, known as Lost City, is located nearly 15 kilometers off-axis on 1.5 million-year-old exhumed mantle rocks. It is more than 300 meters in length and hosts at least 30 active and inactive carbonate chimneys that tower 60 meters above the seafloor. In contrast to black smoker fluids, the Lost City fluids are alkaline and are low in metals and silica. Elevated concentrations of methane and hydrogen are believed to support dense and diverse microbial communities that thrive in the 40-75°C fluids. Circulation is not driven by volcanic heat, but by heat transferred during reactions between seawater and mantle rocks. The Lost City field may represent our closest analogue to early Earth hydrothermal environments and indicates that a much larger portion of the oceanic crust may support life than previously believed.