The Lost City Hydrothermal Field (LCHF) was serendipitously discovered in 2000 near the summit of the Atlantis Massif. The geology, chemistry, and biology of this venting system are different from anything previously found. The LCHF is located about 15 km (9 mi) west of the Mid-Atlantic Ridge and is characterized by tall (up to 60 m or 200 ft) limestone chimneys emitting 40–91°C (104–196°F) alkaline fluids that contain elevated concentrations of dissolved hydrogen and methane. The chemistry of the field is controlled by reactions between the underlying mantle rocks and seawater circulating within the mountain in a process called serpentinization. This hydration reaction produces heat, which helps drive hydrothermal circulation at this site. The LCHF is a new class of hydrothermal system that may yield insights into early life on Earth, and likely it is not unique within the ocean basins.