Atlantis Massif spans 10 miles across rising 14,000 feet from seafloor with summit at 700m depth. Sits east of Mid-Atlantic Ridge and Atlantis Transform Fault at 30.13°N 42.13°W. Pulled from under ridge 1.5-2 million years ago by plate movement. Built of dense green peridotite from mantle not black basalt. Central dome corrugated and striated as exposed ultramafic oceanic core complex. Steep detachment fault links to oceanic core complex structure. Mantle material extruded to form dome surface. Hosts Lost City Hydrothermal Field near summit discovered 2000. 1996 expedition identified detachment fault. 2016 IODP 357 expedition drilled cores. Rock age early Pleistocene 2-1.5 Ma.