By Samuel Georgian, Marine Biogeographer at Marine Conservation Institute

 
Gumdrop and Pioneer Seamounts
Gumdrop and Pioneer are neighboring seamounts located approximately 45 miles off the coast of California, close to San Francisco. The summit of Pioneer Seamount sits approximately half a mile (2,690 feet) below the surface, while Gumdrop Seamount is even deeper – 3,960 feet down. The seamounts are largely made up of various forms of basalt – a common volcanic rock type that forms when iron-rich lava cools quickly. Unlike many seamounts, which often form at the tumultuous intersection of two or more tectonic plates, they are both examples of intraplate volcanoes. Along with neighboring seamounts including Davidson, Guide, and Rodriguez, these types of volcanoes form within a single tectonic plate due to plumes of extremely hot mantle forcing its way through weaknesses in the Earth’s crust – in this case, likely due to the occurrence of an ancient spreading center.…