The subsurface endospore dispersal theory. Thermophilic bacteria originating from deep subsurface petroleum reservoirs undergo an upward warm-to-cold translocation through the ocean crust via natural cracks in the impermeable layers of the rock. Thermospores, able to survive this transition are then expelled into the ocean along with petroleum fluids where they are further dispersed by the ocean current over long periods, before settling onto the ocean floor.