page_title: Axial Seamount
section_title: Tectonic setting
hierarchical_section_title: Axial Seamount / Geology / Tectonic setting
context_page_description: Axial Seamount is a seamount and submarine volcano located on the Juan de Fuca Ridge, approximately 480 km west of Cannon Beach, Oregon. Standing 1,100 m high, Axial Seamount is the youngest volcano and current eruptive center of the Cobb–Eickelberg Seamount chain. Located at the center of both a geological hotspot and a mid-ocean ridge, the seamount is geologically complex, and its origins are still poorly understood. Axial Seamount is set on a long, low-lying plateau, with two large rift zones trending 50 km to the northeast and southwest of its center. The volcano features an unusual rectangular caldera, and its flanks are pockmarked by fissures, vents, sheet flows, and pit craters up to 100 m deep; its geology is further complicated by its intersection with several smaller seamounts surrounding it.
  Axial Seamount was first detected in the 1970s by satellite altimetry, and mapped and explored by Pisces IV, DSV Alvin, and others through the 1980s. A large package of sensors was dropped on the seamount through 1992, and the New Millennium Observatory was established on its flanks in 1996.
context_section_description: Axial Seamount is the youngest volcano and current eruptive center of the Cobb–Eickelberg Seamount chain, a chain of seamounts that terminates south of Alaska. Axial lies where the chain intersects with the Juan de Fuca Ridge, approximately 480 km (298 mi) west of Oregon. It is a product of the Cobb hotspot, but now sits on an ocean spreading center between the Juan de Fuca Plate and the North American Plate, offset by the Blanco Fracture Zone to the south and a ridge-built triple junction to the north.
  This position is not yet entirely understood. It is believed that the chain, formed over millions of years by the now-inactive Cobb hotspot, is older than the mid-ocean ridge it bisects. Between 200,000 and 700,000 years ago, the hotspot was encroached by the tectonic spreading center, displacing it by as much as 20 km (12 mi) and building up the 500 km (311 mi) long Juan de Fuca Ridge. At least 7 spreading centers have been recognized, and plate measurements near Axial show that the ridge is separating at a rate of 6 cm (2 in) per year, producing a complex system of oceanic basins and ridges. However some scientists have questioned this theory, pointing out that the high density of the chain's overlapping seamounts is incompatible with such an origin, as a hotspot would form a well organized, widely spaced chain. Although the exact nature of Axial Seamount remains unknown, its complex origins makes it one of the most geologically interesting features in the North Pacific.
caption: Position of Axial Seamount relative to the Juan de Fuca Ridge.