Oceanic volcanic islands develop above mantle hotspots or along mid oceanic ridges where the sea floor is spreading. The Hawaiian Ridge is an example of the former; its chain of islands, atolls and seamounts formed as the Pacific Plate moved northwestward above a mantle plume, a process that continues today. Iceland, on the other hand, has formed (and continues to form) above the mid Atlantic ridge, between the North American and Eurasian Plates, where oceanic crust is forming.
Axial Seamount, 300 miles off the coast of northwest Oregon, is the product of both volcanic processes. Sitting atop the Juan de Fuca Ridge, a spreading center between the Pacific and Juan de Fuca Oceanic Plates (the latter is a remnant of the Farallon Plate), this Seamount is also fed by magma from the Cobb Hotspot; indeed, the Axial Seamount is the youngest (and currently active) formation in a chain that leads northwestward to the Aleutian Trench. Like the Hawaiian Archipelago, the Cobb-Eickelberg Seamount Chain formed as the Pacific Plate moved northwestward above the hotspot.
Axial Seamount, which appears to have erupted over the past week, rises 3000 feet above the adjacent sections of the Juan de Fuca Ridge; its summit is approximately 1400 meters below the surface of the sea. Whether it will eventually breach the surface to become a volcanic island will be determined by the ongoing relationship between the Cobb Hotspot and the Juan de Fuca Ridge.
