The Azores consists of an extensive marine and terrestrial system of hundreds of active submarine mounts and volcanoes that extend from the Mid-Atlantic Ridge. The islands of the Azores are the visible representation of the complex ridge of undersea mountains that extend from Iceland to Antarctic. Below the waters of the Azores are undersea valleys and large mountains that are many times larger than the terrestrial continental mountain ranges. Formed by divergent boundary plate tectonics, the region is fractured and susceptible to earthquakes and natural volcanism, resulting in effusive or explosive volcanism. Beneath the Atlantic the formative processes continue to occur producing new land area such as the volcanic eruptions at Capelinhos or Serreta, but also through the venting of gases and pillow lavas, supporting a rich ecosystem.