Deep–sea eruptions

Overview The most abundant and widespread volcanic behavior on Earth is the effusive eruption of basaltic lava on the ocean floors – most of it from mid-ocean ridge eruptions. The inaccessibility of the deep (> 500 m below sea level) sea floor limits direct observations of submarine volcanic phenomena. Observations of volcanic products are therefore the primary means by which the dynamics of mid-ocean ridge eruptions are constrained and evaluated. Submarine lava flow morphology can be used to constrain local flow rate if lava viscosity is known. Recent deep (> 500 m) explosive eruptions of seamounts have been directly observed. Introduction The majority of Earth’s surface is covered with oceans, and the oceanic floors are underlain by basaltic lavas erupted at mid-ocean ridges. The most common volcanic eruption on Earth is a submarine, mid-ocean ridge eruption, and understanding the processes that occur during these volcanic events provides a strong foundation for understanding other submarine eruptions. Although Iceland, located at the intersection of a mid-ocean ridge and a mantle plume, provides an opportunity to examine mid-ocean ridge eruptions on land, it is important to remember that Iceland is not a typical mid-ocean ridge volcanic system. Throughout this chapter, then, the phrase “mid-ocean ridge” will refer to the submarine variety unless otherwise stated.