Submarine volcanism

Part A: Eruptive processes

Part B: Hawaiian coral reefs

Project Manager: Alicé Davis
Lead Scientist: David Clague

Lead Engineer: John Graybeal

The Submarine Volcanism project has the broad goal to gain a better understanding of the processes that form and modify oceanic volcanoes. Over the past several years, we have begun to focus on the style of submarine basaltic eruptions and the process of lava fragmentation in a variety of geologic settings. Although work on lava flow emplacement, particularly of fluid lavas on gentle slopes continues, more of our effort has been focused on the character and dynamics of submarine explosive eruptions on mid-ocean ridges, on Loihi Seamount, seamounts offshore central California, and on the deep sea floor around the Hawaiian Islands. These studies have been made possible by our newly developed ability to sample these fine-grained and dispersed eruptive products using ROVs and manned submersibles, as well as new insight that allows us to map these deposits on the seafloor to determine their distribution. We have now collected, identified, and analyzed the fine-grained fragmental products of strombolian eruptions, hawaiian-style lava fountains, and phreatomagmatic eruptions, which refute the traditional view that deep sea eruptions (>1000 m) are entirely effusive. We have also begun to tie the eruptive style not only to characteristics of the erupting magmas, such as volatile contents, viscosity, and eruption temperature, but also to structures on the volcanoes, such as the presence of calderas or other collapse features. We propose to continue to develop this research direction by focused mapping and sampling of some specific volcanic features located within distance and depth range of Tiburon and to seek outside support for a new program on Loihi Seamount, where some exciting results have been obtained. The MBARI work we propose over the next several years will continue to study mildly to moderately explosive eruptions on mid-ocean ridges (Gorda Ridge, East Pacific Rise), near-ridge seamounts (President Jackson, Vance, and Taney Seamounts), and on seamounts offshore central and southern California.

We also propose to expand our work into the realm of silicic submarine explosive eruptions by performing a few manipulative experiments using the ROVs. Many of the volcaniclastic, silicic deposits on land have been erupted in the submarine environment. Shape and size of volcaniclastic material is key to interpreting eruptive processes. To determine the rates of saturation and sinking of pumice fragments yields information on the grain size distribution of fragmental deposits from silicic submarine eruptions. A few preliminary experiments, during the seamount dives in 2003, would allow us to devise a longer term program to experimentally determine many of the parameters that define submarine, silicic, volcaniclastic deposits and help determine the characteristics of such deposits when they erupt in a submarine environment.

Continued utilization and refinement of the GIS-navigation, 3-D data visualization and MBARI's sample data base is critical to our mapping and sample management efforts.