National Oceanic and
Atmospheric Administration
United States Department of Commerce


FY 2004

Detection of and response to mid-ocean ridge magmatic events: Implications for the subsurface biosphere

Cowen, J.P., E.T. Baker, and R.W. Embley

In The Subseafloor Biosphere at Mid-Ocean Ridges, W.S.D. Wilcock, E.F. DeLong, D.S. Kelley, J.A. Baross, and S.C. Cary (eds.), Geophys. Monogr. Ser., Vol. 144, AGU, 227–243 (2004)

Magmatic events are unpredictable dynamic processes that are integral to the evolution of mid-ocean ridges. Dikes and lava flows develop rapidly and instantly alter the local hydrothermal flow regime, initiating dramatic changes in hydrothermal discharge at the seafloor, and triggering geochemical and microbiological changes within the shallow crust, at the seafloor and within the overlying water column. Despite considerable logistical difficulties, real-time remote detection capabilities (SOSUS) along limited regions of the MOR system have allowed investigators to rapidly respond to significant seismic events. There have been more than 20 documented examples of seafloor volcanic/tectonic events, at both isolated volcanoes and mid-ocean ridges, but only a few of these have led to significant response efforts. The most rapid and thorough response efforts have been to the 1991 9°N EPR event and several events (1986, 1993, 1996, 1998, 2001) on the Juan de Fuca and Gorda Ridges. Together these "SOSUS directed" responses plus the few serendipitous encounters have led to important discoveries (e.g., event plumes; "snow-blower" vents) and provided basic new constraints on presently immature models of submarine magmatic-hydrothermal systems (e.g., intrusive/extrusive diking; event plume formation; subsurface hydrothermal communities). The event response community has gained valuable experience in learning how to exploit these opportunities for scientific observation and is currently poised to continue such studies with increased speed and efficiency. However, our understanding of these geophysical, chemical and biological processes is only in their infancy.

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