R/V Marcus G. Langseth leg MGL0910 conducted a multi-scale seismic tomography experiment on the Endeavour segment of the Juan de Fuca Ridge (ETOMO). During the 30-day leg, 64 four-component, ocean bottom seismometers (OBSs) were deployed throughout a 90x50 km*2 area to record seismic energy from the 36-element, 6600 cu. in. airgun array of the R/V Marcus G. Langseth. At the segment scale (~90 km along axis), the ETOMO experiment constrains the nature of sub-ridge mantle flow and the pattern of melt transport from the topmost mantle to the crust beneath the entire Endeavour segment. These ‘undershoot’ data provide a direct test of competing models for the origin of ridge crest segmentation and, in particular, provide critical data for determining if skew of mantle upwelling and melt transport is common phenomena beneath spreading centers. Also at this scale, the ETOMO data provides direct measurements of crustal thickness which will be used to understand the history of segment-scale magma supply. At an intermediate scale of approximately 60 km along axis and 20 km across axis, the ETOMO experiment constrains the size, shape, and distribution of crustal magma bodies that fuel the Endeavour hydrothermal system. Data from the ‘crustal grid’ of seismic surveying will provide one of the largest 3-D images of a crustal magmatic system for any volcano on Earth. At a smaller scale that is focused on the vent fields themselves, data from ETOMO will constrain the physical properties of the reaction zone between the magmatic and hydrothermal systems. Taken as a whole, data from the ETOMO experiment will be able to track the seismic signature of heat and mass transport from the mantle to the seafloor at the Endeavour segment, thereby achieving one of the primary goals of the RIDGE 2000 program for the Endeavour Integrated Study Site.
The Endeavour seismic tomography experiment (ETOMO) experiment will test competing models for what controls the segmentation and intensity of ridge crest processes. Existing models are at odds on the scale of mantle and crustal magmatic segmentation, the distribution of hydrothermal venting with respect to a volcanic segment and the properties of the thermal boundary layer that transports energy between the magmatic and hydrothermal systems. The recent discovery of an axial magma chamber (AMC) reflector beneath the Endeavour segment of the Juan de Fuca ridge, as well as systematic along axis changes in seafloor depth, ridge crest mor...