New oceanic crust is made at a rate of about 1m every decade all along the north-south trending East Pacific Rise (EPR) in the eastern Pacific Ocean. This ocean spreading center has erupted twice in the last two decades near 9° 48’N producing extensive lava flows on the seafloor. A nearly continuous magma chamber has been imaged seismically along much of the EPR between the Siqueros and Clipperton fracture zones.

1. 1)The eruptions periodically tap the underlying magma chamber which is refilled by magma percolating from the upper mantle through the lower oceanic crust. It is thought that magma erupts as a “dike” tapping some portion of the underlying magma. In 2006, Milene Cormier, Roger Buck, Scott Nooner and I deployed 19 bottom pressure recorders on the seafloor between about 9° and 10° N in the East Pacific Rise. The goal of this simple experiment is to observe changes in seafloor elevation (as inferred from the pressure observations) associated with magma movement and eruptive activity. The pressure gauges will be recovered in late December 2009 after monitoring changes in seafloor pressure over more than three years.  Buck and Nooner are working on modeling the elevation changes that one might expect to see from a diking event.                                                                                                                
   

2. 2)Scott Nooner leads a second project that uses observations on ten benchmarks deployed on the seafloor     to monitor very accurately the slow reinflation of the magma chamber following the eruption at 9°48’N in 2005-2006.  A submersible (Alvin) or an ROV (Jason) is used to repeatedly deploy two precise pressure gauges sequentially onto these benchmarks. The measurements constrain the relative elevation of the benchmarks to an accuracy of 1cm. The measurements will be repeated roughly every year allowing an accurate determination of the gradual reinflation of the magma chamber or possible deflation associated with magma movement.
   

3) We have begun scheming for a new program of marine geodesy in the Atlantic on a new type of problem.