sentences:  The acoustic transponder capability eventually evolved into instruments for acoustic geodetic measurements by combining the technologies of seafloor acoustic beacons with shipboard GPS positioning.This geodetic system has been successfully deployed for directly measuring the direction of movement and speed of the oceanic Juan de Fuca lithospheric plate and for documenting movement on submarine landslides.During the mid 1970s, several deep-tow cruises to the mouth of the Gulf of California at 21o N resulted in production of a geologic map of the East Pacific Rise (EPR) spreading ridge axis.