A geophysical survey to characterize the fundamental structure and evolution of slow-spread oceanic crust with age, and the age range for oceanic crust layers to reach mature velocities. This survey will be the most comprehensive study of oceanic crust at any spreading rate (across a 70 myr age range) and will serve as a foundation for comparison to similar studies of intermediate and fast spreading crust. Additionally, this will serve as a site survey for a proposed IODP drilling transect (853-Pre), which has already been favorably reviewed by the IODP Science Evaluation Panel.