Figure 20.21High-technology methods for exploring the deep seafloor. The manned deep submersible Alvin and a remotely operated vehicle (ROV) are directed from a surface ship. SeaBeam, a hull-mounted multibeam echo sounder, continuously maps seafloor topography in a wide swath as a ship steams across the ocean surface. The drilling ship JOIDES Resolution (see also Figure 2.13), part of the Ocean Drilling Program, uses bottom transponders to maneuver a drill pipe into a reentry hole on the seafloor. Permanent unmanned seafloor observatories can monitor processes in the subsurface and the overlying water column for extended periods.