And off to the port side, a thick reinforced hose runs beneath the surface to an air gun. Every few seconds, high-pressure air in the hose causes a piston to dart forward in the water. This motion creates a cavity that quickly collapses, each implosion generating a shock wave that penetrates the seafloor below. The hydrophones receive the signals that are reflected back to the ship from the bottom. Inside the lab, the tracings of pen plotters reveal the seafloor and the layers beneath.
Dark bands indicate reflective layers beneath the surface.
We are crossing an abyssal plain just before the African continent begins to rise toward the surface. The layers visible below are neatly parallel. The present equipment produces only a flat cross section. But the initial results are not encouraging. The signals from the single- channel array, strung out on the cable from the starboard side, are black and clear.