The bathymetric surveys conducted in 1883 found, where before we had the island, a vast and low bottom 16, which rose up, up to -2.7 and -3.3 m, two pinnacles of hard rock (basalt), probably the remains of the fire power of the volcano, which were destroyed with explosives because of the danger it posed to navigation. Hydrographic Institute of the Navy, in 1914, reported a depth of 50 m, with two culminations deep - 34 (the West) and -8 m (the East). Measurements carried out by the National Research Council in 1972 indicated a shallow sub-level, between -20 and -30 m, with a central spire isolated basalt that rose up to a depth of -8.8 m. Hydrographic Institute of the Navy, in December 2002 and May 2003, revealed the highest point of the old volcano surface to -6.9 m. It appeared that the Ferdinandea is part of a large and composite building, elongated NW-SE (2,500 × 1,500 m), consisting of a common base on which stand two coalescing cones. The cone that erupted in 1831 and has built the ephemeral Island Ferdinandea 160 m high and has a base diameter of 500 m and is accompanied to the north-west by a cone larger (base 1500 m, height 200 m, height - 16). This second building is easily recognizable, the remains of a more ancient crater edge, 1.3 km wide, which is followed by NE (- 100 m) to SE (-80m) to SO (-120 m), from this crater and probably leaked out to O-SO a well-defined and stocky casting wides (1.5 km) long (0.8 km), which drops to about -110 m, invading the marine floor, to the depth of more than 200 m.
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