The island is the eroded remnant of a shield volcano that formed 4.8 +/- 2.0 million years ago, the vent of which is now submerged off the east coast.

[2] Franklin Island is about 290 metres (950 ft) high at its highest point, and about 5 nautical miles (9.3 km; 5.8 mi) long.

The generic has been changed to "Head" by the US-ACAN to avoid duplication with Cape Bernacchi on the coast of Victoria Land.

A reef of rocks, the charted position of which is doubtful, reported to extend about 4 nautical miles (7.4 km; 4.6 mi) southward from Bernacchi Head, Franklin Island, in the Ross Sea.

[5] This article incorporates public domain material from websites or documents of the United States Geological Survey.