Geologically, Strombolicchio is a volcanic plug or spine of extremely hard compacted basalt resistant to erosion, and is the remnant of the original volcano from which the island of Stromboli was built up.

It is the only remnant above sea level of an otherwise submarine platform that extends between it and the main island.

Strombolicchio hosts some very rare species of flora and fauna and has been declared a natural reserve, with severe restrictions on access.

Bassia saxicola, for example, an endangered flower at risk of extinction, is otherwise present in only a few hundred specimens on the island of Capri.

Podarcis raffonei, a rare lizard classified as at critical risk of extinction, is found at only three other locations, all of which are in the Aeolian Islands: a small islet off the coast of the nearby island of Salina, another islet off the coast of Filicudi, and in some areas of Vulcano.