Pic du Mascarin

Île de la Possession, located immediately W of Ile de l'Est in the Crozet archipelago, consists of a stratovolcano intruded by ring and cone dikes and modified by block faulting, marine erosion, and uplift. The structural center of the volcano is located on the W side of the 14 x 19 km island, which has an irregular shoreline. The stratovolcano was formed during at least five stages dating back to the Miocene. The eruption of plateau basalts from a rift system during stage IV was followed by a glacial period and then by the eruption of scoria cones and lava flows. The young scoria cones are of probable Holocene age and are distributed over much of the island, concentrated at the structural center on the W side and along a series of N-S and NE-trending fractures. The Mont Branca cone on the W flank has been estimated by Bellair (1964) to be not more than a few centuries old.