The island is a basaltic andesitestratovolcano, and the latest crater, which is about 152 metres (500 ft) across and 61 metres (200 ft) deep was formed from an explosion some time between 1968 and 1984. Its highest point, at 255 metres (837 ft), is Basilisk Peak. Isaacson Point is its southeast point—an area first charted by Discovery Investigations personnel on the Discovery II in 1930. It was named after Ms. S. M. Isaacson, an assistant to the staff of the Discovery Committee.[1]