Lying approximately at the junction between the South Indian and Pacific Oceans, Macquarie Island is situated at 54.30'S 158.57'E and 1,466km southeast of Hobart. The island boasts a superb flora and wildlife, including 20 species of breeding seabirds. Ecologically and climatologically Macquarie fits well within the north-south gradient of New Zealand-owned island groups. However, its closeness to the Antarctic Convergence exerts a strong influence on the composition of the flora and fauna. The main island is elongated and measures 33km by 5km. In addition to a number of offshore stacks and reefs, a small group of islands, the Judge and Cleak Islets, lies 11km north of Macquarie and the Bishop and Clerk Islets 37km to the south. Earthquakes are common in the area, with a mean one per annum measuring above 6.2 on the Richter scale.

Macquarie Island, which has never been part of a continent, is geologically unusual. It emerged above sea level between 90,000 and 300,000 years ago and is a rare example of uplifted oceanic crust formed about 27 million years ago at depths of between 2,000 and 4,000 meters. An outstanding example of a major stage of the earth's evolutionary history. It is perhaps the best preserved fragment of deep oceanic crust known above sea level. It is therefore of great interest to scientists studying the phenomena of sea-floor spreading and continental drift. Volcanic blocks (mainly pillow lavas), basaltic dykes, and various sediments compose about 80 percent of the land.