Volcanic activity at McDonald Island
McDonald Island began erupting in 1992, after lying dormant for 75,000 years. It has erupted several times since with satellite pictures in 2001 showing that the island had doubled in size. The initial evidence came in the form of abundant pumice washing up on beaches north and south of The Spit at the eastern extremity of Heard Island, directly to the east of McDonald Island.
The then Minister for the Environment and Heritage, Senator Ian Campbell, announced at the opening of the Heard Island Parliament House exhibition that recent satellite imagery shows that eruptions on McDonald Island are continuing.
Heard Island and the McDonald Islands sit atop a shallow submarine plateau – the Kerguelen Plateau – underlain by thinned continental crust. Each of the islands draws their lava from a common source, though there are distinct differences in the quality of the lavas.
While many volcanoes erupt explosively with freely-flowing lava pouring down the side of the volcano, McDonald Island exudes lava that is highly viscous and flows very slowly. Photographs from satellites clearly show where oozing lava has solidified close to the volcano’s vent.
Pumice has accumulated in places where previously there was no beach. The edges of the land mass may have risen slightly, providing more habitat for animal colonisation. Many features, such as small islets and coves are now incorporated into a bigger and more coherent land mass.
Like Heard Island, the McDonald Islands support a burgeoning population of sea birds. When last surveyed in 1980 macaroni penguins were highly abundant. In all probability the new beaches will consist of gravel-like pieces of pumice, and be quite suitable for penguin breeding.
It is unlikely the act of eruption would have had a serious effect on bird life. At this time of year most penguins are still at sea putting on fat necessary for the breeding season. They will return between late August and late September to lay their eggs. Seals will come ashore from October for the birthing and mating seasons. Vegetation high on the slopes (mainly subantarctic tussock grass, Kerguelen cabbage, and cushion plant, will have been affected, but experience from study of Heard Island suggests that natural re-colonisation will quickly occur.