Plate tectonic boundaries of the southwest Pacific. Australia is far from the edges of the Indian-Australia plate yet volcanoes have been erupting along the east part of the continent for the last 33 million years. Australia's volcanoes are not related to the subduction zones that produce volcanoes in New Zealand, the Kermadec Islands, Tonga, Samoa, and Indonesia. The "teeth" (black triangles) are on the over-riding plate at each subduction zone. Spreading centers are marked by divergent arrows. Transform faults marked by opposed arrows. Modified from Johnson and others (1989)
The volcanoes of Australia define several chains with progressively younger volcanoes to the south. Ages are shown in millions of years. These age progressions suggest that a hot spot feeds magma to the volcanoes. Unlike the Hawaiian, Society Islands and Yellowstone hot spots, which produce a single chain of volcanoes, the hot spot beneath eastern Australia is broad and may take advantage of weak places in the plate to feed magma to the surface. Based on the map, which direction is Australia moving and about how fast?
Volcanic centers of eastern Australia. The volcanoes extend 4400 km from Maer Islands (500 km north of Queensland) in the north to Tasmania in the south. Three types of volcanic centers are shown. Central volcanoes are capped by silica-rich trachyte and rhyolite lavas. Lava fields are formed by effusive eruptions with little explosive activity. Leucite suite refers to volcanoes that erupted lava and tephra containing the mineral leucite. These rocks are relatively low in silica and rich in potassium compared to most basalts.
Volcanic centers in Queensland. Compiled from Sutherland (1995) and Johnson and others (1989).
Volcanic centers of New South Wales and Victoria.
The most recent eruptions in Australia were at Mounts Schank and Gambier of the Newer Volcanic Province of Victoria and South Australia. The Australian plate is moving north at about 75 km/million years or 7.5 cm/year.
Additional information is available on the Volcanoes of Victoria homepage.
Click here for information on the Caldera of the Tweed Volcano.
Sources of Information:
Johnson, R.W., Knutson, J., and Taylor, S.R., editors, 1989, Intraplate volcanism in Eastern Australia and New Zealand, Cambridge, England: Cambridge University Press, 408 p.
Lewis, G.B., Mattox, S.R., Duggan, M., McCue, K., 1998, Australian volcanoes educational slide set: Australian Geological Survey Organization.
O'Reilly, S.Y., and Zhang, Ming, 1995, Geochemical characteristics of lava-field basalts from eastern Australia and inferred sources: connections with the subcontinental lithospheric mantle?: Contributions to Mineralogy and Petrology, v. 121, p. 148-170.
Sutherland, L., 1995, The Volcanic Earth: Sydney, University of New South Wales Press, 248 p.
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