MILLSTREAM FALLS NATIONAL PARK

The town of Ravenshoe is almost on the western edge of the basalts from the Atherton Volcanic Province, and just to the west, older rhyolite lavas of the Glen Gordon Volcanics (of Carboniferous age) can be seen in cuttings of the Kennedy Highway, beneath pale shallow soils. However, some basalt flows continued further west down an old valley of The Millstream which flows past the town. The park covers a strip of these basalts along the present stream valley below the town.

The basalt flows are believed to have come from the Windy Hill Volcano, whose summit was near the present wind farm east of the town. After the valley was filled by the basalts, the stream had to carve a new course. Usually it cut down along the margin between the flows and the older surrounding rocks, but in places it cut a course in the basalts themselves.

There are two entrances to the national park. The Little Millstream Falls are reached along Tully Falls Road and Wooroora Road to the south of Ravenshoe. A short walking track leads to the base of the falls from the car park. These are cascades and slots cut into hard rhyolite of the Glen Gordon Volcanics, where the present stream has been forced to erode along the boundary of the rhyolite and the basalt flows. Just downstream from the pool at the base of the falls, the edge of a black basalt flow can be seen in the cliff to the south, on top of the rhyolite (photo opposite). Looking down the gorge from the walking track, you can see light grey rhyolite outcrops, pale soils and eucalypt forest on the right-hand side of the valley, and dark basalt outcrops red soils and denser vegetation on the left.

Big Millstream Falls are just off the Kennedy Highway 3 km west of Ravenshoe, where  a walking track leads from a car park to a lookout over the falls. Three basalt fows have been identified, and the uppermost, on which the car park is situated, has been dated at 1.24 million years old. However, a soil profile has developed on top of the next next underlying flow, so this and the lowermost flow may be considerably older The falls plunge in a wide curtain over the horizontal, lowermost lava flow showing how ecology can influence the appearance of streams and falls The lower flows show prominent vertical cooling columns, formed as the flows cooled, contracted and cracked downwards in a regular pattern.

Warwick Willmott

Rocks and Landscapes of the National Parks of North Queensland, Geoscience Australia (Qld Branch)