Carlo Sandblow

Walk up through the forest behind Rainbow Beach and you climb out of the trees into something that looks less like a dune than a desert someone has parked on top of the coast: the Carlo Sandblow, a vast open sheet of bare, blinding sand spilling over the cliff-tops, hundreds of metres across, the sea on one side and, on the other, the forest it is quietly eating. On a windy day the surface itself streams, grain over grain, and you finally understand what you are looking at. This is not a beach that lost its way and wandered uphill. It is a dune on the move.

A sandblow is a transgressive dune, a parabolic blowout, kept bare and mobile by the onshore wind, which strips it of anything that tries to root and drives it slowly inland across the top of the coloured cliffs, on the northern edge of the great Cooloola sand mass. A dune that walks does two different things at its two ends. At the front, the advancing edge buries whatever stands in its path, so the leading slope is a slow-motion drowning: the crowns and bleached poles of dead trees jut from the sand where the blow has climbed over a living forest and smothered it. Behind, on the trailing edge, the sand marches on and uncovers the ground it crossed a generation or two ago, sometimes letting the dark, organic-stained floor of a long-buried forest back into the light.

That second act makes the sandblow something rare on this coast: a beginning you can stand in. Almost everywhere else, the sand country tells its story in the past tense, in soils that have had hundreds of thousands of years of rain through them. Leaching on that scale needs one thing to get started: a dune that has finally stopped walking, put down roots, and held still long enough for the rain to begin its slow theft. The sandblow is that same sand with the clock set back to zero. The grains under your feet are raw, pale and barely weathered, sunlit and endlessly reshuffled, and while the wind keeps them moving the leaching cannot even begin. Time zero for the podzol story.

Then look at the colour, because Rainbow Beach earns its name honestly. The old sand cliffs below the blow run in bands of red and orange and yellow, dune sands stained over long ages by iron and aluminium oxides. Read that against the bright bare sand of the blow itself: the two are the same substance at opposite ends of time, and the same weathering chemistry underlies both. Inland, that chemistry strips the iron down and out of the surface, leaving bleached quartz over dark hardpan; here in the coloured cliffs it has left the iron behind as pigment, colour rather than bleach. (The reading is a regional geological one, drawn from the rock, not a laboratory assay of these particular cliffs, but it is the same iron and the same rain, showing up two different ways.)

One landform, then, with two ages in it. Raw, sunlit, un-started sand at the bow. At the stern, ground that went under a generation or two ago, where the blow surrenders old forest floors back to the light, the kind of organic-stained layer that, elsewhere in this country, ends up sealing the floor of a perched lake. Carlo is Cooloola’s sand at the very start, caught in the act of walking.