Kondalilla Falls

Walk the track to Kondalilla and the forest tells you where you are going before you ever see the water. Up on the tops the country runs open and sunny, eucalypts spaced over a grassy floor, the ground dry underfoot between rains. Then the path tips down toward the sound of falling water. The trees close overhead, the light drops by half, the air cools and dampens, and by the time you reach the gorge you are standing in rainforest: ferns dripping, piccabeen palms crowding the shade, the whole green room humming with damp. You walk out of one forest and into another in a few hundred metres, and the waterfall itself draws the line between them.

Here is why. The Blackall Range is a slab of basalt laid over much older rock, the lava lid of the hinterland, Maleny and Montville and Mapleton riding high on it. A stream crossing the top saws downward, and at Kondalilla it has cut clean through the lava and struck what lies beneath: hard, pale, flow-banded rhyolite, erupted here something like two hundred million years before the basalt ever arrived. You can see it in the rock slab above the swimming hole. That ancient stuff is tougher than anything above it, so it is the rhyolite, not the basalt, that holds the lip. The softer ground below wears back faster, and the water leaps the step between the two. That is a waterfall in one sentence: hard rock over soft, and gravity doing the rest. The same rule stands the whole range up as a flat-topped plateau with a steep, eroding rim. Here you read it as a single bright ribbon pouring off a rock edge older than the range it crosses.

And the fall is not sitting still. Each waterfall on the range is the leading edge of erosion working backwards into the plateau, a stream sawing its gorge headward through the resistant rhyolite, shaving the tableland smaller year by year. The view we drive an hour up to photograph is a freeze-frame of the land caught in the act of wearing itself away.

The two forests follow from the same geometry. The basalt tops are high, so they catch the heaviest rain the coast gets, wringing the moist onshore air out against the range like a flannel; and they weather to the deep red Ferrosol that is the richest soil in the region, the wet, fertile top of the reef-to-range climb, the kind of ground rainforest thrives on (see basalt fertility). But height and rich rock are not the whole of it. The gorge grows the rainforest, adding the one thing the sunlit rim lacks: shelter. Down in the shaded cleft below the fall the forest stays cool, humid and still, the litter too damp to carry a flame, and that fire-free refuge is what lets a rainforest close its canopy and keep it closed (see the fire boundary). Up on the exposed rim, drier and open to sun and fire, the eucalypts hold the ground instead. It is the gradient rule run on a single hillside, and the waterfall marks the seam.

Read the water, too, and it confirms the reading. The stream over the lip runs clear and cool. That is basalt water, filtered slowly through deep clay, and nothing like the blackwater of the sand country down on the coast. Clear cool water off a green range means rich, reliable country, and here it does its last work before the drop, cutting, grain by grain, the very edge that sorts the forest in two.

So Kondalilla packs the whole reef-to-range story into one gorge. Eucalypts on the dry, bright, fire-swept tops, rainforest in the cool wet cleft below, and between them a stream sawing off the hard rock edge and drawing the line as it goes. The country rewards a careful reading, and it punishes a careless step: the rock at the lip and the pools below are slick, and the drop is real.