Primordial Lismore
All life as we now know it bears much to the geological events which took place some 23 million years ago during the Miocene Epoch. The local landscape was shaped dramatically by lava flows from the Tweed Shield Volcano. During the height of its activity, the lava flow extended from the Tweed River basin area to as far afield as the mid-Richmond. To the west the flow extended to Kyogle and some 30 kilometres into the sea to the east.
The first of the lava flows consisted primarily of basalt. Over millions of years the basalt eroded away leaving a hard plug of volcanic rock in the centre of what was the shield volcano. This plug is today known as Wollumbin or Mount Warning. The surrounding shield wall remains today to the north west as the MacPherson Range, to the west as the Tweed Range, and south west as the Nightcap Range. The Tweed River Shield Volcano is the largest of its kind in Australia. Volcanic activity became extinct some 3 million years ago.
The original caldera of the Tweed Shield Volcano had a radius of some 16 kilometres with the centre being Wollumbin. Subsequent smaller lava flows occurred at a number of places, forcing its way up through many vents and forming rhyolite rock which was more resistant to weathering than the previous basalt. Over millions of years, the underlying basalt rock eroded away, causing some sections of the prominences to collapse. The results of this collapse are the steep cliffs noticeable today in the Nimbin district.
As volcanic activity waned, atmospheric conditions became conducive to significant rainfall generated by nearby seawater and land-generated heat. The high prominence of Mount Warning (now just over half its original height of 1900 metres) attracted moisture-laden ocean air that condensed on rising over the mountain and associated ranges. The resultant rainfall on the southern shed of the Nightcap Range formed water systems which fed into the Wilsons River, namely the Goolmangar, Coopers and Terania Creeks. The Back Creek and Hanging Rock stream system developed with their headwaters in the Kyogle area and merged to form Leycester Creek, which in turn joins with the Wilsons River in Lismore.
The river systems carried mineral silt down from the ranges to the lowlands forming rich volcanic soils. A combination of high rainfall, warm climate and the rich basaltic soils led to the creation of unique subtropical rainforests found nowhere else in Australia. The rainforests provided sanctuary for many species of bird life including the lyrebird, brush turkey, green cat bird, double-eyed fig, bush cuckoo, marbled frogmouth, brown warbler and many more.