After the watery interlude at Nelson, we continue our volcano safari east. I am eager to see the “petrified forest”, billed in the Kanawinka leaflet as a Moonah forest drowned by dunes that then hardened. So we head out towards the coast, passing an intriguing string of caves fenced off, a track leading up, but no signs to explain them. Later research told me they were the Tarragal Caves, undercuts in ancient dune limestone and important Aboriginal camping places: excavations in the 1970s revealed shell midden deposits and earth ovens over 11,000 years old.
Cape Bridgewater and the “petrified forest”
We arrive at the wild southern ocean to find a parade of wind turbines there before us, drowning the sound of the sea and intruding on the visual strangeness of the barren landscape: rock and saltbush and then the sea. We walk past what we interpret as hollows left by the dissolution of trees: circles on the ground and tubular shapes in the cliffs. Then we found an information panel that explains that the “forest” is not after all petrified trees, but a collection of hollow limestone tubes, eroded by millions of years of rainfall. This process begins when mineral-saturated water gathers in a shallow pan of sand and seeps downwards, dissolving the limestone and cementing the sand. However it was formed, it is an eerie desolate landscape. A flow of black basalt tumbles down to the sea, beginning grey like a wrinkled elephant hide before it turns typical basalt black.
The approach to Budj Bim (Mt Eccles) is through flattish country towards an undistinguished horizon. The first time I drove out there years ago, drawn by a brown national parks sign, I didn't expect much. A mistake. Apart from koalas, it offers a crater lake, lava tubes and a lava cave.
Our first sight of Budj Bim itself is in cross-section. The whole side of the mountain has been sliced away by a extractinf scoria (igneous rock with bubble-like cavities) for road building.
After we pitch camp we head off to walk around the rim of the crater. Imagine yourself back in the time, 33000 years ago, when Budj Bim was formed. There is boiling lake and frothy lava jets up in a fountain. It cools rapidly to form scoria. There's a wind from the west and it blows the scoria from the crater to build the cone. Then liquid lava splashes onto the sides of the mountain. Some of it sticks and solidifies into basalt: some falls away before it turns solid and leaves gaping holes.
The lake is called Lake Surprise, named by a school child in the 1920s and is contained by three craters.
The next morning we begin the day with a stroll along the remains of a lava tube, the walls towering above us. Overflow from lava or splatter from a turbulent lava flow built up in thin layers to form levee banks. The banks grew inwards to overarch the flow, eventually joining to make a roof. There are signs of a collapsed roof along the lava canal. The deep cave, the natural arch, is one place where the roof hasn't collapsed.
The landscape not far from Budj Bim is scattered with roughly circular mounds of rock: tumuli or lava blisters, created by the buckling of brittle crust by the upward flow of underlying lava.
Beneath lowering clouds, we slither under an electric fence (there were no KEEP OUT signs) and dodging cow pats prowl around an area scattered with tumuli which are “rarely found in the volcanics of the world”: the only other sites are in Africa and Iceland. Sometimes drystone walls connect with the tumuli, a more orderly tumble of rocks.
These caves are the result of action at Mt Napier (see below). The largest tunnels are up to 18 metres wide, 10 metres high, and extend to depths of 20 metres below the surface. The main features of Cave 1 are the ferns and mosses at the entrance and the large circular chamber at the far end with a complete domed lava floor. The western sinkhole is roughly elliptical, and at the western end this leads by various entrances to low-level passages. The western sinkhole is connected to the eastern one by a short tunnel.
The Caves support a sizeable Bent-winged Bat population and offer twenty species of ferns. Mammal bones including those of the Thylacine (Tasmanian Tiger) have been found in the caves.
And no. We entered none of them: the clambering looked too daunting.
Mt Napier and Harman Valley
Looking beyond the Harman Valley, in the distance, is the distinctive shape of Mt Napier. 8 000 years ago a spectacular lava fountain several hundred metres high roared up from a lava lake in Mt Napier's crater from a depth of thirty kilometres. Lava flows surged down several valleys including the Harman Valley, through lava tubes hidden under a solidified crust. Inside the tubes the rock stayed molten and travelled 27 kilometres.
Our last volcanic act in this ten-day volcano crawl is the ascent of Mt Napier, and a fitting end it is. The crater is a dry one and the rim gives a panoramic view out over country we'd been traversing, as far as the Grampians and the wind farms on the coast.