Knowing the Wonder – Part 3

The trail up the Carnarvon Gorge  winding for 10 kilometres from the Rangers Office to Cathedral Cave crosses the spring fed Carnarvon Creek many times and one of the fun challengers for walkers is making it across on the steppingstones without slipping in.

Crossing Carnarvon Creek

Crossing Carnarvon Creek

Though there is nearly always abundant surface flow, what the walkers don’t see is that much of the flow is hidden in the river gravels. Indeed where the creek emerges from the ranges into the open plains the riverbed is almost always dry on the surface though there may be abundant groundwater. As well as this, the Precipice Sandstone is a major intake bed for the great Artesian Basin, meaning that much of the rainfall in the ranges will end up feeding the artesian bores much further west.

In the month of February 1973, over thirty inches (770mm) of rain was recorded in Carnarvon Gorge including six inches (150mm) in one night. The creek rose some twenty feet and thundered through the Gorge carrying an enormous load of silt, gravel and vegetation. Huge eucalypt trees were ripped out and sent hurtling downstream as they were stripped of roots and branches. The island at Aljon was completely washed out and the stream channel changed in many other places. A number of new major landslides occurred along the gorge walls. Parts of the main walking track had to be relocated to bypass the debris and cross the creek at new locations. A similar event occurred in the summer of 2011 destroying long sections of track, scouring and widening the channel, and leaving flood debris high up above the creek banks.

The Gorge is not a monument to Noah’s Flood as some so called Biblical theologists would have us believe.IMG_0086 If you do the sums, one or two major foods taking away just one centimetre of rock in a hundred years equates to hundred metres in a million years. It can be difficult to get your head around the immensity of Geological time, but the evidence of the erosion is there in the gravel and sand load carried by the stream. Chunks of basalt and other igneous rocks transported long ago from high up on the plateaus and ranges are among the steppingstones that allow the visitor to cross the creek safely.

About rpsimson1936

Retired geography and outdoor education teacher who loves orienteering and writes novels.
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