Australia: The Land Where Time Began

A biography of the Australian continent 

The Grampians rise above the surrounding pains of the Wimmera district of western Victoria. There are a range of environments within the ranges, gullies festooned with ferns, long escarpments above flat valleys and barren gorges, and in places fast-flowing streams, sometimes falling as waterfalls. There is a wide range of vegetation types, relicts of past climatic regimes.

They are considered to be the southwestern extremity of the Great Dividing Range, though they are younger, are of different rock type and are separated from the ranges of eastern Victoria.

They trend approximately north-south, and are about 100 km long by 55 km wide, being comprised of 3 main sets of ranges and a number of smaller ranges. The longest range is the central ridge that is made up of 2 major sections, the Mount Difficult Range and the Serra Range. This central ridge connects the most northerly peak, Mt Zero, to Mt Abrupt and Mt Sturgeon, the most southerly peaks. The Mt William Range, higher and shorter than the central range, lies to the east. At 1166 m, Mt William in the the Mt William Range is the highest mountain in the Grampians. The Victoria Range to the west of the main range is lower, and is best known for its flora and a number of Aboriginal rock painting sites.

The sedimentary rocks that comprise the Grampians were deposited over a period of about 50 million years, beginning about 395 Ma. The sediments were deposited to a depth of about 6,000 m when compacted, in what is believed to have been an inland sea, possibly of fresh water. The resulting rocks are in the form of alternating beds of highly resistant quartzose sandstone and layers of less resistant siltstone and mudstone. Subsequent folding of these rocks produced the ranges with sloping sandstone and shale strata, as well as grey granite intrusions. Later erosion has removed much of the shale leaving the more resistant sandstone in asymmetrical ridges, often with steep east-facing escarpments, and with sloping western sides. This formation has been called a cuesta. Fyans Valley, between the Serra Range and the Mt William Range, can be viewed from Boroka Lookout.

The narrow, 6.5 km long Wonderland Range, one of the most scenic features of theses ranges, lies between the Serra Range and Mt William range. Grand Canyon Gorge, on the lower slopes of the range, is one of the most popular attractions of this range. This small range has been heavily eroded along the horizontal bedding and along vertical joint lines, giving it the appearance of being constructed of steel-grey building blocks. A stream trickles through the gorge.

Near the top of the range is another gorge, Silent Street. The name is based on its fancied resemblance to a narrow Spanish lane, in which the walls were thought to look like grey buildings and some shrubs at one end of the gorge have the appearance of trees planted in the pavement and the patches of vegetation on the walls adding to the effect by their resemblance to window boxes. Weathering has eroded the rocks of Wonderland Range into many unusual shapes, many of which have been given names, such as Lady's Hat, Mushroom Rock. A large slab that fell from the Wonderland escarpment has been called the Fallen Giant, and a projecting slab, 10 m long and 0.5 m wide has been called Nerve Test. A peak that was used by the early Europeans in the area to tell the time has been called the Sundial Peak.

In other parts of the Grampians there are also named rock formations. There is Castle Rock in the Victoria Range. In the ount Victory Range, an extension of the central ridge, is a formation of overhanging ledges called the Balconies. At the northern end of the Mt Difficult Range, a semi-circular spur of Mt Staplyton, Hollow Mountain, that erosion has hollowed out on the inner side. It has many formations that were formed by wind erosion that formed arches and open-roofed caverns.

The MacKenzie River has cut the MacKenzie Gorge through the less resistant rock strata, but where the erosion was slowed by more resistant layers waterfalls have formed, resulting in one place in a series of 4 falls. These resistant rock strata are quartzite rocks that were formed intrusions of molten magma.

Vegetation

The rugged nature of these ranges has resulted in a variety of environments with their own microclimate. Over the millions of years since the formation of the ranges the climate of the area changed a number of times. With each change of climatic regime in the surrounding area a new suite of vegetation developed to take advantage of the climate at the time. When the climate changed again, remnants of the vegetation types that had found their way to a suitable part of the ranges remained as relict populations that could could return to their former habitat in the surrounding country whenever the climate they were adapted to returned to the area.

The main vegetation types of the ranges are dry forests and heath woodlands, though there are smaller areas of wet forest, scrublands and savanna woodlands. At least 20 species of plants are endemic to the Grampians, and many others are hundreds to thousands of kilometres from the nearest populations of the same species. Many trees are stunted because of the impoverished, sandy soils of the ranges.

Sources & Further reading

Helen Grasswill & Reg Morrison, Australia, a Timeless Grandeur, Lansdowne, 1981