There are those who bemoan what they see as Australia’s boring countryside — no majestic snow-capped mountain ranges, no vast valleys with giant plunging waterfalls, no roaring rivers surging towards the sea, only sweeping seemingly featureless panoramas, dry salty mud sinks, lazy crawling rivers that seem to ooze across the landscape rather than race with life towards the sea. Compared to other continents, Australia appears to be boring, tired and unattractive.
How you choose to interpret the reality of this land is up to the individual, and in this age of the world wide web and seemingly instantaneous and cheap global travel, comparisons are easy to make, but there are good and solid reasons for the way our terrain is structured.
Australia is, at its core, a very old land. That seems, on the surface, to be a fatuous statement. Isn’t all land old? The answer is no.
New land is being created all the time. On a smaller scale volcanic action constantly pushes up new material, building new terra firma to be colonised by plants and animals.
On a grander scale, tectonic action pushes together smaller parcels of land (a process called rafting) into larger packages, builds offshore ridges to create near-shore troughs which fill with sediments eroded from mountains and, quite simply, sea floor is lifted to become dry land. All of this can take a long time — tens of millions of years — but in the grand scale of Australia’s history that’s small beer.
Australia’s eastern margin — east of a line roughly drawn north-south through Broken Hill and Mt Isa — and parts of its southern coastal fringe are the products of the latter processes — rafting, uplift and sediment infill — over the past 400 million years, but head to the west and north-west and we are driving over a land that’s been moving around over the Earth’s outer surface for thousands of millions of years.
The Australia that we see today is pretty much as it was about 100 million years ago, just with added erosion.
This area in the far west and north is Australia’s craton. A craton is defined as “a large stable block of the Earth's crust forming the nucleus of a continent”. The word stable is important here in defining the look of Australia today. The minimal or absent mountains, the lazy winding rivers, the vast flat salt lakes are signs that this land is the consequence of a lot of erosion over a long period of time; that the once mighty mountain ranges have been slowly but inexorably ground down and the fine dust and particles has been washed into the lowlands to leave us with as close to a flat landscape as we can imagine in most places.
The Flinders Ranges in central South Australia are an excellent example of this. These were once at the height of the Himalayan Mountains, but 400 million years of erosion had brought them down almost to ground level by about 60 million years ago. Relatively minor uplift since then has raised them to their present modest, if still spectacular, levels. There are a number of other similar eroded stumps of mountain ranges scattered across Australia.
To be technically accurate, the Australian craton is in reality a series of smaller cratons that have been welded together a long time ago, but they all carry the same message — that we mostly live on a very ancient landscape.
The ‘ancient’ adjective here is underlined by the presence of the oldest rocks on Earth, with discoveries made earlier this year in the Jack Hills of central Western Australia putting the components of rocks from there at 4.4 billion (that’s 4400 million!) years of age. These small zircon crystals were formed a hundred or so million years after cosmic dust and scraps of rocky materials coalesced to form our planet.
The oldest traces of ‘biotic life’, at 4.1 billion years of age, were found not far away. That even the most basic forms of life appeared so soon after the formation of the planet, when it would have been extremely hostile for any molecular structure we might recognise as ‘life’, is a pretty good indication that at least the basic building blocks of life came from ‘out there’.
Also implicit in the seemingly featureless expanse of the Australian landscape is the relative absence of tectonic activity. You can read that to say that we don’t experience much in the way of volcanic activity, certainly nothing like that which occurs in much of the rest of the Earth. Australia is very stable in that sense. The most recent volcanic activity in Australia was at Mt Gambier about 6000 years ago, and there were volcanoes down the East Coast and in Victoria that were active geologically quite recently, but these were largely related to the passage of Australia over a ‘hot spot’ which essentially blasted small holes in the continent as we moved north. That hot spot is now somewhere under Bass Straight.
While we don’t have massive mountains, we also don’t have the catastrophic experience of huge earthquakes, such as are suffered in the western United States, western South America, southern Europe and Turkey, China, India, Japan, Indonesia or New Zealand. Those are the by-products of the forces which create those majestic snow-capped mountains and roaring rivers and waterfalls that look so nice on foreign postcards.
We do suffer smaller earthquakes on occasion due to minor faults in the crust beneath the surface and, as Australia is being driven northwards at a rate of 7cm per year by plate tectonics, we are pushing up against crustal plates to our north thus creating stresses in our nation’s structure that result in these minor shifts. Be grateful that those are the worst aspects we experience of the sorts of huge internal forces that underpin so much of the Earth’s surface.
By ensuring that we have a ‘flat and featureless’ landscape, the absence of those massive tectonic forces has ensured we have been left with massive deposits of iron ore and other natural resources which have underpinned our prosperity over the past 50 years and will probably do so long into the future.