Geography of the Highlands

PALEOGRAPHY:

Australia is the oldest of continents. After Antarctica, it is the smallest (at 8.5 million square kilometres - 3700kms north to south, and 4000 kms east to west).

It is the only continent containing just one nation (although in the past there were hundreds of smaller aboriginal nations before European settlement: two co-existed here in the Highlands area).

Originally part of the super land mass Gondwanaland some 500 million years ago (Cambrian Period), it was formed after the movement of the earth's tectonic plates, travelling north, then finally separating about 95 million years ago.

The continent is still drifting about 7 cms a year towards Asia - something which saves the airlines a few cups of fuel each year!

Over hundreds of millions of years, various parts of the continent were under the sea - which explains why you can find seashells and marine fossils in rocks on top of present day mountains.

Most of the land under the Highlands is sandstone, therefore once ocean floor. Sandstone is still quarried today in Bundanoon.

About 300 million years ago (Carboniferous Period), glaciers covered part of the eastern shore and ice sheets the south.

The subsequent erosion caused by rivers of molten ice contributed to the current land formation. Coal swamps were laid down in the eastern region during this time (also during the Creataceous Period).

Coal mining in the Highlands at Bundanoon, near Berrima, and Mittagong over 100 years ago, and today at Tahmoor to the north, and in the Illawarra region to the east attest to this. Shale deposits were mined at Joadja at the end of last century, and peat near Berrima, and next to the Wingecarribee Swamp today, although it is possible these deposits were laid down at a later time.

Wingecarribee swamp and peat marshes today.

While the dinosaurs were playing in their Jurassic playground (135-195 million years ago), the great rivers of inland Australia were being laid down.

The flatness of the terrain means most of these flow inland. The rivers and creeks of the Highlands, however, date from more recent times.

During the Cretaceous Period (100-135 million years ago) much of the interior of the continent was covered again by the sea (so the early Australian explorers searching for an inland sea were about 100 million years too late!)

Dense sub-tropical rainforest on the eastern escarpment.

Towards the end of this period the seas subsided, the present coastline of the continent began to appear, and the climate became warmer with extensive sub-tropical rainforests on the south coast. Large areas of this rainforest can be seen today as you travel down the escarpment to the east of the Highlands towards Wollongong and Nowra. Over a century ago the now rich farming lands around Robertson, Kangaloon, and Burrawang were covered by a thick jungle-like scrub (the Yarrawa Brush).

Patches of rainforest and sub-tropical flora can still be found in micro-climate pockets throughout the Highlands.

The ubiquitous Australian scrub and eucalyptus tree landscape was formed only several million years ago. During this time also, the continent was joined to Asia by a land bridge, allowing animal and plant life to travel freely between them.

GEOLOGY:

The Great Dividing Range runs all the way from north to south of the continent along the east coast - the product of geological shear and uplift as the tectonic plate the continent is part of grated against the next in the Pacific Basin. Although the mountains of this Range are quite puny compared with the alps and highlands of Europe (the highest mountain in Australia is only 7316 feet above sea level), the Range rises over 2000 feet abruptly above the eastern coastline.

Mountains near Barrengarry

This does not make this mountain chain young. On the contrary it is one of the oldest mountain chains on earth, like the Australian continent itself, worn down by hundreds of millions of years of erosion.

Most of the Australian continent is flat, except for a few mountain outcrops and ranges here and there - flat all the way from the east to the west coast.

Further to the east - in New Zealand and other islands of the Pacific, and to the north - in Indonesia, these great faults in the earth's crust gives rise to smoking volcanoes and earthquakes.

Mt. Gibraltar

The ancient land mass of Australia harbours no volcanoes. The remains of some however, such as Mt. Gibraltar and Mt. Alexandra in the Highlands, can still be seen. Similarly, there are few earthquakes. Even though there is a minor fault line in the earth's crust which runs from South Australia diagonally northeast across the continent, through the Highlands and on to the coast north of Sydney, tremors are rare. (Evidence of this fault line - rift valley - can be seen more spectacularly at Lake George near Canberra.)

Earth tremors do occur regularly in the Highlands, but so small as usually not to be noticed. On occasions these have registered over 5 on the Richter scale (1961), but have not been as devastating as that which destroyed parts of Newcastle some years ago.

Their existence reminds us nonetheless of the nature of the land on which we sit.

TOPOGRAPHY:

The earliest settlers of the colony of Sydney (1788) gradually took up land to the west until they came up against the solid wall of the Blue Mountains. It took until 1813 until a way was found over these to the interior. Meanwhile, further south - near Camden - the range offered a more gentle rise: from Camden, over the Razorback Range, upwards towards Bargo, then a relatively short climb to the plateau of the Southern Highlands. This route was explored some 15 years earlier than the Blue Mountains crossing. The Southern Highlands is over 2000 feet (700m) above sea level. It sits atop a plateau which straddles the Great Dividing Range.

View over the escarpment to the coast, Robertson.

To its centre it is about 150kms south west of Sydney (along the historic access route) and 80kms from the ocean directly to the east near Wollongong.

Deep river gorges, east of Bundanoon

It is truncated on most of three sides by steep gorges and valleys, making travel near impossible, and to the east by the steep escarpment above Wollongong and the Illawarra region. A line of lesser hills and ridges allows approach from Sydney, and towards the Tablelands to the west, which when discovered, led to the opening of the continent. Dense eucalyptus forests and scrub surround the Highlands. To the east this gives way to sub-tropical rainforest as you travel down the escarpment to the warmer coastline (best seen on a drive down the Macquarie Pass towards Wollongong, or the Meryla Pass to Kangaroo Valley, and on to Nowra).

Today of course you can get here by Freeway from the centre of Sydney in only an hour and a half, not the days it took in earlier times. The freeway passes through on its way towards Canberra, the west of the state, and south to Melbourne. (There is still no freeway over the Blue Mountains.)

Several prominent landforms rise above it - Mt. Gibraltar between Mittagong and Bowral - and Mt. Alexandra and Mt. Jellore to the north of Mittagong. The former two are the remains of volcanic plugs left after the surrounding mountains eroded away. The plateau sits atop sandstone. To the northeast and southeast the steeper valleys carry minor rivers and their tributaries, dammed at the Nepean, Avon and Cordeaux Rivers supplying water to Sydney in the north, and the Shoalhaven River for Nowra in the south.

Lake in the steep gorge of the Nepean River.

The former floodplains of the Wingecarribee (it is now dammed, with little flow) sweep around between Bowral and Kangaloon, to the north of Moss Vale (at Bong Bong - an original site of settlement), through Berrima, past the former settlement of Joadja, westwards towards the Burragorang Valley and the Wollondilly River. Other lesser rivers (Paddys) and creeks join it.

Wingecarribee Flood Plain, looking west.

These flatter lands hold mostly clay soils, and in earliest times were reported to have little vegetation other than grasses and shrubs. Imported grasses, however, were quickly planted here, and became the basis of sheep and cattle grazing. Around these plains are some grey loam soils more suited to pasture. With the availabilty of fertilisers later in the nineteenth century these became productive farming land.

Needless to say, like most of Australia, these soils are thin and land clearing and overproduction have led to erosion in places.

(You can see how thin the topsoils are by looking at the cuttings alongside the freeway - the first few centimetres with grass on top quickly give way to clay and rock underneath.)

The best soils were not used in the first 50 years of settlement. These are rich volcanic soils - the residue of former activity of Mt. Gibraltar. These sweep to the east towards Glenquarry, Kangaloon, and towards Robertson. In former times this was covered in dense jungle-like scrub, no doubt taking advantage of the rich soil. As it was almost impassable, there was little attempt to clear it until the second half of the nineteenth century.

Dense Yarrawa Brush at Robertson.

Red earth soils at Robertson.

When it was cleared it made rich grazing land - mostly for intensive dairying - and was planted with various crops, of which potatoes were one of the most successful. The town of Robertson arose in its midst, still famous for its potatoes, although dairying has been of lesser importance in recent years. You can see the difference in the topography by the dark red soils in this area.

THE LAND TODAY:

Today the dominant impression of the Southern Highlands is of extensive green meadows, and quaint English-style countryside, perched between wild hills and gorges of native scrub. This appearance, however, is due to the land clearing and farming practices of the early settlers. During the earliest settlement over 150 years ago, the Highlands presented a picture of thick, often impenetrable forest and scrub. This gave way to more sparsely treed shrub and grasslands along the floodplains of the Wingecarribee River, which rises in the ranges behind Mt. Gibraltar, and flows inland.

Cows grazing on hedged pastures at Glenquarry.

It is not surprising that the earliest settlers chose these riverways in their earliest expeditions towards Goulburn and the southern interior of the continent, and one of the earliest settlements was placed there (Bong Bong).

Thereafter the settlers proceeded to clear the land, and recreate it in their vision of what they remembered of England. European grasses were sown on the first grazing lands, and European conifers and deciduous trees planted on properties, in towns and backyards.

Several vast pine forests were also planted (Penrose and Belanglo State Forests). These plantings give the area much of the character it has today.

However, you don't have too go far in any direction to find yourself back in the bush of pre-settlement times, and everywhere among the alpine conifers and picturesque deciduous trees of old Europe can be seen the native vegetation.

In more recent times, people have become more conscious of how the land is used, and of the native vegetation and fauna.

Large areas have been luckily preserved in the past - some by design (Morton National Park - which previously had the less pretentious name "Bundanoon Gullies") - and some by default, the vast forests which surround the catchment areas of the dams to the north and east which provide the water supplies to Sydney and the South Coast.

These are easily accessible and can give the modern visitor an insight into the beauty of the original landscape.

Of late, the 'Pinus Radiata' planted in their thousands by earlier nostalgic settlers - especially in townships and gardens - have been recognised as a noxious weed, and the Council is encouraging their removal.

These may have suited the sun-avoiding householders of previous ages, but their distinctly unfriendly habit of poisoning the land around them with acid residue, and their tendency to prolong dampness has made them a nuisance. Most have well exceeded their useful life expectancy of 50 years.

Their removal will allow the more picturesque deciduous trees to flourish, and hopefully encourage the planting of a wider variety of native trees and flora. This will bring the townscape environment closer to that of its surrounding countryside, and encourage the preservation of native bird and animal life. Several nurseries in the area specialise in propagating native plants, and homeowners are beginning to see their usefulness for landscaping. Lessons to be learnt? As you wander around the beautiful Southern Highlands, it helps to be more aware of what you see - even as you gaze towards the horizon from a lookout. Everywhere around you is a story of the origins of the countryside, and of our continent.

Natural vegetation, Belmore - just above the Falls..