Australia – The Eastern Highlands
In most of the maps of Australia the so-called Great Dividing Range is eminently represented. The eastern highlands of Australia determine the watershed between the coastal side and the one that goes west to Lake Eyre and the mouth of the Murray. But the heights, examined closely, show that they do not constitute a chain at all, but a series of separate elements of very different origin. The watershed coincides with an orographic line important only in the area of relatively recent basaltic effusions of Queensland, in the granite massif of the New England Mountains and in the large area of Pliocene basalts of Victoria, which certainly filled pre-existing valleys and lowlands, forming a watershed of quite recent origin. In the long intermediate stretches of these isolated orographic districts the watershed runs on relief lines barely marked on the general level: and in many stretches its extremely irregular and sinuous course indicates its complex and not very remote origin. Parallel to the current watershed line, there is a strip of other lands almost coinciding with the coastline, formed by an approximately continuous series of granite masses, which goes from Cape York to Tasmania: in all probability they formed the watershed main during the Pliocene, before the uplift that moved it to the west.
In northern Queensland there is one of the most interesting high regions of Australia: the Atherton plateau, the only one, worthy of the name, which rises in the tropical climatic zone with considerable rainfall. It is therefore fertile, with abundant waters and also rich in useful minerals, so that it is of great importance for tropical settlements. Its area above 600 m. however, it does not exceed 39,000 sq km. The plateau gradually rises eastwards to the summit of M. Bartle Frère (1657 m.), Which almost dominates the coast and is the highest point of Queensland. The heavy rains, as the plateau is in the path of the trade winds, and the backlash of the recent uplift have caused a strong regressive erosion by coastal streams such as the Barron, Johnstone, the Mulgrave so that the landscape, which features frequent waterfalls, is among the most picturesque in Australia. In recent times the coast has undergone many fluctuations: a series of coastal plains of very recent origin indicates an uplift, of which the great gorges and waterfalls are also evident signs. But the prevailing characteristic is given by a lowering movement: the coral reliefs of the Great Barrier probably constitute only the superficial part of a submerged coastal margin; even the festoons of islands, so common along the coast, clearly indicate the general decline.
According to usprivateschoolsfinder, the Clarke Range at Mackay rises only to a narrow extent above 600m. and some of the basaltic plateaus along the so-called Dividing Range barely reach this level. Many small lakes near the Tropic, Buchanan, Galilee (32 km. Long), Dunn, Mueller, seem to be the remains of ancient rivers flowing through the current watershed. Perhaps present-day Burdekin also headed west into the Thomson River through these depressions. The hilly region of Darling is also mainly composed of basalts with steep slopes to the east: a series of volcanic cones of the Upper Tertiary make up the Glass House Mountains. Similar cones are found further north in the Peak Range.
The New England plateau constitutes the northernmost part of the eastern highlands in New South Wales. It is the largest if not the highest in Australia, presenting, above 900 m., A territory about 300 km long., 65 wide. Three mountain nodes between Tenterfield and Armidale (Ben Lomond, Capoompeta and Chandler’s Peak) rise to 1540m, while a high spur called the Snowy, or Snowy Mountain, and the Barrington Peaks further south reach about the same height. According to Andrews, the plateau would represent a surface eroded almost to sea level and then raised unevenly to form the current fractured and deformed surface. There are three elevated levels of the ancient surface: the Guyra penepiano at a height of about 1300 m., The Mole penepiano at 1200 m. and the Stannifer penepian at about 975. The coastal rivers have carved back gorges or cañons (upstream of the Macleay river) about 900 m deep. Three volcanic groups are part of the plateau: the trachytic cones of the group called Monti Nandewar Range between Armidale and Narrabri; a similar group south of Narrabri, forming the Warrumbungle Range, which reaches 914m; and the chain of the Liverpool Mountains, capped with basalts, which unites this group to the main massif of the plateau. An important topographical feature is found south of the Mt of New England in the Cassilis Gate, a large pass far below 600m: it is the most notable depression in the mountains between Brisbane and Melbourne, but no railway line uses it; it appears to be partly due to erosion and partly to tectonic movements.
A fractured area, called Passo del Lago Giorgio, separates the Monti Azzurri from the southern highlands. Two small lake basins owe their origin to fractures with rejection and the consequent obstruction of watercourses: Lake Bathurst and Lake Giorgio, 32 km long, generally almost dry. The presence of picturesque gorges on the Molonglo River near Canberra and Burrinjuck on the Murrumbidgee River shows the recent origin of these river valleys. South of Lake Giorgio a series of horstsor fractured plates brought to various heights constitutes the Australian Alps (v.), culminating in M. Kosciusko. But the mountains north and east of Cooma are generally not considered to be parts of the Australian Alps. From the artificial lake of Burrinjuck to the head of the Murrumbidgee river, a mountainous area extends which reaches 1909 m. in M. Bimberi and has snow-capped peaks during the winter months. A parallel horst towards south-east forms the Tindery Mountains (1400 m.): Between the two lines of hills, a plain at about 620 m. bears the name of Monaro Range; it is crossed by the Snowy river and is limited to the east by a rather steep escarpment (erroneously referred to in the papers as the Illawarra chain) which descends to about 450 m. on the narrow coastal plain. The straight nature of the coast, parallel to the escarpment, betrays the fracture surgery; a similar origin can also be attributed to the coast from the Shoalhaven River estuary to Sydney.
Victoria’s topography includes three main elements: the eastern highlands, structurally akin to those of New South Wales; the northern plains which are properly part of the Murray basin already considered; and a flat, depressed area in the southwestern part of the state called the Great Valley.
The notable change of direction in the main axis of the mountain range beyond M. Kosciusko is not due to differences in structure. The other lands of Victoria also appear to be made up of horsts, massive parallels, which follow from north to south across the state. The highest are in E. (Bogong, 1984 m., Hotham, 1860 m.), While the main pass is the “Porta” of Omeo which separates the southern dependencies of the Kosciusko group from the Bogong plateau: the valleys of Mitta and of the Tambo River form there a line of depression across the other lands, in which is also Lake Omeo. South of the Bogong rise the high floors of Dargo (1370 m.) And towards the N. rises Mount Buffalo (1720 m.), Dominating the Murray plains with steep sides. The edges of this raised penepiano have been deeply eroded by rivers: especially the Goulburn has carved out a very wide and deep valley. Towards the west the mountain becomes lower on average, but the Howitt, Wellington and Torbreck mountains still exceed 1500 m.: further on it descends rapidly to the “Gate” of Kilmore at only 300 meters above sea level. The heights of Victoria, to the west of the pass, consist of a penepiano degrading from M. Macedon (1000 m.) towards the south-west: the level is about 600 m. in Ballarat, 300 in Ararat and 160 in Hamilton. Cracks similar in origin and direction to those of Kosciusko determine the Pyrenees (987 m.) And the Grampians (1166 m.). The whole western lowland complex south of the watershed was covered by basaltic lavas which are part of the Great Victoria Valley, at about 150 meters above sea level. Small volcanic cones are common everywhere (M. Elephant, 394 m.; M. Noorat and Tower Hill). Various lakes are also scattered in the depressions of this basaltic lava plane, and perhaps Port Phillip can also be considered a submerged strip of the Great Valley,
Tasmania is part of the eastern highlands, which indeed presents itself throughout its territory as an alpine fragment of them. It essentially consists of sediments from the lower Paleozoic resting on granite, which in the center and east house important carboniferous deposits covered in turn by basic eruptive rocks. The dominant feature in the topography is the central plateau, inclined from NW. to the SE., in which the basin of the river Derwent develops. This plateau seems to be a horst, while the more depressed region to the north and east seems to have undergone a lowering in steps which has left evident steep cliffs (tiers). The highest peaks are given by the mountains Cradle (1545m), Eldon (1459m), Field West (1439m) and Ironstone (1443m). The highest peak of the island, however, is the Law’s Peak (1573 m.) In the Ben Lomond plateau. The deep gorges of the rivers on the western side (King, Franklin, and Denison), the great lakes of the central plateau (Great Lake, Arthur, Sorell), the truncated aspect of the eastern coasts, are all features demonstrating that the present topography of the the island had its fulfillment relatively recently. Moraines and other ice age traces have been described for the Cradle, Field West, Anna and various others.