Landforms in Victoria Description

Landforms of Victoria Description

To help explain the landforms, it is interesting to compare the poster with the following diagram.

Alan Willocks, Manager Geophysics, and Fons VandenBerg, geologist, Energy & Minerals, DPI provided the following information:

Many of Victoria’s landforms owe their origin to the break-up of Gondwana, an ancient super-continent that once comprised Australia, Antarctica, Africa, South America and India. The break-up commenced some 100 million years ago and currently Australia is still drifting northwards at the rate of about 10 centimetres per year.

In the upland regions, the landscapes have little to do with the origin of the rocks—instead it is due to dissection by the many streams. The dissection pattern reflects the ‘grain’ of these various rocks, which in turn reflects folding, faulting and other features that formed well after the rocks themselves were made. In the lowland regions, by contrast, the landforms are often a direct consequence of how the rocks formed and range from flood plains to dune-fields and from lava fields to ancient beach ridges.

Upland regions

Great Dividing Range
Uplift of the Great Dividing Range, which forms Victoria’s backbone, began about 80 million years ago and was mostly completed several tens of millions of years ago, although small amounts of uplift are continuing to the present day. The eastern portion was uplifted much more than the western part. The mountains consist of a great variety of ancient rock types (mudstones and sandstone deposited in the sea and on land, lava flows and other volcanic rocks, and granites) that formed during the Palaeozoic era (550 to 340 million years ago).

Southern Highlands
The Southern Highlands (Otway and Strzelecki ranges) are about the same age as the Great Dividing Range but are made up of much younger rocks—sandstones and mudstones that were deposited 120 to 100 million years ago, when dinosaurs still roamed the earth.

Lowland regions

Northern Plains
The northern plains lie above the Murray Basin, a large saucer-shaped continental basin that began to form about 55 million years ago. The basin contains a mixture of marine clays and limestones that formed at times when the basin was inundated by the sea, and terrestrial clay, sand and gravel deposited by rivers and derived from the Great Dividing Range. The surface of the northern plain reflects this mixed origin: the Riverine Plain in the east consists of clay and silt deposited by rivers, whereas in the Wimmera Plain, long low ridges of sand were deposited during retreat of the sea which last inundated the basin about 5 million years ago. Large dunefields cover this marine sand in the Little and Big deserts. Numerous small and large lakes are due to wind deflation and have low crescentic dunes on their eastern sides.

Southern lowlands
The landscapes of the southern lowlands are more variable, reflecting their different origins. The Millicent Plain is very similar to the Wimmera Plain in origin and landscape. The West Victorian Plain, also known as the Western Victorian Volcanic Plain, is a volcanic landscape dominated by lava flows and dotted with small volcanoes. It is young, having formed in the last five million years. Shallow lakes are common here and mark the sites of explosive volcanoes. The Gippsland Plain is a riverine plain covered with sand and gravel that came out of the highlands and was deposited by rivers.

This document was last reviewed on 26/03/2004.