Victoria is an Australian state, situated at the southern end of the Great Dividing Range. The Great Dividing Range stretches along the east coast of the continent and terminates near the Victorian city of

Ballarat Ballarat ( ) is a city in the Central Highlands of Victoria, Australia. At the 2021 Census, Ballarat had a population of 116,201, making it the third largest city in Victoria. Estimated resident population, 30 June 2018. Within months of Vi ...

west of the capital Melbourne, though the nearby Grampians may be considered to be the final part of the range. The highest mountains in Victoria (just under 2,000 m) are the

Victorian Alps The Victorian Alps, also known locally as the High Country, is a large mountain system in the southeastern Australian state of Victoria. Occupying the majority of eastern Victoria, it is the southwestern half of the Australian Alps (the othe ...

, located in the northeast of the state. The northwest of the state is mostly Cainozoic rocks while the southeast is primarily made up of

Palaeozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...

rocks. There have been no discoveries of

Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of th ...

rocks in Victoria. The low flat northwest of the state that borders the

Murray River The Murray River (in South Australia: River Murray) ( Ngarrindjeri: ''Millewa'', Yorta Yorta: ''Tongala'') is a river in Southeastern Australia. It is Australia's longest river at extent. Its tributaries include five of the next six longe ...

was once the bed of an ancient sea and the land is much afflicted with

salinity Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...

. Saline drainage from Victorian land is one of the sources of the salinity problem in the Murray–Darling River system. Commercial

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quanti ...

evaporation is undertaken near Swan Hill. Central and western Victoria comprise world-class vein-hosted gold deposits, hosted mostly in the extensive

Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. ...

turbidite A turbidite is the geologic deposit of a turbidity current, which is a type of amalgamation of fluidal and sediment gravity flow responsible for distributing vast amounts of clastic sediment into the deep ocean. Sequencing Turbidites w ...

s. The southeast of the state has enormous

brown coal Lignite, often referred to as brown coal, is a soft, brown, combustible, sedimentary rock formed from naturally compressed peat. It has a carbon content around 25–35%, and is considered the lowest rank of coal due to its relatively low heat ...

fields.

Volcanism

There is an area of extensive

volcanism Volcanism, vulcanism or volcanicity is the phenomenon of eruption of molten rock (magma) onto the Earth#Surface, surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics, and volcanic gases erupt through a break in the su ...

in central and southwestern Victoria, where there are numerous

volcano A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates ...

es and volcanic lakes. The Western Victorian Volcanic Plains are the third largest in the world after the

Deccan The large Deccan Plateau in southern India is located between the Western Ghats and the Eastern Ghats, and is loosely defined as the peninsular region between these ranges that is south of the Narmada river. To the north, it is bounded by t ...

in western

India India, officially the Republic of India ( Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the ...

, and the

Snake River The Snake River is a major river of the greater Pacific Northwest region in the United States. At long, it is the largest tributary of the Columbia River, in turn, the largest North American river that empties into the Pacific Ocean. The Snak ...

Plateau in

Idaho Idaho ( ) is a state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Montana and W ...

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...

. The most recent volcanic activity was at Mt Eccles, which last erupted a few thousand years ago, making it an active volcanic region. Large

basalt Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% of a ...

ic lava flows are present on the western side of Melbourne and in the southwest of the state.

Neoproterozoic to early Carboniferous

This period is covered by the recent Geological Survey of Victoria publication ''The Tasman Fold Belt System in Victoria''. The sequence of events associated with the building of southeastern Australia reveals that mineralization and magmatic processes are intimately linked with the

tectonic Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents ...

development of the region. The history is dominated by east–west compression of predominantly oceanic

sedimentary Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...

and

igneous rock Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or l ...

s and their resultant

fold Fold, folding or foldable may refer to: Arts, entertainment, and media * ''Fold'' (album), the debut release by Australian rock band Epicure *Fold (poker), in the game of poker, to discard one's hand and forfeit interest in the current pot *Above ...

ing, faulting and uplift. Recently, it has become increasingly apparent that major north–south movements have also been involved in constructing eastern Australia. The

basement is traversed by

thrust fault A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. If ...

s more or less parallel to the north–south structural grain. The largest faults separate rocks with different ages and structural histories, and subdivide Victoria into three main structural rankings consisting of twofold belts (Delamerian and Lachlan), two terranes in the Lachlan Fold Belt (Whitelaw and Benambra), and ten structural zones (Glenelg, Grampians-Stavely, Stawell, Bendigo, Melbourne, Tabberabbera, Omeo, Deddick, Kuark, Mallacoota).

Moyston Fault

Island Archway, Great Ocean Rd, Victoria, Australia - Nov 08

The Moyston Fault is the most important fault as it forms the terrane boundary between the Delamerian and Lachlan fold belts. These twofold belts show important differences. The Delamerian Fold Belt is mainly composed of Neoproterozoic-

Cambrian The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ag ...

rocks and was deformed in the Late Cambrian Delamerian

Orogeny Orogeny is a mountain building process. An orogeny is an event that takes place at a convergent plate margin when plate motion compresses the margin. An '' orogenic belt'' or ''orogen'' develops as the compressed plate crumples and is uplifted ...

whereas the Lachlan Fold Belt contains mainly Cambrian-

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, w ...

rocks with the main deformations occurring in the late

to early Carboniferous interval. The first regional deformation to affect the Lachlan Fold Belt was the Benambran Orogeny, about 450

MYA Mya may refer to: Brands and product names * Mya (program), an intelligent personal assistant created by Motorola * Mya (TV channel), an Italian Television channel * Midwest Young Artists, a comprehensive youth music program Codes * Burmese ...

, after the Delamerian Orogeny.

Granite Granite () is a coarse-grained ( phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies und ...

s comprise 20% of the total exposed area of the Lachlan Fold Belt and fall within an age range of 440 to 350 MYA. Volcanics associated with the granites are also widespread and cover an additional 5%. Blocks of older crust consisting of Neoproterozoic-Cambrian rocks, such as the Selwyn Block in central Victoria, were deformed during the late Cambrian Tyennan Orogeny prior to being incorporated into the Lachlan Fold Belt.

Baragwanath Transform

The second major structural break in Victoria is the Baragwanath Transform, which occurs along the eastern side of the Selwyn Block. This

transform fault A transform fault or transform boundary, is a fault along a plate boundary where the motion is predominantly horizontal. It ends abruptly where it connects to another plate boundary, either another transform, a spreading ridge, or a subducti ...

divides the Lachlan Fold Belt into two terranes, the Whitelaw Terrane to the west and the Benambra Terrane to the east. The main difference between these is that orogen-parallel (north-south) transport was more prevalent in the Benambra Terrane, whereas convergent east–west transport orthogonal to the orogen was dominant in the Whitelaw Terrane.

References

External links

*
GeoVIC - Victorian Government Geospatial Application
*

Western Victorian Volcanic Plains Western may refer to: Places *Western, Nebraska, a village in the US *Western, New York, a town in the US *Western Creek, Tasmania, a locality in Australia *Western Junction, Tasmania, a locality in Australia *Western world, countries that id ...