Werribee Plain
Encyclopedia
The Werribee Plain is an extensive low-lying area of flat land located WSW of Melbourne
, Victoria, Australia. The plains are notable for their extensive, flat, featureless spans, interspersed by the occasional vertical feature, such as the You Yangs
, a series of granite
ridges, and several small extinct volcanoes. The Werribee Plain forms part of the vast Western District Volcanic Plains that extend from Melbourne to the South Australia
n border.
es began erupting lava flows about 4.5 million years ago, and the youngest eruptions are only about 10,000 years old. There are over 400 mapped craters and vents on the plains. While all these individual volcanoes are extinct, the volcanic field itself is only dormant, so tnew eruptions are possible at any time.
The granite that forms the You Yangs
was originally a mass of magma that worked its way up into the surrounding sedimentary rocks during a period of geological time known as the Devonian
, The magma crystallised before it reached the surface, so it did not produce any volcanic activity. Instead, a very slow cooling rate allowed many large white crystals of feldspar to form. These can be seen in many of the granite outcrops throughout the ranges.
The nearest volcanoes to the You Yangs are the Anakies, which appear as three low hills on the western horizon. These all have summit craters and provided lava flows for the plains south of the You Yangs. There were also flows from the low volcanoes of Bald Hill and Spring Hill to the north of the You Yangs. When these volcanoes were active, probably between 2 and 3 million years ago, the You Yangs would have been granite islands in a sea of lava.
Melbourne
Melbourne is the capital and most populous city in the state of Victoria, and the second most populous city in Australia. The Melbourne City Centre is the hub of the greater metropolitan area and the Census statistical division—of which "Melbourne" is the common name. As of June 2009, the greater...
, Victoria, Australia. The plains are notable for their extensive, flat, featureless spans, interspersed by the occasional vertical feature, such as the You Yangs
You Yangs
The You Yangs are a series of granite ridges that rise to 364m above the Werribee Plain approximately 55km south west of Melbourne and 22km north east of Geelong, in Victoria, Australia. The main ridge runs roughly N-S for about 9 km, with a lower extension running for about 15 km to the west...
, a series of granite
Granite
Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...
ridges, and several small extinct volcanoes. The Werribee Plain forms part of the vast Western District Volcanic Plains that extend from Melbourne to the South Australia
South Australia
South Australia is a state of Australia in the southern central part of the country. It covers some of the most arid parts of the continent; with a total land area of , it is the fourth largest of Australia's six states and two territories.South Australia shares borders with all of the mainland...
n border.
Geology
VolcanoVolcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...
es began erupting lava flows about 4.5 million years ago, and the youngest eruptions are only about 10,000 years old. There are over 400 mapped craters and vents on the plains. While all these individual volcanoes are extinct, the volcanic field itself is only dormant, so tnew eruptions are possible at any time.
The granite that forms the You Yangs
You Yangs
The You Yangs are a series of granite ridges that rise to 364m above the Werribee Plain approximately 55km south west of Melbourne and 22km north east of Geelong, in Victoria, Australia. The main ridge runs roughly N-S for about 9 km, with a lower extension running for about 15 km to the west...
was originally a mass of magma that worked its way up into the surrounding sedimentary rocks during a period of geological time known as the Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
, The magma crystallised before it reached the surface, so it did not produce any volcanic activity. Instead, a very slow cooling rate allowed many large white crystals of feldspar to form. These can be seen in many of the granite outcrops throughout the ranges.
The nearest volcanoes to the You Yangs are the Anakies, which appear as three low hills on the western horizon. These all have summit craters and provided lava flows for the plains south of the You Yangs. There were also flows from the low volcanoes of Bald Hill and Spring Hill to the north of the You Yangs. When these volcanoes were active, probably between 2 and 3 million years ago, the You Yangs would have been granite islands in a sea of lava.