PROJECT
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Western Plains history
Victoria’s Western Plains extend westward from Melbourne almost to the border with South Australia. On this former lava
field are many of the state’s volcanic landforms and features, including many scoria cones, over 80 lava tubes, and
volcanoes such as Mt Elephant, Mt Napier and
Mt Noorat.(Scoria is a dark lava formed when gases
escape through magma. It looks a bit like pumice
stone, but is denser.) Most of this landscape formed
during the last five million years. The last eruption
occurred at least 20 000 years ago.
Although hundreds of volcanoes have erupted in the
region, none were active for any length of time. Most
produced a runny lava (through central and side vents)
that spread out across the region’s limestone base,
sometimes up to 50 kilometres away. Over time, these
flows covered one another in places, building up rocky
layers up to 60 metres thick in some spots. Where
flows crossed one another, rocky rises formed; where
flows sagged, lakes and swamps eventually formed in
the depressions.
Some of the volcanic eruptions were more
explosive, often occurring when rising hot magma or gas came in contact with water-saturated rocks. Fine-grained debris
and circular craters — evidence of this sort of eruption — are more common in the area around the towns of Colac and
Camperdown.
Over time, the once barren volcanic landscape of the Western Plains region has weathered, more so in places where
eruptions occurred a long time ago. Weathering has enabled vegetation such as grasses to take hold.
Use this worksheet and the source listed as a Reference to complete the following.
1.
Name three agents of erosion.
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2.
What is a lava tube? Draw a simple diagram below your explanation to depict how it is formed.
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© John Wiley & Sons Australia, Ltd 2004
2004-09-west-plains.pdf
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PROJECT
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3.
Which of the following landforms are examples of places where more material is being eroded than deposited?
Explain why this is the case in each instance.
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Lord Howe Island
Big Ben on Heard Island
Mt Etna (Sicily)
Belougery Spire (New South Wales)
Mt Nyiragongo (Republic of Congo, Africa)
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4.
Name two characteristics typical of most former volcanic eruptions in the Western Plains region.
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5.
What might a volcanologist studying the region reasonably assume if he/she comes across (a) a low-lying
swampland, (b) a rocky raised area and (c) a circular crater?
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Reference:
SOSE Alive 3, pp. 105, 116–17, 120 ▪ SOSE Alive Geography 2, pp. 8–9, 20–1, 24
© John Wiley & Sons Australia, Ltd 2004
2004-09-west-plains.pdf
(Page 2 of 2)