Werribee Plain facts for kids

The Werribee Plain is a large, flat area of land located west-southwest of Melbourne, Victoria, Australia. This plain is known for its very flat, wide-open spaces. Sometimes, you'll see tall features like the You Yangs, which are rocky hills made of granite, and a few small, extinct volcanoes. The Werribee Plain is part of the much bigger Western District Volcanic Plains, which stretch from Melbourne all the way to the South Australian border.

How the Werribee Plain Was Formed

Volcanoes and Lava Flows

The flat lands of the Werribee Plain were mostly created by ancient Volcanoes. These volcanoes started erupting lava about 4.5 million years ago! The most recent eruptions happened only about 10,000 years ago.

There are more than 400 old craters and vents (places where lava came out) mapped across these plains. Even though these individual volcanoes are no longer active (they are "extinct"), the whole area is considered "dormant." This means it's like a sleeping giant, and new eruptions could still happen someday.

The Story of the You Yangs

The You Yangs are different from the rest of the plain. They are made of a type of rock called granite. This granite formed a very long time ago, during a period called the Devonian. It started as hot, melted rock (called magma) that pushed its way up into other rocks underground.

The magma cooled down and became solid rock before it reached the surface, so it didn't cause any volcanic eruptions. Because it cooled very slowly, large white crystals of a mineral called feldspar formed. You can still see these crystals in the granite rocks of the You Yangs today.

Ancient Volcanic Islands

The closest volcanoes to the You Yangs are called the Anakies. You can see them as three low hills in the distance to the west. These hills have craters at their tops and once sent lava flowing across the plains south of the You Yangs.

Lava also flowed from other low volcanoes, like Bald Hill and Spring Hill, which are 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 looked like granite islands sticking out of a huge sea of flowing lava!