Silurian: 443–416 million years ago

The land turns green

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Silurian marine environment.
Image: Karen Carr
Source: Collection of the Indiana State Museum and Historic Sites

420 million years ago.
Image: Ron Blakey. Altered by Cally Bennet and Fons VandenBerg
Source: Colorado Plateau Geosystems

Silurian

Until plants evolved, the landscape was barren. Without plants to stabilise the soil, the Earth was bare and scoured by erosion. A green fringe on the water’s edge began a slow transformation; a small number of plants developed a revolutionary adaptation – vascularity, or the ability to transport water and nutrients through a network of specialised tissue.

These early vascular plants were the first to grow on land, and Baragwanathia, from Victoria, was one of the first leaf-bearing plants known. Land plants, although very low-growing, provided shade, shelter and food, inviting invertebrates to follow into a new world of opportunity.

In the oceans, corals formed expansive reefs while sea-lilies and trilobites thrived. The first jawed fish evolved, and became active predators as well as being prey for other animals. Sea-scorpions and cephalopods were the largest predators in the seas, and some sea-scorpions even ventured onto land.

Australia was part of the supercontinent Gondwana, near the equator with a warm climate. ‘Victoria’ continued to be formed by sedimentation, mountain building and volcanism. Near the end of the Silurian Period, intense heating of the crust beneath Victoria ‘sweated’ gold from deeply buried volcanic rocks into super-hot salty water. This water moved upwards until, near the surface, the gold crystallised out with quartz. This process continued at intervals for another 100 million years, making Victoria one of the world’s richest gold provinces.