Australia’s geological history spans billions of years, with the landmass once part of the ancient supercontinents Rodinia and Gondwana. Around 35 million years ago, Australia separated from Antarctica and began drifting northwards, a slow but continuous process that shaped its current form. About 8,000 years ago, rising sea levels separated the Australian mainland from New Guinea, and Tasmania was cut off roughly 6,000 years ago, marking a dramatic shift in the land’s geography.

Geologically, Australia lies well within the Australian tectonic plate, providing a relatively stable foundation. Unlike other regions that experience frequent mountain building, active volcanoes, or tectonic faults, Australia’s mainland remains largely unchanged. However, the Australian plate is slowly moving north-northeast at about 6 to 7 cm per year, colliding with the Eurasian and Pacific plates. These intratectonic forces result in seismic activity, with 18 recorded earthquakes of a magnitude greater than 6 between 1901 and 2017. One of the most notable seismic events was the Newcastle earthquake in 1989, which tragically claimed 13 lives.

While volcanic activity on the mainland ceased thousands of years ago, evidence of past eruptions persists in Aboriginal place names and creation stories. The most recent volcanic activity occurred around 4,600 years ago, and today, active volcanoes can be found in the remote Heard Island and McDonald Islands.

The geological structure of Australia consists of a combination of ancient and relatively young rocks. The country’s continental crust was formed in three primary cycles, with the oldest rocks dating back to the Archaean period. In Western Australia, some of the surface rocks are more than 3.7 billion years old, and in South Australia, rocks are over 3.1 billion years old. The oldest zircon crystals discovered on Earth, dating back 4.4 billion years, were found in Western Australia. Despite its ancient foundations, around 80% of Australia’s land is covered by sedimentary rocks and regolith that are less than 250 million years old, marking a dynamic but gradual geological evolution.

Australia’s geologically stable yet seismically active nature makes it a fascinating case study in Earth’s tectonic processes and provides insight into the planet's long-term geological transformation.