Australia's journey continues. Its most recent history has seen it populated with humankind, whose members arrived in two separate rafts. The first arrivals sought to fit into the landscape and saw themselves as part of it. Their touch on the continent was light, and in the 50 000 or more years of their tenure they have experienced significant change, particularly to climate and coastal geography. And they have brought about some change themselves, through hunting and fire.

The second raft brought humans who developed a much more populous presence. Their tenure has been very short and their outlook quite different. They have viewed the continent as a fixed and stable entity, with changes to it squarely in their hands. Their touch has been much more heavy: the built environment, the transformation of landscapes through the application of agriculture and the mass movement of material in mining operations. Their experience has been too short for them to appreciate change wrought by the Earth's system both independent of, and within, the sphere of human influence. In some cases they have been surprised by change completely outside their control – weather events, floods, tidal surges and earthquakes. In many others they have interfered with, and changed, aspects of the Earth's system without a satisfactory understanding of the consequences – for example, mismanagement of groundwater and landscapes, causing their degradation.

Although we are slow to see it, change to Australia is an integral part of its being; this is the essential lesson to learn from the rocks. The surface of the continent is its most transient part and is subject to change on a whole range of timescales, both with direct human help and without it. Understanding the drivers of such change, and the rates at which they apply, and recognising those we can influence, are ongoing challenges.

An appreciation of the national estate, scaled expansively for time and space, is the gift of geology. The discipline also has relevance for change over shorter periods and at local scale, particularly in relation to landscape dynamics and the effective utilisation of the Earth's resources to service the needs of humankind.