What will be the lasting impression made by mankind - 100 million years hence? Jan Zalasiewicz, a lecturer in geology at the University of Leicester, has published a new book looking at the lasting impression likely to be made by mankind.

He takes the perspective of alien explorers arriving on earth - their geologists study the layers of rock, using the many clues to piece together its history over several billion years.

A story unfolds of moving and changing continents, rising and falling oceans, ice ages, and evidence of life going back many millions of years. They grow familiar with its phases of change, the rise of great new ecosystems, and occasional catastrophic collapses of life. But then they stumble on something quite different in a thin layer of rock: a striking signal of climate changes, extinctions and strange movements of wildlife across the planet. Following this trail, decoding clues in the rocks takes them to the petrified remains of cities, and finally to the fossilized bones of those, long dead, who built them.

Dr Zalasiewicz said: "From the perspective of 100 million years in the future – a geologist's view – the reign of humans on Earth would seem very short: we would almost certainly have died out long before then. What footprint will we leave in the rocks? What would have become of our great cities, our roads and tunnels, our cars, our plastic cups in the far distant future? What fossils would we leave behind?

"My study shows how scientists put together clues from the rocks to understand the past, its landscapes and climate, and the nature of the creatures that inhabited it. A thin layer of silt here, a trace formed by a crawling worm there–the clues are often subtle and difficult to read. But by such clues would future geologists – whether hyper-evolved rat or alien visitor – work out our story. My study explores which of our structures are likely to leave traces, and what future explorers might make of us and the impact we made on our environment.

"Looking to the distant future gives us a warning for the present: our activities have already left a significant footprint on the planet, and not a flattering one. It is not too late to limit it. We would not wish to be dubbed by future explorers the 'amazingly clever and utterly foolish two-legged ape'."

Zalasiewicz's book "The Earth After Us: What Legacy Will Humans Leave In The Rocks?" is published by Oxford University Press. For more information, see: http://www.oup.com/uk/catalogue/?ci=9780199214976