Gaia Vince concludes her journey through the geological age humans have launched. After climate change and mass extinction, she now explores how cities, manufactured artefacts (from plastic bottles to mobile phones) and chemical pollution might become ‘fossilised’ and incorporated into the geological record. Some are bound to survive in crushed form for the rest of the Earth’s existence. Any distant-future geologist would recognise them as strange features unique in the planet’s 4 billion year rock record, and as evidence of a planetary shift into the new time period, which today’s geologists call the Anthropocene.