revolutions book

Oxford University Press

Revolutions that made the Earth introduces the concept of a very few critical revolutions in Earth history.

Revolutions in Earth History

Between about  800 and 542 million years ago in the Neoproterozoic Era, the modern Earth system was born. Out of the turmoil of 'snowball Earth' glaciations and a rise in atmospheric oxygen, came the first animals forming familiar ecosystems. The group at Exeter have been seeking to understand the causes and consequences of this revolution in Earth history as part of the multi-disciplinary Life & the Planet research project, funded by NERC - see the project website for more information.

Perturbation of the Earth System at the Proterozoic-Phanerozoic transition and the resilience of the biosphere

Charles Darwin's great dilemma was why complex life in the form of fossil animals appear so abruptly in rocks around 520 million years ago (Ma), in what is widely known as the Cambrian explosion. During recent decades, exceptionally preserved animal fossils have been found throughout the Cambrian Period, which began 20 million years earlier, and arguably even through the entire, preceding Ediacaran Period, which directly followed the worldwide 'Snowball Earth' glaciations (~715 - 635 Ma). Most of these exceptional deposits were discovered in South China, which possesses the best preserved and dated geological record of the marine environment for this time. In this genuinely collaborative UK-China project, the aim is to use the South China rock archives to construct a much higher resolution, four-dimensional (temporal-spatial) picture of the evolutionary history of the earliest animals and their environment.

The project aims to address three central scientific questions: 1) How did the coupled biogeochemical cycles of C, O, N, P and S change during these evolutionary radiations?; 2) Did environmental factors, such as oxygen levels, rather than biological drivers, such as the emergence of specific animal traits, determine the trajectory of evolutionary change?; and 3) Did the rise of animals increase the biosphere's resilience against perturbations? This last question has relevance to today's biosphere, as the modern Earth system and its stabilising feedbacks arose during this key interval. By studying it in more detail, and establishing temporal relationships and causality between key events, we can find out how the modern Earth system is structured, including which biological traits are key to its continued climatic and ecosystem stability.