The largest known volcanic eruption in history was not that of Krakatoa but one that took place on another Indonesian island 68 years earlier. It ripped apart Mount Tambora on Sumbawa, not far from Bali, on April 10, 1815. More than 60,000 people died during, or in the aftermath of, the eruption - the greatest loss of life ever recorded in a volcanic disaster. In addition to a vast quantity of pumice, the eruption disgorged 60 million tonnes of sulphur gases. These transformed into tiny sulphuric acid droplets, which spread across the planet high in the atmosphere, where they acted as a veil to incoming sunlight for at least two years. Brutally cold weather hit the northeastern US, and maritime provinces of Canada and Europe in 1816, which came to be known as the "year without a summer". Poor harvests ensued, drastically pushing up grain prices on both sides of the Atlantic. At the same time, the demographic and political upheavals following the end of the Napoleonic Wars exacerbated the agricultural crisis, leading to famine and disease, widespread begging and vagrancy, rioting and large-scale emigration (notably from New England).
The historian John Post characterised the period as the "last great subsistence crisis of the Western World". He went on to suggest that social and economic reversals experienced in these years initiated a political shift to the Right, especially in France and Germany. Thus he saw the political reaction of European governments to the epidemics, commercial depression, unemployment and social disturbances as the end of a chain of events that began with the eruption of a volcano in a remote part of Indonesia. While the details can be debated, there remain strong arguments connecting natural disasters to abrupt changes in society.
The magnitude of the Tambora eruption, though formidable in historical context, is rather meagre compared with ancient and prehistoric volcanic cataclysms. For example, the eruption of Toba in Sumatra (Indonesia has more than its fair share of volcanism) some 74,000 years ago was between 50 and 100 times larger. There is little doubt that it had profound impacts on the contemporary atmosphere and climate, and it may have triggered a millennium of global cooling.
In addition to experiencing mighty eruptions, Earth has been bombarded through geological time by comets and asteroids. One impact, 65 million years ago, arguably resulted in the demise of the dinosaurs, part of the "mass extinction" event written in the fossil record at the boundary between the Cretaceous and Tertiary Periods. The threat of future "deep impacts" prompted Lord Sainsbury, Britain's Science Minister, to establish a task force in 2000 to review the hazard and report on potential mitigation strategies.
There seems, therefore, to be a widespread recognition today that global catastrophes can change the course of evolution. But it was not always so.
In Perilous Planet Earth , Trevor Palmer charts the development of ideas on the nature and biological impacts of abrupt environmental change. The scope of the book is ambitious, spanning, among other topics, religion, mythology, palaeoanthropology, genetics and geological and planetary science - from Noah to Nasa in 30 chapters. But Palmer, head of the department of life sciences at Nottingham Trent University, weaves the material around his central themes of changing views on change and the evidence used to support arguments in favour of catastrophist versus gradualist schools of thought.
The book is divided into two parts. "Catastrophism: the story of its decline and fall - and resurrection" engages with the history of debate on floods, earthquakes, eruptions, bolide impacts and their relationships to evolution and extinction and to the waxing and waning of civilisations.
Charles Lyell's Principles of Geology , published in three volumes between 1830 and 1833, was particularly influential in establishing the grip of gradualist thought that Palmer argues prevailed until about 1980. One of the principles became known as uniformitarianism - the idea that geological processes occurred in the same fashion and at the same rate in the past as they do in the present. Lyell drew evidence from various sources, including stratigraphy, and this passage from his book, which considers the volcanic landscape around the Bay of Naples, conveys the essence of his doctrine:
"Nothing seems wanting or redundant; every part of the picture is in such perfect harmony with the rest that the whole has the appearance of having been called into existence by a single effort of creative power. Yet what other result could we have anticipated if nature has ever been governed by the same laws?"
Among more recent developments are findings in molecular genetics and palaeontology that contradict the paradigm of gradual change: geological evidence for a massive bolide impact at the time of the Cretaceous-Tertiary mass extinction; and archaeological findings that point to rapid environmental change as the culprit for the collapse of ancient societies.
In the shorter, second part of the book, "Catastrophes and the history of life on Earth", Palmer reviews some of these ideas. His message is that the causes, nature and extent of past catastrophes need to be understood to evaluate future risks, and that interdisciplinary research and collaboration is key to this process.
Generally, Palmer manages to steer even-handedly through the opposing territories of catastrophist and gradualist paradigms and, in doing so, illuminates one of the most enduring currents of human thought.
Clive Oppenheimer is reader in volcanology and remote sensing, Cambridge University.
Perilous Planet Earth: Catastrophes and Catastrophism through the Ages
Author - Trevor Palmer
Publisher - Cambridge University Press
Pages - 522
Price - £45.00
ISBN - 0 521 81928 8