At first glance, the world seems a well-ordered and predictable place. The apparent order and stability of our day-to-day existence has allowed farming and civilisation to develop, regulated by the simple, customary changes of day and night, the tides and the seasons. At the scale of human lives, it seems that rivers flow steadily to the sea, mountains stay put at the horizon and sea level remains within the limits of the local tidal range.
It soon became clear to the earliest peoples that this vision of stability and predictability is dangerously unreliable. The most obvious departure from stability occurs because of changes in the weather. Extreme conditions are experienced only a few times in a person’s lifetime: storms can drive the sea inland, flooding the coastal plains, while heavy rains cause rivers to break their banks and even change course, destroying floodplain farms. These catastrophes are common enough that ancient civilisations learned to take precautions against them by building coastal defences, consolidating river banks or (more often) by simply avoiding flood-prone areas.
Bad weather is a minor problem in comparison with the truly rare disasters like the most powerful earthquakes and their associated tsunami (“tidal waves”), volcanic eruptions and major landslides. Such events are experienced more frequently in some parts of the world but generally affect us less than once per generation. Ancient peoples learnt to avoid living in the most disaster-prone areas but could only invent and pray to a pantheon of gods to try to avoid the unexpected. The ruins of Santorini and Pompeii witness the effectiveness of this approach.
On the longest time scale experienced by Man, the greatest disasters are recorded by distant tribal memories. Tales of great floods which destroyed whole civilisations probably refer to the rapid melting of continental ice-sheets which began about 12,000 years ago, since when world sealevel has risen by some 400 feet (130m). Fossilised seashells are found on the highest mountainsides, suggesting still greater upheavals in prehistoric times. The rarest global catastrophes, the impact of large asteroids or comets, or the breakdown of the Earth’s protective magnetic field, have probably never been experienced by humans.
To some extent the study of the Earth’s surface, the processes that affect it and the history of such events has been driven by our need to understand and predict dangerous changes in our own environment. The second motivation has been to find useful natural resources, be they flint deposits or oil fields. But perhaps the greatest drive has been simple curiosity, the search for an explanation of our prehistory and for knowledge of the workings and history of our world.