Comment: The Earth fights back

Now we discover that not only are the oceans and the atmosphere conspiring against us, bringing baking temperatures, more powerful storms, floods and ever-climbing sea levels, but the crust beneath our feet seems likely to join in too. …

Several times in the past couple of million years the ice left its polar fastnesses and headed towards the equator, covering much of the world's continents in ice sheets over a kilometre thick, and sucking water from the oceans in order to do so. …

Each time the ice retreated, sea levels shot up again, sometimes at rates as high as several metres a century. In the mid 1990s, as part of a study funded by the European Union, we discovered that in the Mediterranean region there was a close correlation between how quickly sea levels went up and down during the last ice age and the level of explosive activity at volcanoes in Italy and Greece. …

But how can rising sea levels cause volcanoes to erupt? The answer lies in the enormous mass of the water pouring into the ocean basins from the retreating ice sheets. The addition of over a hundred metres depth of water to the continental margins and marine island chains, where over 60% of the world's active volcanoes reside, seems to be sufficient to load and bend the underlying crust.

This in turn squeezes out any magma that happens to be hanging around waiting for an excuse to erupt. It may well be that a much smaller rise can trigger an eruption if a volcano is critically poised and ready to blow. …

As sea levels climb higher so a response from the world's volcanoes becomes ever more likely, and perhaps not just from volcanoes. Loading of the continental margins could activate faults, triggering increased numbers of earthquakes, which in turn could spawn giant submarine landslides. …

The Earth is responding as a single, integrated system to climate change driven by human activities. Global warming is not just a matter of warmer weather, more floods or stronger hurricanes, but is also a wake-up call to Terra Firma. It may be no coincidence that one outcome of increased volcanic activity is likely to be a period of falling temperatures, as a veil of volcanic dust and gas reduces the amount of solar radiation reaching the surface. Maybe the Earth is trying to tell us something. It really would be worth listening before it is too late.

Professor Bill McGuire, Guardian Unlimited

Professor McGuire is Director of the Benfield UCL Hazard Research Centre. His book, 'Surviving Armageddon: Solutions For a Threatened Planet' is published by OUP. His next book, 'What Everyone Should Know About the Future of Our Planet: And What We Can Do About It', is published by Orion in January next year.