by futurist Richard Worzel, C.F.A.
The Earth is a complex system. Indeed, it is a series of interlocking, overlapping, complex systems, and such systems often affect each other in surprising ways. Accordingly, although at first it may seem strange to say that climate change will increase both the number of earthquakes and volcanoes, that actually is the case. Here’s how it works:
Although to us, the Earth’s crust and upper mantle seem solid, from a geological perspective they are actually quite elastic, rather like a trampoline. This is especially true when you consider that the surface of the Earth, including the continents, floats on tectonic plates, which cause the phenomenon popularly called “continental drift”. Parts of the Earth’s surface, including sections of the continents, actually move, and around the edges of these plates, bits are both sucked down below the surface, and squeezed up from underneath, as well as scraping along each other’s edges, as happens with the San Andreas fault in California. That’s why it looks as if eastern South America fits into western Africa: because at one time it did, before the plates they’re on drifted apart.
Where climate change comes into the picture is that it changes something called the “isostatic equilibrium” of the Earth’s surface. Isostasy is the force that balances gravity’s books: when something shifts its weight, creating more weight in one place, it is balanced by something somewhere else being pushed up in another place. (Here’s a link to Wikipedia on the subject.)
Let’s go back to the trampoline metaphor now. If you put a big block of ice in the middle of the trampoline, it will push it down. And ice is very heavy; a one-meter cube of ice weighs more than a ton. As it melts, the trampoline will gradually spring back. And that’s what will happen as the Earth’s glaciers melt, the water runs off into the oceans, and the weight of the glaciers is redistributed: the crust and mantle will spring up in another area. We know that this happens, because, for example, that’s why there are earthquakes in Quebec, where there are no major fault lines. In the last ice age, Quebec was covered in more than three kilometers of ice. When the ice melted as the ice age ended, the Earth sprang back, freed from the load, and that process of adjustment continues to this day. (Ten thousand years, the period of time since the last ice age, is not very long in geological terms.)
As glaciers melt, therefore, it upsets the balance in the Earth’s crust and mantle; because weight shifts from the land where the glaciers were, down into the oceans as the melted ice runs off. As a result, there is less weight on the land, and more weight in the oceans. This will create what geologists call an “isostatic rebound”, and according to studies of the Earth’s geologic history, that can make the Earth’s tectonic plates shift. This not only creates earthquakes, but volcanoes as well, because bubbles of magma trapped underground (magma is molten rock beneath the Earth’s surface) act like bottles of seltzer. When the Earth shifts, they act like someone has shaken the seltzer bottles. Indeed, geophysicist Allen Glazner of the University of North Carolina recently commented that “It’s unavoidable that glacial retreat will induce tectonic activity.” He goes on to say, “Recent findings reinforce the idea that the solid earth and the climate are inextricably linked.”
The geologic record shows that this has happened in the past. When the glaciers retreated after the last ice age, it triggered a wave of volcanic eruptions, notably in Scandinavia, the Mediterranean, Antarctica, and eastern California. As well, the incidence of major earthquakes has risen over the last three decades, as shown in this chart from data assembled by the website dlindquist.com:
Annual Number of Earthquakes, Magnitude 6 or Higher
Like most real data, although there’s a trend visible, it’s not straight up. But if you mathematically smooth the data to take some of the dramatic ups and downs out, you get a much clearer picture, from the same website:
So we will see more earthquakes and more volcanoes as a result of the melting of today’s glaciers. Among the areas that have been identified as possible targets for this kind of natural disaster include Alaska, the Andes, the Swiss Alps, the southern Alps of New Zealand, the Rocky Mountains in the U.S. and Canada, the Himalayas, and the edges of Greenland.
It’s going to be an exciting time, but “exciting” doesn’t actually mean “fun”, does it?
© Copyright, IF Research, February 2011.
 Begley, Sharon; “How Melting Glaciers Alter Earth’s Surface, Spur Quakes, Volcanoes”, Wall Street Journal, June 9, 2006, p.A11.