A Dynamic Earth's Core? A Self-Correcting Earth Order?

[S]top and think how strange it is that the inner core [of the Earth], imperviously locked away since the creation of the world, may yet be added to the long list of other solid-looking things, such as the Himalayas and the Atlantic Ocean and the planet itself, that are in some ways better understood not as places, but as processes.

--"Greenview: the unsolid Earth," The Economist on-line (8.5.10)

Most of us don't know much about the earth's core, except that it's a hard ball of iron or something, fixed and unchanging as metal usually is. But researchers are now saying that's probably not true; it does change. And more, molten iron migrates into one side of the core's 800 mile diameter, cools, solidifies but continues to move very slowly in the same direction, and approximately 80 million years later migrates out the other side back into a molten state. And the core is very slowly getting larger. Pretty amazing. But I'll let the article explain how:

[I]t feels as though the harder scientists look at the world, the fewer islands of stability they find...A study published this week in Nature bears out that trend in a spectacular way. At the centre of the Earth, below the mountains and the oceans and the thin, brittle crust, below the stony, slow-flowing mantle and the roiling outer core of liquid iron, is a solid inner core. If anything about the planet looked unlikely to partake in a process of endless recycling, you might think this ball of metal, 1,200 kilometres across, squeezed from every direction by a planet's worth of weight, would be it—a dense static hub about which all else turns.

Scientists have known for some time that this inner core is not unchanging. But they had thought that it changed in only one direction—that it simply grew bigger. The Earth is growing cooler as it loses the heat trapped in its creation and generated by radioactive elements within it. It is in fact this cooling which powers the slow circulation of the mantle, and through that the endless remaking of the surface through plate tectonics. As things cool down, the liquid outer core freezes into the solid inner core. It is thought that this process leads the inner core to grow larger at a rate of roughly 30 centimetres a century.

The remarkable new idea...is that this slow growth is a net effect, the residual left over when a greater rate of freezing is offset by a rate of melting almost as large. This notion follows from the hitherto unexplored idea that the spherical inner core is very slightly offset from the planet's centre of mass, so that one side—the western side, as it happens—is slightly lower than the other. On the lower side the pressure is greater, and liquid iron freezes solid. On the higher side the pressure is less, and solid iron melts.

The net effect of this asymmetry, should it persist, would be what the authors call a "convective translation": iron that joins the core in the west will slowly move through it until it melts off in the east.

But what is just as amazing is the fact that so many things about the earth--more than we had reason to believe or examine--are dynamic, self-adjusting, even self-correcting in so many ways. And it suggests an integrated, mutually supportive and responsive planetary whole, an order that assures overall planetary stability and longevity. From the article:

This model may be able to explain various oddities about the inner core—such as the fact that seismic waves pass through it differently when headed north-south than when going east-west—and its surroundings, including the existence of a peculiarly dense fluid layer just above it. It is possible that this new behaviour may have implications beyond the core; that it might explain details of the way that the outer core circulates, and thus the ways in which the Earth's magnetic field changes over time. Once the world is seen as a set of cycles rather than of things it is easier to imagine interesting ways for them to mesh like cogs. The carbon cycle influences the rate at which mountains weather down into seas, the deep circulation of ocean waters helps govern the ebb and flow of ice sheets, and so on.

That said, even if further evidence backs it up, the idea that the inner core is in a continuous cycle of self recreation probably won't matter that much to the landscapes and ecosystems doing similar things 5,000 kilometres further out. The effect is more one of underlining an aesthetic, or even an ideology, of the planet as an engine of ceaseless self-stabilising change. Such an ideology may serve as a useful guide to dealing with the unavoidable impacts that a large technological civilisation must have on the planet it inhabits: while caution counsels minimising such impacts, a sense of how the planet works suggests that making sure its natural systems can deal with them, that they can become part of the flow, could matter just as much.

Does that suggest too much? I don't know, but I don't think so. What appears clear by now is that we owe more respect and care to the earth, air and water, the environment that contains, nurtures and sustains us. For it has always been too easy and self-serving for various interests to dismiss concerns with humanity's damage to the environment and its ecosystems--and often with the half-justified declaration that the environment is strong, resilient and self-healing, that it naturally absorbs and compensates for its minor mistreatments by mankind. And to some extent, this is true.

But there are limits to the damage it can absorb and still adequately support human life and society as we know it. Yes, it can and will self-adjust and self-correct, to be sure. But if the damage is extensive enough, the correction and healing could take a long time--even centuries? millennia?--and we, or life as we know it, may not survive that dramatic a healing process and the time that it takes. But topics and research like this, along with all the other Earth-science knowledge and implications, do take us closer to the information and understanding needed to make more confident, better substantiated statements about what level of harm the environment can bear and still nurture and sustain its fragile human population.