The Turmoil Within : Deep below Earth’s surface, surprised scientists have found huge shifting formations and tornado-like magnetic fields.

It comes as no surprise to Southern Californians that solid Earth moves. But until recently, geologists believed that these periodic rumblings were mostly skin-deep.

Outbreaks such as earthquakes, volcanoes and violent weather were confined to the surface, like a bad complexion. Hidden beneath the layers of crust and mantle, they felt, the planet had an inner serenity.

New insights into the world down under, however, have unearthed an unexpected hotbed of activity:

* Thousands of miles down, continent-sized formations build up and break apart, much as they do on the surface.

* Currents of rock rise, fall and churn like weather patterns--albeit at a slower pace.

* Iron crystals rain toward the core, piling into drifts like snow.

* Magnetic field lines twisted into cyclones somehow produce the neat North and South magnetic poles used by navigators around the world to set their compasses. Every hundred thousand years or so, the poles flip--and South becomes North.

All these discoveries are rearranging geologists’ ideas about how the Earth works, and how it came to be. Evidence is now overwhelming that the planet did not come gently into being, but rather was part of a primordial storm throughout the solar system that blew the crust off Mercury, slammed into Venus hard enough to reverse its spin, and ripped the moon out of the Earth like Adam’s rib.

Today, the leftover heat of that violent era--still buried deep in the Earth’s core--drives mountain building, volcanoes and earthquakes.

“It’s a major paradigm shift,” said UC Berkeley geophysicist Raymond Jeanloz, who notes that as recently as the 1970s, geologists did not accept the idea that continents drift around on the mantle’s Plasticine sea.

Jeanloz, a MacArthur “genius” Fellow, specializes in what he argues is the most geologically active region on Earth. It can be found, he said, “about three days’ drive straight down, if you could do it.”

Jeanloz’s research leads him to believe that the thin layer between the Earth’s core and the overlying mantle is the most dramatic structure on the planet.

Although the core lies a mere 1,740 miles from the surface, it is a world as remote and inaccessible as the planet Pluto. Digging a hole to the center isn’t an option because the pressure gets so intense even a few miles down that the Earth instantly heals itself, filling in any hole before it gets very deep.

A far more successful source of information has been seismic waves created by earthquakes or bomb blasts and detected by increasingly sophisticated networks of seismometers (many of them developed by the military to monitor secret underground nuclear tests).

Jeanloz decided to take a different tack, however. If he couldn’t get to the core, why not bring the core to the surface?

In his lab at Berkeley, Jeanloz re-creates the high-pressure conditions at the core-mantle boundary by squeezing together minerals between the points of gem-quality diamonds. The diamonds are hard enough to withstand pressures over 1 million times atmospheric pressure, and transparent enough to transmit ultraviolet and infrared radiation as well as visible light.

When Jeanloz squeezes his “nutcracker,” the pressure is concentrated into the tiny points of the diamond anvils. He can get the sample up to 1,000 Earth atmospheres with his bare hands. To get to 1 million atmospheres, he needs “a very special tool,” which turns out to be a small wrench.

Another laser heats the sample up to thousands of degrees in a fraction of a second. “Essentially, what we get is a puddle of rock,” Jeanloz said.

Of course, to replicate conditions at the core of the Earth, researchers also need to know the ingredients that go into making the inner planet. The crust is well-understood, consisting mostly of silicon and oxygen. From seismic measurements, geologists have determined that the core is solid iron, surrounded by a liquid iron mixture rather like steel.

But the mantle in between is far more exotic. In fact, it’s a crystal structure that does not exist on the surface.

The material is something like diamond, in that it is a crystal form of an ordinary substance. Diamond is carbon that has been cooked in the high-pressure environment deep in the Earth. The mantle material is made up of ordinary rocks that get melted and squeezed into a remarkably regular structure with unusual properties. It is a solid, but it flows. “That seems weird to physicists,” Jeanloz said.

To make tests on a sample, Jeanloz and his lab mates maneuver a tiny bit of iron into the diamond press along with a bit of crystal sprinkled with ruby dust. Then they squeeze it to see what happens.

In effect, they are doing a new kind of chemistry, in which chemical bonds between molecules are rearranged not by heat or reactants, but by simple brute force. “We squish them together, and get new states of matter,” he said.

What they have discovered is surprising: There is active chemistry going on in this subterranean alchemy. That has important implications for the study of the planet’s enigmatic magnetic field--which Einstein described as the Earth’s greatest mystery, said Jeanloz.

By all accounts, the Earth should not make such a good magnet. Things are simply too hot in the core to sustain a magnetic field.

Rather, geologists believe that flowing currents surrounding the solid core generate a magnetic field the way electric current flowing through a wire creates an electromagnet. The trouble is that geological studies of surface magnetism have turned up convincing evidence that the fields are turbulent with tornado-like eddies, and flip at semi-regular intervals.

“We think the mantle rock is dissolving into the iron of the outer core,” Jeanloz said. “If these chemical reactions do take place, then it’s likely that the magnetic field gets perturbed by these metallic zones deep in the mantle.”

The chemical reactions, in other words, may well be involved in directing the behavior of the magnetic field. And the behavior of that field may ultimately have an influence on the evolution of life.

Researchers know that the magnetic field plays a central role in screening the denizens of Earth from harmful radiation. When the field flips, that protective cover begins to fall apart, letting the solar wind with its highly charged particles through to Earth.

Periods of very weak or erratic magnetic fields could have spelled death to thousands of species.

Even if Jeanloz’s speculations turn out to be premature, it is unlikely that people will ever again view the third planet from the sun as a static globe floating quietly in space.

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Pressure cooker

To reproduce the pressures and temperatures of deep earth, material is squeezed and heated in a metal- foil gasket between the tips of two diamond anvils. A laser beam can be focused through the diamond to heat the sample.

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The D” Layer

Geologists think the most active area on Earth may be the tin boundary between the planet’ lower mantle and outer core. Known as the D” layer, it is a rough terraine where continents form and break up and active chemistry takes place.

Source: Scientific American