This one is interesting in that it is mainstream and explains that we
really don't know what is going on deep inside the earth's interior. It
is all speculation. To wit: "¶ Or something novel and bizarre is
going on, as yet undetermined."
/Bob
http://www.nytimes.com/2012/05/29/science/earths-core-the-enigma-1800-mi\
les-below-us.html?nl=todaysheadlines&emc=edit_th_20120529
<http://www.nytimes.com/2012/05/29/science/earths-core-the-enigma-1800-m\
iles-below-us.html?nl=todaysheadlines&emc=edit_th_20120529> The Enigma
1,800 Miles Below Us [0] Sebastian Raymond/New Line Cinema
DEEP THOUGHTS Jules Verne's classic "A Journey to the Center of the
Earth" has inspired several film versions, including one in 2008.
By NATALIE ANGIER
<http://topics.nytimes.com/top/reference/timestopics/people/a/natalie_an\
gier/index.html> Published: May 28, 2012
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As if the inside story of our planet weren't already the ultimate
potboiler, a host of new findings has just turned the heat up past
Stygian.
Multimedia [0] Interactive Feature
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A diagram of the Earth's center as a giant ball of fire from the 1678
book "Subterranean World."
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pagewanted=all> 20th Century Fox
A poster for the 1959 film version of the Jules Verne classic.
Geologists have long known thatEarth
<http://topics.nytimes.com/top/news/science/topics/earth_planet/index.ht\
ml?inline=nyt-classifier> 's core, some 1,800 miles beneath our
feet, is a dense, chemically doped ball of iron roughly the size of Mars
and every bit as alien. It's a place where pressures bear down with
the weight of 3.5 million atmospheres, like 3.5 million skies falling at
once on your head, and where temperatures reach 10,000 degrees
Fahrenheit as hot as the surface of the Sun. It's a place
where the term "ironclad agreement" has no meaning, since iron
can't even agree with itself on what form to take. It's a fluid,
it's a solid, it's twisting and spiraling like liquid confetti.
Researchers have also known that Earth's inner Martian makes its
outer portions look and feel like home. The core's heat helps
animate the giant jigsaw puzzle of tectonic plates floating far above
it, to build up mountains and gouge out seabeds. At the same time, the
jostling of core iron generates Earth' magnetic field, which blocks
dangerous cosmic radiation, guides terrestrial wanderers and brightens
northern skies with scarves of auroral lights.
Now it turns out that existing models of the core, for all their drama,
may not be dramatic enough. Reporting recently in the journal Nature,
Dario Alfè of University College London and his colleagues presented
evidence that iron in the outer layers of the core
<http://www.nature.com/nature/journal/v485/n7398/abs/nature11031.html>
is frittering away heat through the wasteful process called conduction
at two to three times the rate of previous estimates.
The theoretical consequences of this discrepancy are far-reaching. The
scientists say something else must be going on in Earth's depths to
account for the missing thermal energy in their calculations. They and
others offer these possibilities:
¶ The core holds a much bigger stash of radioactive material than
anyone had suspected, and its decay is giving off heat.
¶ The iron of the innermost core is solidifying at a startlingly fast
clip and releasing the latent heat of crystallization in the process.
¶ The chemical interactions among the iron alloys of the core and the
rocky silicates of the overlying mantle are much fiercer and more
energetic than previously believed.
¶ Or something novel and bizarre is going on, as yet undetermined.
"From what I can tell, people are excited" by the report, Dr.
Alfè said. "They see there might be a new mechanism going on they
didn't think about before."
Researchers elsewhere have discovered a host of other anomalies and
surprises. They've found indications that the inner core is rotating
slightly faster than the rest of the planet, although geologists
disagree on the size of that rotational difference and on how, exactly,
the core manages to resist being gravitationally locked to the
surrounding mantle.
Miaki Ishii <http://www.seismology.harvard.edu/ishii.html> and her
colleagues at Harvard have proposed that the core is more of a
Matryoshka doll than standard two-part renderings would have it. Not
only is there an outer core of liquid iron encircling a Moon-size inner
core of solidified iron, Dr. Ishii said, but seismic data indicate that
nested within the inner core is another distinct layer they call the
innermost core: a structure some 375 miles in diameter that may well be
almost pure iron, with other elements squeezed out. Against this giant
jewel even Jules Verne's middle-Earth mastodons and ichthyosaurs
would be pretty thin gruel.
Core researchers acknowledge that their elusive subject can be
challenging, and they might be tempted to throw tantrums save for the
fact that the Earth does it for them. Most of what is known about the
core comes from studying seismic waves generated by earthquakes.
As John Vidale of the University of Washington explained, most
earthquakes originate in the upper 30 miles of the globe (as do many
volcanoes), and no seismic source has been detected below 500 miles. But
the quakes' energy waves radiate across the planet, detectably
passing through the core.
Granted, some temblors are more revealing than others. "I prefer
deep earthquakes when I'm doing a study," Dr. Ishii said.
"The waves from deep earthquakes are typically sharper and
cleaner."
Dr. Ishii and other researchers have also combed through seismic data
from the human equivalent of earthquakes the underground testing
of nuclear weapons carried out in the mid- to late 20th century. The
Russian explosions in particular, she said, "are a remarkably
telling data set," adding that with bombs, unlike earthquakes, the
precise epicenter is known.
Some researchers seek to simulate core conditions on a small, fleeting
scale: balancing a sample of iron alloy on a diamond tip, for example,
and then subjecting it to intense pressure by shooting it with a bullet.
Others rely on complex computer models. Everybody cites a famous paper
in Nature in 2003 by David J. Stevenson, a planetary scientist at
Caltech, who waggishly suggested that a very thin, long crack be
propagated in the Earth
<http://www.nature.com/nature/journal/v423/n6937/full/423239a.html> down
to the core, through which a probe in a liquid iron alloy could be sent
in.
"Oh, the things we could learn, if only we had unlimited
resources," Dr. Ishii sighed.
The core does leave faint but readable marks on the surface, by way of
the magnetic field that loops out from the vast chthonic geodynamo of
swirling iron, permeating the planet and reaching thousands of miles
into space. Magnetic particles trapped in neat alignment in rocks reveal
that the field, and presumably the core structures that generate it, has
been around for well over 3 billion of Earth's 4.5 billion years.
For reasons that remain mysterious, the field has a funny habit of
flipping. Every 100,000 to a million years or more, the north-south
orientation of the magnetosphere reverses, an event often preceded by an
overall weakening of the field. As it turns out, the strength of our
current north-pointing field, which has been in place for nearly 800,000
years, has dropped by about 10 percent in the past century, suggesting
we may be headed toward a polarity switch. Not to worry: Even if it were
to start tomorrow, those of us alive today will be so many particles of
dust before the great compass flip-flop is through.
The portrait of the core emerging from recent studies is structured and
wild, parts of it riven with more weather than the sky. Earth assumed
its basic layered effect as it gravitationally formed from the rich,
chunky loam of the young solar system, with the heaviest ingredients,
like iron and nickel, migrating toward the center and lighter rocky
material bobbing above.
Traces of light, abundant elements that bond readily with iron were
pulled coreward, too, and scientists are trying to figure out which mix
of oxygen, sulfur or other impurities might best match the seismic data
and computer models. Distinct boundaries of state or substance
distinguish the different layers between the elastic rock of the
mantle and the iron liquid of the outer core, and between the liquid
outer core and the solid inner core.
The core accounts for only one-sixth of the volume of the Earth but
one-third of its mass, the great bulk of iron maintained in liquid form
by the core's hellish heat. "Liquid" in this case
doesn't mean molten like lava. "If you could put on your safety
gloves and stick your hands into the outer core, it would run through
your fingers like water," said Bruce Buffett, a geologist at the
University of California, Berkeley.
"The viscosity is so low and the scale of the outer core so
large," Dr. Buffett added, "that the role of turbulence is a
relevant feature in how it flows. Think planetary atmosphere, or large
jet streams." Only in the inner core does pressure win out over
temperature, and the iron solidify.
The core's thermal bounty is thought to be overwhelmingly
primordial, left over from the planet's gravitational formation and
mostly trapped inside by the rocky muffler of the mantle. Yet as the hot
Earth orbits relentlessly through frigid space, the core can't help
but obey the second law of thermodynamics and gradually shed some of its
stored heat.
The heat can be transferred through two basic pathways: conducted
straight outward, the way heat travels along a frying pan, or convected
out in plumes, the way hot air rises in the atmosphere or soup bubbles
in a pot.
Conduction is considered a wasted or even boring form of energy transfer
heat moves, but the Earth does not. Convection, by contrast, is
potentially industrious. Convection currents are what ripple through the
mantle and shuffle around the tectonic plates, and convection stokes the
geodynamo that yields our switching field.
In their report in Nature, Dr. Alfè and his colleagues used powerful
computers and basic considerations of atomic behavior to calculate the
properties of iron and iron alloys under the presumed conditions of the
core. They concluded that the core was losing two to three times as much
heat to conduction as previously believed, which would leave too little
thermal energy to account for the convective forces that power the
Earth's geodynamo. Hence the need to consider possible sources of
additional heat, like stores of radioactive potassium or thorium, or a
fast-crystallizing inner core.
Dr. Buffett suggests that water on the surface may also help Earth
balance its thermal budget, by slightly weakening the Earth's
rocky plates and making them more readily churned and recycled in a
vigorous, sustainable convective stew.
Life needs water, and maybe its planet does, too.
A version of this article appeared in print on May 29, 2012, on page D1
of the New York edition with the headline: The Enigma 1,800 Miles Below
Us.
[Non-text portions of this message have been removed]