Sunday, June 26, 2016

What Did Earth's Ancient Magnetic Field Look Like?

An illustration of ancient Earth's magnetic field compared to the modern magnetic field, courtesy of Peter Driscoll.

New work from Carnegie’s Peter Driscoll suggests Earth’s ancient magnetic field was significantly different than the present day field, originating from several poles rather than the familiar two. It is published in Geophysical Research Letters. Earth generates a strong magnetic field extending from the core out into space that shields the atmosphere and deflects harmful high-energy particles from the Sun and the cosmos. Without it, our planet would be bombarded by cosmic radiation, and life on Earth’s surface might not exist. The motion of liquid iron in Earth’s outer core drives a phenomenon called the geodynamo, which creates Earth’s magnetic field. This motion is driven by the loss of heat from the core and the solidification of the inner core.

But the planet’s inner core was not always solid. What effect did the initial solidification of the inner core have on the magnetic field? Figuring out when it happened and how the field responded has created a particularly vexing and elusive problem for those trying to understand our planet’s geologic evolution, a problem that Driscoll set out to resolve.

Here’s the issue: Scientists are able to reconstruct the planet’s magnetic record through analysis of ancient rocks that still bear a signature of the magnetic polarity of the era in which they were formed. This record suggests that the field has been active and dipolar—having two poles—through much of our planet’s history. The geological record also doesn’t show much evidence for major changes in the intensity of the ancient magnetic field over the past 4 billion years. A critical exception is in the Neoproterozoic Era, 0.5 to 1 billion years ago, where gaps in the intensity record and anomalous directions exist. Could this exception be explained by a major event like the solidification of the planet’s inner core? 

In order to address this question, Driscoll modeled the planet’s thermal history going back 4.5 billion years. His models indicate that the inner core should have begun to solidify around 650 million years ago. Using further 3-D dynamo simulations, which model the generation of magnetic field by turbulent fluid motions, Driscoll looked more carefully at the expected changes in the magnetic field over this period.

“What I found was a surprising amount of variability,” Driscoll said. “These new models do not support the assumption of a stable dipole field at all times, contrary to what we’d previously believed.”

His results showed that around 1 billion years ago, Earth could have transitioned from a modern-looking field, having a “strong” magnetic field with two opposite poles in the north and south of the planet, to having a “weak” magnetic field that fluctuated wildly in terms of intensity and direction and originated from several poles. Then, shortly after the predicted timing of the core solidification event, Driscoll’s dynamo simulations predict that Earth’s magnetic field transitioned back to a “strong,” two-pole one.

“These findings could offer an explanation for the bizarre fluctuations in magnetic field direction seen in the geologic record around 600 to 700 million years ago,” Driscoll added. “And there are widespread implications for such dramatic field changes.”

Overall, the findings have major implications for Earth’s thermal and magnetic history, particularly when it comes to how magnetic measurements are used to reconstruct continental motions and ancient climates. Driscoll’s modeling and simulations will have to be compared with future data gleaned from high quality magnetized rocks to assess the viability of the new hypothesis.

1 comment:

  1. Space is permanence, otherwise it is not space!!!
    Only absolute emptiness of space is a condition of complete rest, in fact because there is nothing to move, it is the absolute Foundation that never changes.
    Only the absolute emptiness of the space is eternal, of what she did not happen, unlike all the temporary content that fills it.
    Only the absolute emptiness of the space is infinite and has no limit, precisely because it does not have its own composition, which could denote its limit. Space can be infinite only in a single full capacity, otherwise it is not infinity.
    Only the absolute emptiness of the space is completely transparent, because it has its own structure and composition, so to see her - it is impossible, but you can always understand, because without it this World is impossible, nothing is impossible to replace something else.
    Absolute emptiness and space are inseparable concepts the same, the same for all full-scale space which is not dependent on human notions.
    The argument that space and absolute emptiness is a different definition is wrong, and different idea - is there a void in space, or there is no void in space, says the insolvency of a uniform definition = what can be a space.
    Replace the absolute void to something else is impossible, a fact!
    Only absolute emptiness no limit.
    Only absolute emptiness - has no internal limit to the minimum, that is, in fact, nothing can be never-ending in the micro scale, and replace the minimality of the void to something else impossible.
    Only absolute emptiness - has no external limit to the maximum, that is, in fact, nothing can be never-ending in the macro scale and replace the maximality of emptiness, something else also impossible.
    Absolute emptiness is the fundamental constant which determines the space in values of zero and infinity to form a logical understanding of the unchanging basis of all creation.
    Multidirectional distinction between micro and macro scale specifies the amount of space and everything that fills them.
    Everything that exists, everything that we see, pervades, it is the absolute void of space, and not something else!
    Everything that fills the space, has an external and an internal limit!
    The space has definite means and has no limit, but has a major difference from the lack of a limit in minimum to no limit at the maximum, with the possibility of obtaining any center separating in their never-ending boundaries of the two opposites.
    That is total void space has no physical resistance, and makes it impossible to stop and makes to move all that fills it, from the air molecules, to planets, Stars and Galaxies.
    Why it is impossible to create an absolute vacuum, and always turns out just the vacuum? - Elementary!
    All bodies, all objects constantly emit part of their energy in space, some more than others, but there are no material structures that did not share its energy with a spatial void. Therefore, any material that makes up the wall of the sphere, from which is removed the air will still be filled with the energy of the atoms of the walls, so there will almost always be created, though of different densities, but only the vacuum.
    But, the absolute void, can still be obtained artificially, in a closed sphere, in General it is simple, you only need to make the energy of the atoms, molecular structures, spheres, move back from the scope, and it is 100% possible!!!
    When this happens, and it necessarily ever will, all the talk about the emptiness and the idea of space and its energy is changed, as when something has changed ideas about a flat Earth.
    Space - absolutely - everything else is relativity!