Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Key to the Nature of Earth’s Mysterious Core Found Beneath Arctic Ice

17.10.2002


In the high Canadian Arctic, researchers at the University of Rochester have stripped away some of the mystery surrounding the powerhouse that drives the Earth’s magnetic field. The research strongly suggests that several of the characteristics of the field that were long thought to operate independently of one another, such as the field’s polarity and strength, may be linked. If so, then the strength of the field, which has been waning for several thousand years, may herald a pole reversal-a time where compasses all over the Earth would point south instead of north. The findings are being published in today’s issue of Proceedings of the National Academy of Sciences.



John Tarduno, professor of geophysics, took 14 students on four excursions, the most recent in the summer of 2000, far above the Arctic Circle to pitch tents near 95-million-year-old rocks on the snow-covered islands of Ellesmere and Axel Heiberg. The rocks, part of a formation called the Strand Fiord, were spewed forth from ancient volcanoes during a time when the Earth’s magnetic field was particularly stable. As the volcanoes’ lava cooled to become igneous rock, tiny crystals lined up with the Earth’s magnetic field and were solidified in the rock. Tarduno was seeking these crystals and the data they preserved about the magnetic field.

Tarduno wanted to find whether the crystals in this region bore evidence of brief fluctuations in the magnetic field. Several more accessible areas of the globe house such crystals, but Tarduno had to go to the edge of the "tangent cylinder"-a giant, theoretical cylinder that runs through the Earth like a pimento through an olive. This cylinder extends away from the Earth’s solid iron core to the north and south poles and represents an area of possible high turbulence in the molten iron of the core, stirred up by the Earth’s spin. Near the edge of this cylinder of turbulence scientists believe the liquid iron should be the most chaotic, twisting up the magnetic lines of force. Where this edge contacts the Earth’s crust high above the Arctic Circle should lie traces of the twisted magnetic field in the crystals.


But not just any place along this edge would do. Tarduno needed to find rocks around 95 million years old because they were formed in the middle of an ancient time of highly unusual magnetic stability. That time of stability, called a superchron, lasted for tens of millions of years-a rarity when magnetic reversals can happen in as little as a few tens of thousands of years. Tarduno wanted to know how stable or chaotic the magnetic field was during that time along the supposedly turbulent edge of the tangent cylinder. If the field was chaotic during the stable superchron, then there would probably be no correlation between north-south pole reversals and the way molten iron in the core generated that field. On the other hand, if the field near the cylinder’s edge was stable throughout the superchron, then it becomes more likely that turbulence in the liquid outer core was related to making the Earth’s poles reverse. The answer would peel away another layer of mystery about how the Earth generates its magnetic field.

Above the Arctic Circle, just 11 degrees south of the North Pole, Tarduno and his students pitched tents near the volcanic strata of the Strand Fiord Formation to find and retrieve layers from the 95-million-year-old superchron on the edge of the tangent cylinder. Before they could drill into the rock to retrieve samples, however, they had to precisely note which way the North Pole lay so that they could tell if the crystals in their samples showed any sign of a full or partial pole reversal. Compasses were useless because at their latitude they were actually farther north than the epicenter of the magnetic north pole, and though that could have been corrected for, at such high latitudes solar winds can create unpredictable variations in the field. The network of satellites that makes up the Global Positioning System were likewise useless because much of the drilling had to be done in deep, narrow valleys where the satellites’ signals couldn’t penetrate. The team had to use a sun compass, a way to gauge direction using knowledge of where the sun is at a specific time of day. Once they had determined which way the true North Pole lay, Tarduno and his students drilled out several sections of the 95-million-year-old rock, labeled it, and packed it up to be shipped back to the University of Rochester.

Once back at the University, Tarduno used a SQUID magnetometer, a device that can detect extremely minute amounts of magnetism in small samples, to determine the direction and intensity of the magnetic signature sealed in the crystals in the rock. What they found was that there was little deviation in the direction or intensity in the field, even though the molten iron beneath was theoretically very turbulent. This suggests that the fluctuations in the iron of the inner core of the Earth were not contorting the magnetic field but were efficiently creating a stable and intense field.

This study shows a correlation between the stability of the poles and the intensity of the field, meaning there’s likely a single mechanism in the Earth governing the magnetic field. The news comes as a bit of a relief for scientists who would otherwise have to uncover multiple interacting mechanisms to create a working model.

The findings also suggest that humanity is in for a surprise in the not-too-distant future. Since the Earth’s magnetic field has been decreasing in intensity for the last several thousand years, and the intensity and likelihood of pole reversals are linked, in as little as a few centuries we may see the Earth’s magnetic poles flip, sending everyone’s compasses angling toward the South Pole.

Tarduno plans to extend these studies into the very ancient Earth in the hopes of discovering how the Earth came to have a magnetic field at all.

The research was funded by the National Science Foundation and the Canadian Polar Shelf Project.

Jonathan Sherwood | EurekAlert!

More articles from Earth Sciences:

nachricht Shrinking of Greenland's glaciers began accelerating in 2000, research finds
12.12.2019 | Ohio State University

nachricht One-third of recent global methane increase comes from tropical Africa
11.12.2019 | European Geosciences Union

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Virus multiplication in 3D

Vaccinia viruses serve as a vaccine against human smallpox and as the basis of new cancer therapies. Two studies now provide fascinating insights into their unusual propagation strategy at the atomic level.

For viruses to multiply, they usually need the support of the cells they infect. In many cases, only in their host’s nucleus can they find the machines,...

Im Focus: Cheers! Maxwell's electromagnetism extended to smaller scales

More than one hundred and fifty years have passed since the publication of James Clerk Maxwell's "A Dynamical Theory of the Electromagnetic Field" (1865). What would our lives be without this publication?

It is difficult to imagine, as this treatise revolutionized our fundamental understanding of electric fields, magnetic fields, and light. The twenty original...

Im Focus: Highly charged ion paves the way towards new physics

In a joint experimental and theoretical work performed at the Heidelberg Max Planck Institute for Nuclear Physics, an international team of physicists detected for the first time an orbital crossing in the highly charged ion Pr⁹⁺. Optical spectra were recorded employing an electron beam ion trap and analysed with the aid of atomic structure calculations. A proposed nHz-wide transition has been identified and its energy was determined with high precision. Theory predicts a very high sensitivity to new physics and extremely low susceptibility to external perturbations for this “clock line” making it a unique candidate for proposed precision studies.

Laser spectroscopy of neutral atoms and singly charged ions has reached astonishing precision by merit of a chain of technological advances during the past...

Im Focus: Ultrafast stimulated emission microscopy of single nanocrystals in Science

The ability to investigate the dynamics of single particle at the nano-scale and femtosecond level remained an unfathomed dream for years. It was not until the dawn of the 21st century that nanotechnology and femtoscience gradually merged together and the first ultrafast microscopy of individual quantum dots (QDs) and molecules was accomplished.

Ultrafast microscopy studies entirely rely on detecting nanoparticles or single molecules with luminescence techniques, which require efficient emitters to...

Im Focus: How to induce magnetism in graphene

Graphene, a two-dimensional structure made of carbon, is a material with excellent mechanical, electronic and optical properties. However, it did not seem suitable for magnetic applications. Together with international partners, Empa researchers have now succeeded in synthesizing a unique nanographene predicted in the 1970s, which conclusively demonstrates that carbon in very specific forms has magnetic properties that could permit future spintronic applications. The results have just been published in the renowned journal Nature Nanotechnology.

Depending on the shape and orientation of their edges, graphene nanostructures (also known as nanographenes) can have very different properties – for example,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

The Future of Work

03.12.2019 | Event News

First International Conference on Agrophotovoltaics in August 2020

15.11.2019 | Event News

Laser Symposium on Electromobility in Aachen: trends for the mobility revolution

15.11.2019 | Event News

 
Latest News

Supporting structures of wind turbines contribute to wind farm blockage effect

13.12.2019 | Physics and Astronomy

Chinese team makes nanoscopy breakthrough

13.12.2019 | Physics and Astronomy

Tiny quantum sensors watch materials transform under pressure

13.12.2019 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>