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 In times of climate change: What a lake’s colour can tell about its condition
21.09.2017 | Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB)

nachricht Did marine sponges trigger the ‘Cambrian explosion’ through ‘ecosystem engineering’?
21.09.2017 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: LaserTAB: More efficient and precise contacts thanks to human-robot collaboration

At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.

Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Fraunhofer ISE Pushes World Record for Multicrystalline Silicon Solar Cells to 22.3 Percent

25.09.2017 | Power and Electrical Engineering

Usher syndrome: Gene therapy restores hearing and balance

25.09.2017 | Health and Medicine

An international team of physicists a coherent amplification effect in laser excited dielectrics

25.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>