22

Well, firstly it's important to recognise that the poles are merely the extremities of the shape of a magnetic field - the earth's magnetic field. All magnetic fields have polarities as such. However, you're asking why the field itself even exists, I gather. In this case it's generated by electric currents in the conductive molten iron (and other metals) ...


18

Actually, all of the three questions are directly related. As you noted, the Earth's magnetic field is generated by flow of molten conductive materials (probably mostly iron) in the outer core. (Contrary to popular belief, only the outer core and the oceans are liquid. The crust, mantle, and inner core are all solid. Solids can flow, but they have a shear ...


11

The entire process appears to take 3,000-4,000 years, according to Valet and Fournier's May 2016 review article "Deciphering records of geomagnetic reversals," which was published in AGU's Reviews of Geophysics. The complex dynamical structure of reversals is supported by sedimentary and volcanic records. Provided that resolution is adequate, the ...


7

You say you're "not given the declination angle", but you also say "the horizontal direction of magnetism of these lavas is due west". That's your declination angle, right there! Since I assume (from the very round-numbered location) that this is a homework exercise or similar, I won't work through the rest of the calculation here. However, if you need more ...


7

This is a big question: it essentially translates to ‘how do we do palaeomagnetism’? I will try to give a brief overview and links to more detailed explanations. I'm also going to focus on the ‘how’, and leave the ‘why’ to someone else (perhaps it would be best split out into a separate question?). To record the geomagnetic field, you need three things: A ...


6

The paleomagnetic field is recorded initially by minerals with a magnetic dipole, which is lined up with the surrounding magnetic field as long as the temperature is above the so called Curie Point. When these minerals cool down below this temperature the dipole is 'frozen' and fixed until the mineral is exposed again to a higher temperature. Different ...


4

First of all I will try to explain what a geomagnetic pole reversal is. A magnetic pole reversal happens when the magnetic field weakens until it can no longer sustain itself. This can take 1000-3000 Years or more to complete the time it takes is very variable. After years with a weak and sometimes variable magnetic field. The magnetic field re emerges in ...


4

As per our numerical calculations it takes about ~1000 years to completely flip the dynamo, that being said the current models are not even close to the actual parameters in the earth's core because it would take a humongous time to compute way beyond the capability of current computers. We published a paper back in 2014 where we talk about the role of ...


4

There is an alternative theory that the Earth's magnetic field is due to ocean currents since the sea contains (charged) dissolved salts. The flipping of the poles would then presumably be due to a major change in the currents. From what I have read there is a great deal of uncertainty about this subject. Physics world article


4

The surface of 'iron' meteorites certainly gets hot enough to exceed the curie temperature, hence the characteristic ablation texture that you see on meteorites in museums. However, that's a surface feature, and wouldn't affect the interior of all but the smallest of meteorites. The tumbling passage through the atmosphere for just a few seconds, coupled with ...


3

The Earth's initial accretion was about 4.5 billion years ago, and there is good Hf-W isotopic evidence that an iron core started to form within about 10 M years, and may have been largely complete within 30 M years. However, the Earth's dynamo, which is driven by isotopic heating and core rotation/convection, didn't switch on strait away. It must have built ...


3

It's common for dynamo models to predict a large reduction in the dipole field during a reversal. Proving it in the paleomagnetic record is another matter entirely. To characterize the geometry of the magnetic field, you need several simultaneous measurements, preferably with a good spatial distribution. Instead what you get are relatively infrequent, ...


2

Dr. Robert Strangeway kindly shared with me the poster he presented at AGU fall meeting 2017, the one I cited in the question based in the abstract only. I've included below some of the key parts of the poster with some text highlight added by me. He focus on Oxygen loss as a proxy of water loss. And the answer to my question that can be derived from this ...


2

The electromagnetic force and related field is a strong force at very small distances (governs the way the proton and electron are held to an atom) but is relatively weak over large distances. I don't see how that small force could act on processes involved in the convection of the mantle. If memory serves, the iron in magmas preserves the force of the ...


1

The simple answer is YES. The Earth's magnetic field is generated by a self-exciting dynamo in the fluid outer core. The interaction between electric currents and liquid motion sustain this field which is largely oriented along the rotation axis, since this rotation exerts constraints on the convection pattern. The dynamo field is largely dipolar but since ...


1

The forces of a magnetic field on materials that are not ferromagnetic and not electric conductors are negligible compared to pressure, tension, and buoyancy. It is likely safe to ignore them for the upper mantle. However, the lower mantle is a semiconductor with a significant thermal gradient, which induces electrical gradient via thermoelectricity. This ...


Only top voted, non community-wiki answers of a minimum length are eligible