highest peaks on earth?

[Laika]

Valich,

You claimed that:

Again, using tectonic terminology, the mantle is all rock compositional layers above the outer core:

But your selected quotes do not support it. They were:

"The mantle is a dense, hot layer of semi-solid rock."

"Mantle rock consists of olivines, different pyroxenes and other mafic minerals."

"Magma is molten rock beneath the surface of the earth."

"Magma is naturally occurring molten or paritally molten rock material, generated within the Earth."

Magma is molten rock containing liquids, crystals, and dissolved gases that forms within the upper part of the Earth's mantle and crust. When erupted onto the Earth's surface, it is called lava."

Please explain how these quotes support your assertion that tectonic geologists group all layers above the core into a single compositional unit. I have some experience in tectonics and I have certainly not found this to be the case. In fact, differences in rock composition are fundamental to the subject.

 

[valich]

First, I hope that you are asking me this for the sake of learning and not for the sake of argument, as that is not what Sciforum is about.

By definition, the mantle starts at the outer core and ends at the crust: lower and upper mantle. But to complicate matters, when I studied a geology degree some ten or fifteen years ago, the textbooks didn't even talk about a lithospere and asthenosphere. Back then we learned that the crust extended down some 20-150 km and ended at the Moho discontinuity. Now that definition has changed. Today, geologists recognize that the asthenosphere is a magma area that infuences the plates above in the lithosphere. Today, they say that the Earth's crust is less than 10 km in oceans and less than 30 km on continents (depending on the elevated mountainous anomalies).

I've read recent articles that have stated that there are pockets of molten magma at the boundary between the outer core and the lower mantle. If this is true, then it would be unreasonable to assume that some magma is not interchanged in these boundary areas. Also there is the theory that hot spots are attributed to straight plumes arising from the outer core to the lithosphere, but the definition of hot spots in geology today is very ambiguous. For instance, most geologists consider Yellowstone to be a hot spot, but recent evidence points to no direct plume underneath. Instead, an underlying chamber of magma - probably due to convection currents in the mantle.

I live and learn and learn as I write. Do you disagree with any of the above?

 

[Ophiolite]

Yes. I disagree with several of the explicit and implicit statements made. However, you aren't worth bothering with any further on this thread. Your dishonest posting style has been recognised by all visitors here. My work is done for the moment.

 

[valich]

In Geology 101 we learn that there is an inner core, outer core, mantle and crust. Using tectonic terminology we now divide the upper part of the mantle into a mostly magma astenosphere with overlying plates in the lithosphere that itiself consists of the upper most part of the mantle and a small crust between 0-100 km thick. If you went through all 8 pages of these posts to compile a nice dictionary for me then you must've all come across the diagram that I posted, posted again below. I think the information below should help you completely understand the composition of the Earth and leave no further question? Magma is derived mostly - almost entirely - within the mantle. Many parts of the Earth's surface has no crust (see diagrams below), however, where their is crust it is made of either igneous (magma derived rock), metamorphic, or loose sedimentary material. When magma erupts from magma chambers, some of this material is bound to melt alongside the magma and be incorporated in it as it rises.

"Magma is molten rock often located inside a magma chamber beneath the surface of the Earth. Magma is a complex high-temperature silicate solution that is ancestral to all igneous rocks. It is capable of intrusion into adjacent crustal rocks or extrusion onto the surface. Magma exists between 650 and 1200 °C. Magma is under high pressure and sometimes emerges through volcanic vents in the form of flowing lava (molten rock as it exists above the Earth's surface) and pyroclastic ejecta. These products of a volcanic eruption usually contain liquids, crystals and dissolved gases which have never before reached the planet's surface. Magma collects in many separate magma chambers within the Earth's crust, and will have slightly different compositions in different places, which can occur at either a subduction zone, a rift zone or mid-oceanic ridge, or above a mantle plume hotspot. Magma's formation only takes place under specific conditions in the Earth's asthenosphere." http://en.wikipedia.org/wiki/Magma

"In certain regions, upwelling hot magma can break through the crust and reach the surface. In the oceans, magma reaches the surface at the boundaries between plates called spreading centers, like the Mid-Atlantic Ridge, and there new oceanic crust forms." http://www.pbs.org/wnet/savageearth/hellscrust/

"The mantle is about 2,900 kilometers (1,800 miles) thick and is composed of hot, melted rock, called magma, that flows in slow-moving [convection] currents. The magma of the mantle is made up of different minerals than those in the solid rock of the crust." http://education.nacse.org/Curriculum/earth_insideearth.html

"Definition of Magma: Geology. The molten rock material under the earth's crust, from which igneous rock is formed by cooling."
http://www.answers.com/magma&r=67

http://pubs.usgs.gov/publications/text/inside.html

"The next layer is the mantle, which is composed mainly of ferro-magnesium silicates. It is about 2900 km thick, and is separated into the upper and lower mantle. This is where most of the internal heat of the Earth is located. Large convective cells in the mantle circulate heat and drive plate tectonic processes." http://scign.jpl.nasa.gov/learn/plate1.htm

 

[valich]

Geologists do not use the term magma to apply to the fluid outer core because magma is liquid rock and rock is an aggregate of minerals. Since the Earth's outer core consists primarly two elements (80% liquid iron and the rest mostly nickel with some trace elements), it is not considered as molten rock because it is not much of an aggregate. Although I have heard some non-scientific sources call the liquid outer core magma: technically this is an improper use of the term.

Ophiolite is a good example of a hard uplifted rock that can easily be turned in molten magma. However Ophiolite is usually found deep underwater in ocean plates and turns to magma basalts in subduction zones, where the plates go down (subduct), because of its huge mafic content (~55% silica).

"The core is probably composed mostly of iron (or nickel/iron) though some lighter elements may be present, too. Temperatures at the center of the core may be as high as 7500 K, hotter than the surface of the Sun. The lower mantle is probably mostly silicon, magnesium and oxygen with some iron, calcium and aluminum. The upper mantle is mostly olivene and pyroxene (iron/magnesium silicates), calcium and aluminum. We know most of this only from seismic techniques;samples of upper mantle arrive at the surface as lava from volcanoes" http://www.nineplanets.org/earth.html

"Outer Core

30.8% of Earth's mass;
depth of 2,890-5,150 kilometers (1,806 - 3,219 miles)
The outer core is a hot, electrically conducting liquid within which convective motion occurs. This conductive layer combines with Earth's rotation to create a dynamo effect that maintains a system of electrical currents known as the Earth's magnetic field. It is also responsible for the subtle jerking of Earth's rotation. This layer is not as dense as pure molten iron, which indicates the presence of lighter elements. Scientists suspect that about 10% of the layer is composed of sulfur and/or oxygen because these elements are abundant in the cosmos and dissolve readily in molten iron." http://www.earthsci.org/geopro/platec2/platec2.html

A list of rocks can be found at: http://www.reference.com/browse/wiki/List_of_rocks or http://en.wikipedia.org/wiki/List_of_rocks
w/ pictures at: http://www.geocities.com/EnchantedForest/Cottage/3292/rocks.htm

The layer located directly under the mantle. The outer core is composed of liquid nickel and iron. Scientists believe that the outer core is liquid because S waves from an earthquake bounce of the layer instead of passing through it.
volcano.und.edu/vwdocs/vwlessons/lessons/Ch1CMA/Vocab1_teacher.html

One of the layers of the Earth. The outer core is about 1400 miles thick and is made of melted metals. The Outer Core is much hotter then the mantle.
www.beavton.k12.or.us/greenway/leahy/00-01/rocks/rockglossary.htm

The layer of the earth made of nickel and iron in the liquid state
wwwf.countryday.net/FacStf/ms/schniebec/Glossary%20.htm

The section of the core, between 2,900-5,150 km deep, consists of liquid iron alloy.
www.wwnorton.com/college/geo/earth2/glossary/o.htm

The following diagram further depicts the Earth's layer's with the state of their constituitional components (solid, liquid, magma):

Inner core: depth of 5,150-6,370 kilometres
The inner core is made of solid iron and nickel and is unattached to the mantle, suspended in the molten outer core. It is believed to have solidified as a result of pressure-freezing which occurs to most liquids under extreme pressure.

Outer core: depth of 2,890-5,150 kilometres
The outer core is a hot, electrically conducting liquid (mainly Iron and Nickel). This conductive layer combines with Earth's rotation to create a dynamo effect that maintains a system of electrical currents creating the Earth's magnetic field. It is also responsible for the subtle jerking of Earth's rotation. This layer is not as dense as pure molten iron, which indicates the presence of lighter elements. Scientists suspect that about 10% of the layer is composed of sulphur and oxygen because these elements are abundant in the cosmos and dissolve readily in molten iron.

D" layer: depth of 2,700-2,890 kilometres
This layer is 200 to 300 kilometres thick. Although it is often identified as part of the lower mantle, seismic evidence suggests the D" layer might differ chemically from the lower mantle lying above it. Scientists think that the material either dissolved in the core, or was able to sink through the mantle but not into the core because of its density.

Lower mantle: depth of 650-2,890 kilometres
The lower mantle is probably composed mainly of silicon, magnesium, and oxygen. It probably also contains some iron, calcium, and aluminium. Scientists make these deductions by assuming the Earth has a similar abundance and proportion of cosmic elements as found in the Sun and primitive meteorites.

Transition region: depth of 400-650 kilometres
The transition region or mesosphere (for middle mantle), sometimes called the fertile layer and is the source of basaltic magmas. It also contains calcium, aluminium, and garnet, which is a complex aluminium-bearing silicate mineral. This layer is dense when cold because of the garnet. It is buoyant when hot because these minerals melt easily to form basalt which can then rise through the upper layers as magma.

Upper mantle: depth of 10-400 kilometres
Solid fragments of the upper mantle have been found in eroded mountain belts and volcanic eruptions. Olivine (Mg,Fe)2SiO4 and pyroxene (Mg,Fe)SiO3 have been found. These and other minerals are crystalline at high temperatures. Part of the upper mantle called the asthenosphere might be partially molten.

Oceanic crust: depth of 0-10 kilometres
The majority of the Earth's crust was made through volcanic activity. The oceanic ridge system, a 40,000 kilometre network of volcanoes, generates new oceanic crust at the rate of 17 km3 per year, covering the ocean floor with an igneous rock called basalt. Hawaii and Iceland are two examples of the accumulation of basalt islands.

Continental crust: depth of 0-75 kilometres
This is the outer part of the Earth composed essentially of crystalline rocks. These are low-density buoyant minerals dominated mostly by quartz (SiO2) and feldspars (metal-poor silicates). The crust is the surface of the Earth. Because cold rocks deform slowly, we refer to this rigid outer shell as the lithosphere (the rocky or strong layer).

http://www.moorlandschool.co.uk/earth/earths_structure.htm

Hypoithetical Interaction between the Outer Core and the Mantle:

"Upward-sliding "avalanches" at the core-mantle boundary probably occur frequently on many scales, but all would tend to warm the mantle and cool the liquid core. (The inner core is toward the top of this image.) Truly massive CMB avalanches could disrupt the geodynamo and cause Earth's dipole field to collapse; if the mantle got hot enough, a magma plume might form that could reach all the way to Earth's surface." http://www.lbl.gov/Science-Articles/Archive/Phys-earth-core.html

"As we go deeper into the Earth the temperature increases along a curve we call the "geotherm" or the "geothermal gradient":
1. in deep mines (up to 2 kms) and deep drill holes (up to 10 kms) we see an increase in temperature of 2 to 3 degrees per 100 meters;
2. the mantle is below its solidus (minimum melting temperature) almost every where and at almost all depths;
3. the outer core is liquid so the lower mantle/outer core boundary is ~3700o C.;
4. the inner core is solid so the outer core / inner core boundary is ~4300o C.

http://www.geol.binghamton.edu/faculty/naslund/Geol.111.lect20d.html

 

[Laika]

Valich,

I have issues with some of what you've posted.

Using tectonic terminology we now divide the upper part of the mantle into a mostly magma astenosphere

The asthenosphere is a ductile solid, not a liquid. Even at spreading centres the melting is only partial.

Many parts of the Earth's surface has no crust (see diagrams below)

Even with the aid of your diagram I don't really see where you're coming from with this. What do you suppose constitutes the Earth's surface in areas where the crust is absent?

"The mantle is about 2,900 kilometers (1,800 miles) thick and is composed of hot, melted rock, called magma, that flows in slow-moving [convection] currents. The magma of the mantle is made up of different minerals than those in the solid rock of the crust." http://education.nacse.org/Curricul...nsideearth.html

I know that this is not an original statement by you, but it perpetuates a misconception about the mantle. The mantle is solid rock. It is not molten.

Ophiolite is a good example of a hard uplifted rock that can easily be turned in molten magma. However Ophiolite is usually found deep underwater in ocean plates and turns to magma basalts in subduction zones, where the plates go down (subduct), because of its huge mafic content (~55% silica).

An ophiolite is never "found deep underwater in ocean plates". By definition, an ophiolite is a fragment of ocean lithosphere that has been emplaced on a continent by obduction. Also, what do you mean when you say that ophiolites can "easily be turned into molten magma"?

 

[doodah]

Valich-
Just for the fun of it: Let's assume that the crust can be differentiated from the mantle (which it is not part of, even if it is part of the lithosphere). Let's also assume that the mantle is composed of mafic, silicate material (low Si, high Fe, Mg).

The next layer is the mantle, which is composed mainly of ferro-magnesium silicates.

If these assumptions are true, and all magma comes from the mantle

Magma is derived mostly - almost entirely - within the mantle

then where does rhyolite/granite come from?

 

[valich]

Even with the aid of your diagram I don't really see where you're coming from with this. What do you suppose constitutes the Earth's surface in areas where the crust is absent?

There are areas on the Earth's surface where tectonic plates are exposed. The best example, although technically not on the "surface," although I'm sure you understand what I mean, is where mid-ocean ridges divide, and the resulting magma tectonic activity produces new crust.

"The asthenosphere is a ductile solid, not a liquid. Even at spreading centres the melting is only partial."

This is questionable and under debate. Some say the asthenosphere - and the entire mantle! - is a "plastic solid," while others say that it is magma and that this is how it causes the plates to move above it. I do not know. But the subject is still an open question.

It is a fact that ophiolites are found more on the ocean floor than they are on continents because of their higher mafic density. Ocean floors sink because they are more dense (heavier) while continental surfaces rise because they have a lower mafic content (silica density).

 

[Ophiolite]

What do you suppose constitutes the Earth's surface in areas where the crust is absent?

There are areas on the Earth's surface where tectonic plates are exposed.

You are saying tectonic plates are not, in part, crust!!!

"The asthenosphere is a ductile solid, not a liquid. Even at spreading centres the melting is only partial."

This is questionable and under debate. Some say the asthenosphere - and the entire mantle! - is a "plastic solid," while others say that it is magma and that this is how it causes the plates to move above it. I do not know. But the subject is still an open question.

So you will have no problem providing references to thos who believe that the entire mantle is magma. I am really looking forward to that.

It is a fact that ophiolites are found more on the ocean floor than they are on continents because of their higher mafic density. Ocean floors sink because they are more dense (heavier) while continental surfaces rise because they have a lower mafic content (silica density).

Get a grip sonny. Ocean floors begin life by rising. That's why we have a mid-ocean ridge, not a mid-ocean valley. [And don't try posting links about the central graben found on many of the MORs. That wont fly.] They then sink, as they cool and densify. Understand?
As Laika has clearly pointed out, while ophiolites originate from the oceanic crust and upper mantle, they are not so named until they have accreted during orogenisis onto a piece of continental crust. Understand?

 

[valich]

I repeat what another forum user replied to Ophiolite:

"Are you just creating a diversion as usual. And appealing to your so called greater formal education. Same old Ophiolite. Insults and intimidation are no substitute for substance."

Ophiolite: a sequence of rock characterized by "ultra"mafic rocks at the base and (in ascending order) gabbro, sheeted dikes, pillow lavas, and deep-sea sediments. The typical sequence of rocks constituting the oceanic crust." http://72.14.203.104/search?q=cache...glossary.pdf+oceanic+rhyolite+volcanoes&hl=en

And I add that "IT" should stay there!

 

[doodah]

"Ophiolites are sections of the oceanic crust and the subjacent upper mantle that have been uplifted or emplaced to be exposed within continental crustal rocks."
http://en.wikipedia.org/wiki/Ophiolite
While it's true that ophiolite sequences are created in ocean basins, the sequences are not called ophiolites until they have been accreted to and exposed in continental rocks.

 

[Laika]

Valich,

If you won't respond to Ophiolite, I hope you will to me.

I claimed that the asthenosphere is a ductile solid, and that even at spreading centres the melting is only partial.
You said:

This is questionable and under debate. Some say the asthenosphere - and the entire mantle! - is a "plastic solid," while others say that it is magma and that this is how it causes the plates to move above it. I do not know. But the subject is still an open question.

If you can give an example of a scientifically credible proponent of the idea that the mantle (or at least the asthenosphere) is molten I will be very surprised. To the best of my knowledge the subject is not an open question because seismic evidence has closed it quite effectively. I'm sure you know that liquids cannot transmit shear waves. This is why seismic studies show there to be a shear wave 'shadow' cast by the outer core. As you yourself have correctly pointed out, the outer core is concluded to be molten. The asthenosphere undeniably does transmit shear waves, although there is a slight decrease in their velocity. This indicates that the asthenosphere is a solid containing small quantities of melt. The wave velocity then generally rises steadily with depth through the mantle. At points where the increase is pronounced, transition to closer atomic packing is inferred.

 

[Ophiolite]

"Are you just creating a diversion as usual.

No. The diversions from fact are being generated, repeatedly, by you. I am merely correcting their tiresome inanity.

And appealing to your so called greater formal education.

1. If you've got it, flaunt it.
2. I have repeatedly used valid and relevant references to support my expression of contentions that are held by science. You, in contrast, have repeatedly used irrelevant facts to support contentions that are not grounded in science, are not supported by the scientific community, and derive from your failure to comprehend what you are reading.

Insults and intimidation are no substitute for substance."

You feel intimidated by me, do you? How telling.

 

[protostar]

The solid outer mantle is becoming more liquid.
when the solid outer mantle becomes mostly liquid,
the mantle will slip under the crust around the fixed axis of the central gyroscope core.
******
Core temp rises' the outer mantle loses its adhesive like quality
to plates sliding enmasse.
Our planets poles and its orbit are determined by its electromagnetic charge,
distribution of electromagnetic energy changes from moment to moment
Planets can change orbits when their charge of energy changes sufficiently.
( Just wanted to throw this in there.)

Now, which layer is producing the "out gassing" in tx and ok, oh, ny, pa, nj
and countless others?

 

[doodah]

The solid outer mantle is becoming more liquid.

are you talking about the asthenosphere? This is a hypothesis that I'm not aware of- you must have some sources?

when the solid outer mantle becomes mostly liquid,
the mantle will slip under the crust around the fixed axis of the central gyroscope core.

what is the "central gyroscope core"? Where us the mantle going to slip to? The equator?

Core temp rises' the outer mantle loses its adhesive like quality
to plates sliding enmasse.

Why would an increase in the temperature of the core cause the outer mantle to start plates sliding? It takes at least tens of thousands of years for heat from the core to affect the outer mantle, whether through convection or conduction.

Our planets poles and its orbit are determined by its electromagnetic charge,
distribution of electromagnetic energy changes from moment to moment
Planets can change orbits when their charge of energy changes sufficiently.
( Just wanted to throw this in there.)

the earth's electomagnetic field certainly determines the position of the magnetic poles, but are you suggesting that a change in this field could change our orbit?

Now, which layer is producing the "out gassing" in tx and ok, oh, ny, pa, nj
and countless others?

What outgassing are you referring to? What is the composition of the gas?

 

[protostar]

The raising internal temperature of the planet is slowly liquefying the semi-molten layers of magma nearest the outer mantle of the Earth, and lessoning the adhesive qualities of same, allowing the outer mantle, and the tectonic plates above, to swim on the molten layers below. The centrifugal force of the Earth's rotation acting on an imbalance already existent in the rotation of the planet = Chandler Wobble, will propel the movement of the outer mantle around the fixed position of the central core.
(Aesthenosphere/Lithosphere area)

PLANETOPHYSICAL STATE OF

THE EARTH AND LIFE

By DR. ALEXEY N. DMITRIEV*



Published in Russian, IICA Transactions, Volume 4, 1997



*Professor of Geology and Mineralogy, and Chief Scientific Member,

United Institute of Geology, Geophysics, and Mineralogy,

Siberian Department of Russian Academy of Sciences.

Expert on Global Ecology, and Fast -Processing Earth Events.



Russian to English Translation and Editing:

by A. N. Dmitriev, Andrew Tetenov, and Earl L. Crockett



Summary Paragraph

Current PlanetoPhysical alterations of the Earth are becoming irreversible. Strong evidence exists that these transformations are being caused by highly charged material and energetic non-uniformity's in anisotropic interstellar space which have broken into the interplanetary area of our Solar System. This "donation" of energy is producing hybrid processes and excited energy states in all planets, as well as the Sun. Effects here on Earth are to be found in the acceleration of the magnetic pole shift, in the vertical and horizontal ozone content distribution, and in the increased frequency and magnitude of significant catastrophic climatic events. There is growing probability that we are moving into a rapid temperature instability period similar to the one that took place 10,000 years ago. The adaptive responses of the biosphere, and humanity, to these new conditions may lead to a total global revision of the range of species and life on Earth. It is only through a deep understanding of the fundamental changes taking place in the natural environment surrounding us that politicians, and citizens a like, will be able to achieve balance with the renewing flow of PlanetoPhysical states and processes.

INTRODUCTION
Current, in process, geological, geophysical, and climatical alterations of the Earth are becoming more, and more, irreversible. At the present time researchers are revealing some of the causes which are leading to a general reorganization of the electro-magnetosphere (the electromagnetic skeleton) of our planet, and of its climatic machinery. A greater number of specialists in climatology, geophysics, planetophysics, and heliophysics are tending towards a cosmic causative sequence version for what is happening. Indeed, events of the last decade give strong evidence of unusually significant heliospheric and planetophysic transformations [1,2]. Given the quality, quantity, and scale of these transformations we may say that:

The climatic and biosphere processes here on Earth (through a tightly connected feedback system) are directly impacted by, and linked back to, the general overall transformational processes taking place in our Solar System. We must begin to organize our attention and thinking to understand that climatic changes on Earth are only one part, or link, in a whole chain of events taking place in our Heliosphere.

These deep physical processes, these new qualities of our physical and geological environment, will impose special adaptive challenges and requirements for all life forms on Earth. Considering the problems of adaptation our biosphere will have with these new physical conditions on Earth, we need to distinguish the general tendency and nature of the changes. As we will show below,these tendencies may be traced in the direction of planet energy capacity growth (capacitance), which is leading to a highly excited or charged state of some of Earth's systems.The most intense transformations are taking place in the planetary gas-plasma envelopes to which the productive possibilities of our biosphere are timed. Currently this new scenario of excess energy run-off is being formed, and observed:

In the ionosphere by plasma generation.

In the magnetosphere by magnetic storms.

In the atmosphere by cyclones.

This high-energy atmospheric phenomena, which was rare in the past, is now becoming more frequent, intense, and changed in its nature. The material composition of the gas-plasma envelope is also being transformed.

It is quite natural for the whole biota of the Earth to be subjected to these changing conditions of the electromagnetic field, and to the significant deep alterations of Earth's climatic machinery. These fundamental processes of change create a demand within all of Earth's life organisms for new forms of adaptation. The natural development of these new forms may lead to a total global revision of the range of species, and life, on Earth . New deeper qualities of life itself may come forth, bringing the new physical state of the Earth to an equilibrium with the new organismic possibilities of development, reproduction, and perfection. In this sense it is evident that we are faced with a problem of the adaptation of humanity to this new state of the Earth; new conditions on Earth whose biospheric qualities are varying, and non-uniformly distributed. Therefore the current period of transformation is transient, and the transition of life's representatives to the future may take place only after a deep evaluation of what it will take to comply with these new Earthly biospheric conditions. Each living representative on Earth will be getting a thorough "examination," or "quality control inspection," to determine it's ability to comply with these new conditions.These evolutionary challenges always require effort, or endurance, be it individual organisms, species, or communities. Therefore, it is not only the climate that is becoming new, but we as human beings are experiencing a global change in the vital processes of living organisms, or life itself; which is yet another link in the total process. We cannot treat such things separately, or individually.

 

[protostar]

Because the Earth’s core rotates about a slightly different axis than the mantle (due to the tug of the Sun and Moon), the core’s magnetic field is dragged through the mantle, passing unhindered because the mantle does not conduct electricity. The porous, iron-containing sediment stuck to the mantle, however, would resist the rotation of the magnetic field, creating just enough tug to perturb the Earth’s rotation.

‘As the core rotates it sweeps the magnetic field with it, which easily slips through the mantle with no resistance,’ said Buffett. ‘But if the bottom of the mantle has conductivity, then it’s not so easy to slip the magnetic field lines through the mantle. The magnetic field tends to stretch and shear or pull out right across the interface. That generates currents, and those currents damp out the motion and create the kind of dissipation we need to explain this lag in response.’
Outgassing?