[HN Gopher] Earth's innermost layer is a 644 kilometer wide ball...
___________________________________________________________________
Earth's innermost layer is a 644 kilometer wide ball of iron, new
study finds
Author : taubek
Score : 134 points
Date : 2023-02-22 06:38 UTC (2 days ago)
(HTM) web link (www.archyde.com)
(TXT) w3m dump (www.archyde.com)
| nerdponx wrote:
| Wait, I definitely remember reading about this in science
| magazines years ago: the earth's core is more like solid than
| liquid because it's under tremendous pressure from gravity, and
| it's spinning, and it's iron, which is why Earth has a magnetic
| field.
|
| Is the new discovery that there is actually a _fifth_ layer,
| which is solid, and that what we previously thought of as the
| "core" is actually liquid and not the innermost layer?
| pfdietz wrote:
| No, the Earth's magnetic field isn't because of iron being
| ferromagnetic, nor does it come from the solid inner core. The
| iron in the core is well above the Curie temperature at which
| ferromagnetism ceases.
|
| Rather, the Earth's magnetic field is due to currents flowing
| in the liquid outer core. Convection in the core drives the
| conductive metal across these currents, increasing them by a
| dynamo effect. This process occurs on a rather small scale and
| is difficult to model, and is also somewhat chaotic, leading to
| very occasional collapses and flips of the Earth's magnetic
| field.
| warent wrote:
| A _flip_ in the magnetic field? Has something like that ever
| happened in history or is ever predicted to happen? What
| would the damage be?
| GuB-42 wrote:
| We are talking about thousands of years for the flip to
| happen, and hundreds of thousands of years between each
| flip. We have geological records that it happened, as for
| the damage, there was a theory that it was linked to mass
| extinction, but latest research find it unlikely.
|
| It would still be bad for us, but not something worth
| worrying about right now.
| pfdietz wrote:
| It happens on a geological timescale, and is used to help
| date rocks. The ocean floor is marked with stripes of
| normal and reversed magnetic polarity (the magnetic field
| is faintly recorded in magnetization of minerals like
| magnetite), and this was a strong initial clue that led to
| the theory of seafloor spreading and plate tectonics.
|
| https://en.wikipedia.org/wiki/Geomagnetic_reversal
|
| https://www.usgs.gov/media/videos/pubtalk-72004-secrets-
| ston...
| xeromal wrote:
| You're in for a treat. Our magnetic field is currently
| doing some crazy stuff and moving quite fast.
|
| https://upload.wikimedia.org/wikipedia/commons/thumb/7/74/M
| a...
| nerdponx wrote:
| I would love to read the primary sources at the time
| describing peoples reactions to the movement of magnetic
| north. Were they surprised?
| throwawayx134ax wrote:
| Question: Do you mean current as in movement of material, or
| current as in movement of electric fields?
|
| Or is that not a valid distinction in this case?
| pfdietz wrote:
| Both meanings were used here. There are electrical
| currents, and there are flows of material through the
| magnetic field, producing voltages that sustain currents.
| The JxB forces also affect the flows. It's a highly
| nonlinear phenomenon (magnetohydronamics, or MHD).
| hydrogen7800 wrote:
| This reminds me of a paradox in my understanding of gravity. I
| often read about the pressure inside the earth resulting from
| the mass above, but the gravitational force inside a spherical
| shell is zero [0], and the only force acting at a given radius
| from the center is the mass of the sphere inside that radius.
|
| [0]http://hyperphysics.phy-
| astr.gsu.edu/hbase/Mechanics/sphshel...
| cossatot wrote:
| I believe the apparent paradox is that the 'net force' is not
| the same thing as pressure; it's basically the vector sum of
| pressure. Pressure in the Earth is an isotropic distribution
| of stresses, so that in a north-east-up coordinate system,
| the upward-pushing stress is matched by the downward-pushing
| stress, the eastward-pushing stress is matched by the
| westward-pushing stress, etc. So while these _sum_ to zero in
| some sense, their magnitude is the density of the rock
| between the point and the surface times the depth times
| gravity. This is like going deeper in the ocean-the forces
| are equal in all directions, meaning that they sum to zero in
| some sense and there is no directional flattening or
| translation, but they still increase with depth.
| codethief wrote:
| > I believe the apparent paradox is that the 'net force' is
| not the same thing as pressure
|
| I don't think that's what OP means. He's saying that the
| gravitational _force_ that acts on a given test particle
| that 's located inside Earth at a radius r=R from the
| center is determined only by the amount of mass "below it",
| i.e. the mass inside the ball of radius R, _not_ the matter
| making up the spherical shell R < r < R_E, where R_E is
| Earth's radius. Put differently, that (hollow) spherical
| shell does not cause any gravitational force on test
| particles inside it.
|
| This is absolutely correct and a consequence of Gauss's
| law, see
| https://en.wikipedia.org/wiki/Gauss%27s_law_for_gravity
|
| Meanwhile, you are talking about a different thing
| entirely: The pressure. The matter above (as well as below
| and next to) our test particle will obviously also
| experience gravity and get pulled down. So our test
| particle will experience an isotropic force from all sides,
| which is generally quantified as pressure (force per area).
| This pressure is obviously not zero (but no one ever
| claimed that) and does depend on the radius of the outer
| spherical shell above it, in the same way as the pressure
| under water depends on how deep you are.
| Salgat wrote:
| The net force is 0 in the same way that if two people are
| pushing you from opposite sides, their net force on you is
| also zero. You're still being crushed from both sides.
| [deleted]
| titzer wrote:
| Also note that that is only true for (being inside) a hollow
| shell, not for a solid sphere.
| zehaeva wrote:
| This is a confusion between the gravitational force that the
| core feels from the layers above, and the pressure that the
| layers above push down onto the core.
|
| That is, the core doesn't feel gravitational pull towards the
| outside, because it's balanced on that other side, but the
| outside is being pulling in towards the core, which pushes on
| the core.
|
| It might be easier to simplify the mental image by picturing
| just a slice of the whole thing.
| idlewords wrote:
| Think about sinking to the bottom of the Marianas Trench and
| then inflating a balloon just enough to make you neutrally
| buoyant. The net force on you will be zero, but you'd still
| be crushed by the pressure, which is the effect of many
| kilometers of seawater above you.
|
| Another way to think of this is to imagine a small sphere
| (like the size of a basketball) around the very center of the
| Earth. The matter in that sphere feels no net gravitational
| force, but it has to push back against the entire mass of the
| rest of the Earth, which is trying to fall into it.
| cossatot wrote:
| It's been known for decades that the Earth's core (which is
| mostly iron and nickel, as opposed to the mantle which is made
| of silicates) has a liquid outer layer and a solid inner layer.
| This is apparent because seismic shear waves can propagate
| through the inner layer but not the outer layer, which is
| diagnostic of the medium being liquid and not solid. (The shear
| or S-waves get _to_ the inner core because when a seismic
| pressure wave, which can travel through liquid, hits the inner-
| core-outer-core boundary, some of the energy is converted into
| shear waves. Jofer please correct me if this is inaccurate.)
|
| This article states that the inner core has two different
| concentric zones that have very different crystalline
| properties. In particular, the inner sanctum is anisotropic
| with respect to seismic wave propagation, and the outer sheath
| of the inner core is much more isotropic. This suggest that
| they have different geologic histories--the innermost core's
| crystallographic anisotropy may have resulted from an event
| early in Earth's history that deformed the crystals, much as
| mountain building events deform the crystals in Earth's crust
| and upper mantle. Then, the younger outer sheath of the inner
| core cooled and crystallized around the older inner bit later
| on, after the deforming event transpired.
| topher515 wrote:
| Can you explain a bit more about the difference between the
| anisotropic and isotopic nature of these different zones?
|
| Are both of these zones "solid" states of matter? Or does our
| intuition about states of matter not really work for
| materials at these exotic temperatures and pressures?
| Sharlin wrote:
| The article seems very poorly written. It reads like "We knew
| that Earth's inner core was a solid ball of iron... but now
| it's been discovered that the solid ball of iron actually has a
| solid ball of iron in its core!"
| selimnairb wrote:
| Yeah, I'm kind of scratching my head. This can't just be a
| distinction without a difference, can it? Maybe the discovery
| is that the solid core has two layers of different densities
| with a gradual "margin" between the two?
| throwaway81523 wrote:
| Site archyde.com seems to be some kind of weird splog. Is there a
| better source? What exactly is the new discovery, just that the
| innermost part of the core has a slightly different composition
| than the surrounding part?
| SllX wrote:
| Is it me, or does 644 kilometers wide seem kind of small for the
| inner core of the Earth? Does it even stay in place then, or does
| it kind of drift around slightly within the outer core over time?
| blacksmith_tb wrote:
| That seems like a point of reference thing to me, presumably
| the iron core is denser than the molten layer around it,
| gravity is pulling that towards it, but it's all spinning, and
| there are other gravitational influences from the moon, the
| rest of the solar system, etc. which could cause some slight
| sloshing around, I'd bet.
| treeman79 wrote:
| How big a ball of the rare but much heavier elements?
| autokad wrote:
| I've always wondered that. like wouldn't uranium, gold, and
| other heavier elements be more dominant the closer you get to
| the center of the core? but they are pretty confident on this
| iron thing
| wincy wrote:
| I've thought about this too, if dark matter is affected by
| gravity but not other forces, wouldn't that mean if we were
| able to drill to the center of any substantial gravity well
| (say the moon rather than the earth), would we be able to
| detect a big clump of dark matter? Does that mean there's a
| bunch of dark matter at the center of all the stars?
| pixl97 wrote:
| If we assume dark matter is a particle that only reacts via
| gravity, well, I'm not so sure you will.
|
| The question here is how your particle that only reacts via
| gravity loses energy. First it will have whatever momentum it
| has from the galaxy relative to the speed of our solar system
| and planet. Then as it falls into our gravity well it picks
| up even more speed. When it reaches the center of our planet
| it's hauling ass with no brakes so no reason to stop, so it
| goes screeching out the other side. Even if you somehow had a
| dark matter particle at 0 relative motion to your gravity
| well before it fell in, how long is it going to take to bleed
| off its gravitational energy?
| autokad wrote:
| I find the description of dark matter confusing. I hear
| statements like "dark matter has negligible interaction with
| ordinary matter". So, how do scientists know that dark matter
| exists?
|
| "The answer is that our galaxies spin too fast for the
| visible matter alone to hold them together. Dark matter,
| which makes up 27% of the universe, provides the additional
| gravitational force needed. In contrast, visible matter only
| makes up 5%."
|
| However, I'm left wondering whether dark matter does or
| doesn't interact significantly with visible matter.
| kerpotgh wrote:
| [dead]
| hoppla wrote:
| Earth's diameter is around 13000km, if there is an inner core
| with a 600 km width, you will find this core around 6000km below
| your feet, which is more than 1600 km below your feet (as the
| article correctly stated...)
| pmontra wrote:
| Yes, I also noticed it. It's too large a difference to be some
| miles to km conversion mistake. There is nothing 1600 km wide
| inside [1], not even the distance between the inner core and
| this new inner-inner core boundaries.
|
| [1] https://en.wikipedia.org/wiki/Core%E2%80%93mantle_boundary
| marginalia_nu wrote:
| I do think conversion is involved in generating these odd
| figures somehow. May not be the sole part, but the figure in
| the title is definitely an conversion that's sprouted
| additional sigfigs.
|
| 644 km is 400,000 miles (within 0.04% error).
| mkl wrote:
| Typo there: 400 miles. The actual paper's abstract [1] says
| "~650-km". In a skim through I didn't see anything that
| might correspond to the strange 1600km depth.
|
| [1] https://www.nature.com/articles/s41467-023-36074-2
| jmclnx wrote:
| And if I was asked, I would have guessed it would have been
| around 1000km.
| adamwong246 wrote:
| If only there were a decent way to mine the earth's core
| directly. There's more usable material already on Earth than the
| entire asteroid belt. It's just all melted together, molten and
| buried under thousands of miles of dirt.
| kelseyfrog wrote:
| Exactly! Plugging this into Wolfram Alpha reveals that Earth's
| core is worth $3.268x10^19 (US dollars)[1]. For comparison
| total global wealth is merely US$431T.
|
| 1. thirty-two quintillion six hundred eighty quadrillion
| dollars
| willis936 wrote:
| I bet it's worth more than that in usable electricity if we
| ran it through a heat exchanger + steam turbine.
| barelyauser wrote:
| These calculations are always bogus. Once mining starts, the
| price of iron will plummet. The exact same reason some
| reserves are seldom explored, as the decline in price will
| render the effort pointless.
| mkl wrote:
| In case you're serious, there isn't thousands of miles of dirt,
| but just metres to tens of metres. Then there's rock, which we
| do mine.
| vatys wrote:
| If we started mining the earth's core, it would seem infinite
| at first. Can we be trusted to only take a little bit and not
| eventually hollow it out?
| notfed wrote:
| If at some point we become anywhere advanced enough to do so,
| surely we could switch to mining other planets/objects.
| cossatot wrote:
| If we took the entire core to the surface (without collapsing
| the Earth which is impossible) we would cover the Earth with
| iron and nickel to a depth of hundreds of km.
| IncRnd wrote:
| This page is very rough and shouldn't be considered scientific. I
| didn't even find a link or the actual study name on the page. Not
| only that, Dr. Thanh-Son Pham is listed as a co-author but the
| page doesn't even mention the name of the second author, Hrvoje
| Tkalcic.
|
| I was able to find the home page for Dr. Thanh-Son Pham [1] and
| his google scholar page with his list of publications. [2] He
| looks extremely accomplished and a prolific researcher,
| especially for someone who appears to be so young. I was very
| impressed and can only think that others would have also liked to
| have a link to this paper. I found the actual paper online. [3]
| Abstract: Probing the Earth's center is critical for
| understanding planetary formation and evolution. However,
| geophysical inferences have been challenging due to the
| lack of seismological probes sensitive to the Earth's
| center. Here, by stacking waveforms recorded by a growing
| number of global seismic stations, we observe up-to-fivefold
| reverberating waves from selected earthquakes along the Earth's
| diameter. Differential travel times of these exotic arrival
| pairs, hitherto unreported in seismological literature,
| complement and improve currently available information. The
| inferred transversely isotropic inner-core model contains a
| ~650-km thick innermost ball with P-wave speeds ~4% slower
| at ~50deg from the Earth's rotation axis. In contrast, the
| inner core's outer shell displays much weaker anisotropy
| with the slowest direction in the equatorial plane. Our
| findings strengthen the evidence for an anisotropically-
| distinctive innermost inner core and its transition to a
| weakly anisotropic outer shell, which could be a fossilized
| record of a significant global event from the past.
|
| [1] https://sites.google.com/view/tsonpham/home
|
| [2] https://sites.google.com/view/tsonpham/publication
|
| [3] https://www.nature.com/articles/s41467-023-36074-2
| mikeyouse wrote:
| Yeah it looks like that website just stole the text from CNN
| and omitted a bunch of it. CNN didn't interview the other
| authors, but at least their figures are properly attributed
| (all tagged with Drew Whitehouse/Son Pham/Hrvoje Tkalcic --
| Whitehouse apparently works for National Computational
| Infrastructure and did the visualizations)and they directly
| link to the study.
|
| https://news.ycombinator.com/item?id=34929145
| photochemsyn wrote:
| Thanks for looking that up.
| zoklet-enjoyer wrote:
| NSFW link. I'm getting 2 large hentai ads. I hope they're not
| targeted haha
| trollerator23 wrote:
| Loool. They are targeted.
| mfer wrote:
| You don't have an ad blocker?
| zoklet-enjoyer wrote:
| Nope
| behringer wrote:
| The fbi recommends you get one
| adolph wrote:
| I think they did that to delegitimize ad blockers.
| 867-5309 wrote:
| the fbi still knows you like hentai. the ad blocker just,
| well.. blocks the hentai ad
| zoklet-enjoyer wrote:
| The weird thing is I don't like hentai
| notJim wrote:
| This is a safe space, we aren't shaming you here
| brianwawok wrote:
| At least if you are the kind of person who is a target of
| Hentai ads
| carabiner wrote:
| Ditto. I look at porn, but this is the first time I've seen a
| hentai ad attached to an innocuous article. The hentai ad is
| non-nude but says it's for adults.
| cjbgkagh wrote:
| I got science documentaries...
| umvi wrote:
| > I hope they're not targeted haha
|
| Most of my ads are targeted (tech-related based on stuff I've
| searched previously). I did not get any NSFW ads.
| kaapipo wrote:
| What's the shame in consuming content that would lead to
| hentai-themed targeted ads? :)
| kerpotgh wrote:
| [dead]
| Footkerchief wrote:
| Actual study link
| https://www.nature.com/articles/s41467-023-36074-2
| null3cksor wrote:
| I saw a documentary recently about this, its called 'Core' where
| they build a ship to dive into the mantle to spin up this ball of
| iron using nukes.
|
| On a serious note, it's amazing that we still have studies about
| this, and revising our knowledge!
| c256 wrote:
| NGL, I came here to get the link to make a _The Core_ joke to
| several friends...
| codethief wrote:
| Is that a common joke/meme? I only found https://www.reddit.c
| om/r/NetflixBestOf/comments/1p9vdb/the_c...
| potamic wrote:
| You mean, a movie?
| xeromal wrote:
| They're taking the piss
| MarcoZavala wrote:
| [dead]
| otikik wrote:
| Earth. What an irony.
| napolux wrote:
| i wanna touch it
| beeforpork wrote:
| Do you want to go there or do you want it to come to you?
| irrational wrote:
| I saw a documentary about people that did just that. It was
| called The Middle, or something like that.
| titaniumtown wrote:
| ...they touched the core of the earth?
| flatiron wrote:
| i thought you are going to say "the core"!
| kloch wrote:
| Are you sure? It's about the same temperature as the surface of
| the Sun.
|
| That means if you could see it, it would also be as white hot
| as the Sun seen from Space.
| magic_hamster wrote:
| Huh. I was under the impression this was known for a long time.
| If I recall, this is how the Earth's magnetic field is explained.
|
| Edit: I should really read more comment before adding my own,
| shouldn't I?
| dheera wrote:
| > latest research supports a theory that our blue planet holds an
| iron ball in the middle
|
| Uh, I thought my 6th grade teacher taught me this? What exactly
| is the "discovery"?
| Sharlin wrote:
| Yeah, it's a very poorly written article. The actual discovery
| seems to be that the solid inner core is divided into "outer"
| and "innermost" inner core, both of which solid iron-nickel but
| with somewhat different properties and a gradual transition
| between the layers.
| miga wrote:
| Would love to see "new study" that actually finds something new.
| LeifCarrotson wrote:
| This article shows the layers of the Earth as being perfectly
| spherical, like the oblate spheroid that is the top layer of
| Earth's crust. Little 8km high Everest mountain ranges or 8km
| deep Mariana trenches are peach fuzz on the 12,750 km diameter
| billiard ball, and I suppose it seems reasonable to assume that
| the mantle and core beneath are similarly shaped by gravity to
| near-perfect spheroids.
|
| But I recently learned about the African and Central Pacific
| mantle plumes, which rise far above the circles in those Pac-man
| renderings:
|
| https://www.theatlantic.com/science/archive/2020/01/seismic-...
|
| I expect that's old news to someone in the field, but I haven't
| thought critically about that diagram since high school.
| simonh wrote:
| I don't think it's really fair to say that. The difference in
| diameter across the axes is about a third of a percent. Given
| the size of the image, that's about 2 pixels. I think you're
| being a bit optimistic expecting to be able to perceive that
| with the naked eye.
| [deleted]
| anshumankmr wrote:
| This seems like a fantastic prompt for a sci fi novel.
| [deleted]
| itronitron wrote:
| I don't know why, but it took me a full minute to realize that
| graphic was spinning in a counter-clockwise fashion.
| dylan604 wrote:
| What would you expect for a planet where the sun rises in the
| east and sets in the west?
| bregma wrote:
| A plane, like the Earth, with the sun appearing and
| disappearing over the edge.
| dylan604 wrote:
| see, the flat earthers have it all wrong, which is
| evident by this comment. clearly, it is the sun that is
| traveling around the earth. i mean, if it disappeared, it
| wouldn't be coming back. so at least my theory is much
| more logical. and mars just likes to screw with us by
| reversing course a couple of times just to see if we're
| paying attention
| itronitron wrote:
| I think because the continents fade out as they approach
| the point closest to the viewer it makes it look like they
| are actually fading into the background and behind the red
| blobby thingies.
| alecbz wrote:
| Same -- I think something about the graphic (maybe how it
| blends in with the background in place?) creates that kind of
| "spinning balerina" illusion.
| jofer wrote:
| Mantle plumes don't significantly change the shape of the core
| or mantle, though. They're convection within the mantle. They
| rise from the core mantle boundary, but they're basically
| temperature features, not structural features.
|
| In other words, mantle plumes are parts of the mantle that are
| hotter than the other identically composed mantle around them.
|
| In contrast, the core and the crust are different compositions
| than the mantle.
|
| Just to clear up another common confusion, the mantle is very
| much solid, except for a tiny fraction of melt in a narrow and
| shallow zone called the athenosphere. The mantle flows over
| time despite being solid, though (think of a glacier). Just
| like a marble slab will bend over time (see benches in old
| graveyards that sag in the middle), the mantle slowly flows,
| but a hammer/etc would bounce right off of it. That's also true
| of large portions of the crust.
|
| As far as how smooth or not smooth the actually core boundaries
| are, we don't really know in detail. To a first order, they're
| smooth (i.e. we measure a broadly consistent radius from
| multiple directions), but that doesn't mean they're necessarily
| a "billard ball". There's likely fairly complex topography at
| the boundary that we can't easily measure.
| ASalazarMX wrote:
| > Just like a marble slab will bend over time (see benches in
| old graveyards that sag in the middle), the mantle slowly
| flows
|
| I had to see more of this, and it took me a while because
| most results are about construction and marble products. It
| looks like thin slabs of marble bow because of microfractures
| and internal stress, not by flowing.
|
| https://link.springer.com/article/10.1007/s00254-008-1307-z
| thehappypm wrote:
| Microfractures and internal stress are a form of flowing in
| this case.
| hcrisp wrote:
| Does the athenosphere produce surface lava?
| jofer wrote:
| That's a surprisingly complex question. The best answer is
| probably "sometimes".
|
| The chemistry of volcanic rocks gives a lot of clues as to
| the origin of the melt. The athenosphere is actually a bit
| poorly defined in this sense (it's a mechanical
| classification, not a chemical classification). Regardless,
| it's easy to distinguish magmas with a pure mantle source
| from others. MORB (mid ocean ridge basalt) is a common
| acronym for volcanic rocks with a chemistry that indicates
| they're essentially pure mantle melt.
|
| In the most common type of volcanoes you see on land (arc
| volcanoes), magma forms due to the introduction of water
| and other volatiles that lower the melting point of the
| upper mantle. That's what happens at arc volcanoes like the
| Cascades or Mt Fuji in Japan. It's not exactly coming from
| the athenosphere in that case, and it's often the
| lithospheric mantle and lower crust that are being melted.
| It's not heat that causes it, but instead the introduction
| of water.
|
| Volcanoes can also form due to the introduction of extra
| heat, as happens above hotspot volcanoes (e.g. the
| Galapagos or Hawaii). In many of those cases, you're
| basically seeing the athenosphere supplying extra heat to
| the mantle lithosphere and crust and melting it. The magma
| usually isn't coming directly from the athenosphere in
| those cases (though some of it can and does). However,
| flood basalts are an extreme case of hotspots, and their
| chemical signatures suggest that it's more or less melt
| directly from the athenosphere.
|
| Finally, one of the most common types of volcano on the
| planet does come directly from the athenosphere: mid ocean
| ridge systems. (Where the term MORB comes from) Those are
| almost entirely deep in the oceans, so non-geologists don't
| think about them as much, but they make up the bulk of
| volcanic activity on Earth. In those cases, you're
| essentially bringing the athenosphere up and melting more
| and more of it as it rises. Those are the cases where magma
| is most directly sourced from the athenosphere.
| bcbrown wrote:
| I'm curious how water would lower the melting point of
| solid rock. I'm aware that adding ethanol to water lowers
| the boiling point of the resulting solution, but that's a
| combination of two liquids. I can't think of a physical
| mechanism where adding a liquid to hot solid rock results
| in hot liquid rock.
|
| Where does the water come from? Is it liquid, or gaseous?
| jofer wrote:
| It's more or less the same way putting salt on ice causes
| it to melt. Diffusion still occurs with solids, just at a
| lower rate than with liquids.
|
| As for whether it's liquid or gaseous, I probably
| shouldn't have called it "water", and should have said
| "hydrogen and oxygen in silicate minerals". Silicates
| always have oxygen, but some hydrogen too (hydroxyl
| groups - i.e. OH).
|
| Basically, you have minerals that transform to other
| minerals at depth due to the pressures and temperatures
| involve. That transformation leads to the release of
| hydrogen and oxygen as they're in one crystal structure
| and not in the other. (Basically, minerals with hydroxyl
| groups transform into minerals that do not have hydrogen
| in their composition, releasing hydrogen and oxygen in
| the process.) That hydrogen and oxygen diffuses into
| adjacent mineral crystals and can cause them to melt.
|
| With that said, any time you have magma (i.e. melt), it's
| going to have H2O, CO2, halogens, etc dissolved in it,
| just like water has oxygen and carbon dioxide dissolved
| in it. We talk about these in simple terms of "H2O" and
| "CO2" etc, but often the details of how things are bonded
| are a bit different, just like CO2 dissolved in water
| isn't exactly CO2, but is carbonic acid (H2CO3) instead.
| bcbrown wrote:
| Fascinating stuff, thanks for the explanation.
| valarauko wrote:
| > In other words, mantle plumes are parts of the mantle that
| are hotter than the other identically composed mantle around
| them.
|
| The parent's link suggests that alternate views exist, that
| the mantle plumes are indeed chemically distinct from the
| surrounding rock.
|
| From the linked article: This suggests that
| the edges of the blobs mark a transition between materials,
| not just temperature. In this view, the blobs are
| so-called thermochemical piles, clumps of dense rock with a
| distinct chemical composition. Because of their prolonged
| contact with the core, they are hotter than the rest of the
| mantle, causing plumes to sprout.
| jofer wrote:
| Yes, there's a chemical component as well. I was
| simplifying. Regardless, though, they're not core material
| rising up. They're still basically olivine+pyroxenes+etc,
| same as what's around them. They're not the exact same, and
| indeed they bring deep mantle material up, but they're not
| nickle-iron rising up from the outer core, which is what I
| was trying to get across.
| hguant wrote:
| >They rise from the core mantle boundary, but they're
| basically temperature features, not structural features.
|
| my understanding was that this was not actually a settled
| topic, and there was ongoing debate as to whether or not they
| were thermochemical structures, with the main evidence
| against them being "basically temperature features" the fact
| that they're not a classic plume shape
| jofer wrote:
| Yeah, it's far from settled in detail, and for a long time
| there was a camp that maintained that mantle plumes did not
| really exist in the normal sense.
|
| However, further imaging work seems to show that 1) they
| actually do seem to be a classic plume shape in many cases
| (or, more precisely, have complex shapes compatible with
| convection), and 2) most do have temperature anomalies
| associated with them. Some things we thought were plume
| related may not be, but folks are much more in agreement
| that they look a lot more like convection-related features.
|
| E.g. compare these two papers (which are both basically
| review papers): https://www.sciencedirect.com/science/artic
| le/abs/pii/S00128...
| https://www.nature.com/articles/s43017-021-00168-6
| hutzlibu wrote:
| Layman question: why isn't the core of the earth made up of the
| most dense and heavy elements? One would assume, that they sink
| in to the deepest.
|
| But of course, there is also the spinning of the earth, that
| counters it and makes the heavier elements go outside?
| BurningFrog wrote:
| Yeah, I've heard that the heat from all the Uranium in the
| center is a big reason the core is still hot.
| hutzlibu wrote:
| Yes, that is kind of the question in my head: is the core of
| the earth basically a nuclear reactor? And if not, why not?
| mikeyouse wrote:
| It's a weird article/website -- they just stole most of the text
| from CNN. Including a section where they say, "Geoscientists
| first suggested that Earth's core might have an imperceptible
| extra layer about 20 years ago, according to a press release
| leaked to CNN News."
|
| There's no hint of who runs it/operates it -- is it some sort of
| auto-plagiarizer?
|
| The cribbed article is here:
| https://www.cnn.com/2023/02/21/world/earths-core-iron-metall...
| NetOpWibby wrote:
| Thank you
| xjwm wrote:
| Interesting that the core is oversized. 640Km should be enough
| for any body.
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