Oddly Behaving Blobs Beneath Earth’s Surface Finally Explained

Nov 28, 2017

By Dan Robitzski

The boundary between the Earth’s outermost layer, the crust, and the underlying mantle is speckled with mysterious, blob-like regions. Scientists have long known about these odd pockets, which are called ultralow-velocity zones. They slow down the seismic waves caused by earthquakes and may be the culprit for deep mantle plumes, which can lead to volcanic hotspots like those that created Yellowstone National Park or the Hawai’ian Islands.

Researchers have postulated a number of explanations for what these ultralow-velocity zones are made of and how they’re formed. But none of those ideas quite fit the data, especially given how differently some of the zones behave from one another.

Now, a team of scientists is proposing a new model that includes not only a feasible composition but also a plausible origin story for ultralow-velocity zones. Even so, the scientists behind the study concede that there could be different or even individual variations for other types of these mysterious, subterranean regions beyond their new findings.

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7 comments on “Oddly Behaving Blobs Beneath Earth’s Surface Finally Explained

  • What most interests me here is how this might impact the early earth perhaps even before plate tectonics was a thing and the mantle was too thin and too hot to have any compressive strength.

    This generation of weak spots and volcanic islands in extensive shallow unsalty seas may be the location for abiogenesis as hot black or cool white smokers may not have existed in time.

    This hydrogenated iron (II, III ?) peroxide may have a significance.



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  • “Assuming this process has been going on for all 4.5 billion years of Earth’s existence, the researchers say that all known ultralow-velocity zones could have been formed in this manner, even if just 100 billion pounds (45 billion kg) of water — one-10th of all the oceanic water on Earth — reacted with iron each year.”

    Yet another appallingly written science article whose author obviously didn’t understand what he trying to report on.

    What he was trying to say was that if 45 billion kg of seawater had reacted and combined with iron in the mantle for each of earth’s 4.5 billion years then to date a total of 2 x 10^20 kg of seawater would have been lost to the mantle in this way – about 1/10th of the seawater remaining on earth.

    Even that would still be wrong as the mass of seawater on earth is currently about 1.4 x 10^21 kg so the correct fraction would be 1/7th.

    [pedantic mode off]



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  • It just goes to show, Arkrid, that sub editors are no longer a thing in publishing. Fortunately a tenth of all the oceans every year is clearly not a sustainable process. Resequencing the sentence would fix it.

    ultralow-velocity zones could have been formed in this manner, using just one-10th of all the oceanic water on Earth, even if 100 billion pounds (45 billion kg) of water reacted with iron each year.

    This sort of mindless re-arrangement is what catches me out when under pressure to reduce word count. The inappropriate positioning of just suggests, hasty edits.



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  • phil rimmer #1
    Nov 28, 2017 at 1:47 pm

    What most interests me here is
    how this might impact the early earth
    perhaps even before plate tectonics was a thing
    and the mantle was too thin and too hot
    to have any compressive strength.

    ^^^^^^^^^^^^^^^^^^

    @OP – link :- This additional hydrogen makes the iron peroxide stable under extreme conditions
    and denser than surrounding minerals,
    giving rise to the distinct zones that behave differently than the rest of the mantle.

    I think there are some very significant features of this!

    First:- As we know that according to mapping by gravity satellites, the Earth is an oblate spheroid with gravity field anomalies.

    http://gisgeography.com/ellipsoid-oblate-spheroid-earth/

    Geoid (Image courtesy of NASA/JPL) (see link.)

    Vertical datums are lumpy and irregular. This is because of the varying densities in the Earth in different places. There are gravity anomalies such as mountainous areas have more mass.

    This means that mean sea level is not as smooth as everyone thinks it is. Geoids are not constant and they differ from place-to-place. Geoids have undulations as you move around on the Earth. The Earth is not as round as we like to pretend it is. We have lumps or undulations on them as they come back to us in the form of a geoid. The geoids put the lumps back into our nice smooth horizontal datum coordinate system.

    Second:- We know that the Moon was in a very low orbit with (guessing) approximately a five hour day, over the early Earth as the crust stabilised and seas formed.

    https://phys.org/news/2016-10-theory-moon.html

    In the new model, a high energy collision left a mass of vaporized and molten material from which the Earth and Moon formed. The Earth was set spinning with a two-hour day, its axis pointing towards the Sun.

    Because the collision could have been more energetic than in the current theory, the material from Earth and the impactor would have mixed together, and both Earth and Moon condensed from the same material and therefore have a similar composition.

    As angular momentum was dissipated through tidal forces, the Moon receded from the Earth until it reached a point called the “LaPlace plane transition,” where the forces from the Earth on the Moon became less important than gravitational forces from the Sun. This caused some of the angular momentum of the Earth-Moon system to transfer to the Earth-Sun system.

    This made no major difference to the Earth’s orbit around the Sun, but it did flip Earth upright. At this point, the models built by the team show the Moon orbiting Earth at a high angle, or inclination, to the equator.

    Over a few tens of million years, the Moon continued to slowly move away from Earth until it reached a second transition point, the Cassini transition, at which point the inclination of the Moon—the angle between the Moon’s orbit and the Earth’s orbit about the sun—dropped to about five degrees, putting the Moon more or less in its current orbit.

    The new theory elegantly explains the Moon’s orbit and composition based on a single, giant impact at the beginning, Stewart said. No extra intervening steps are required to nudge things along.

    This would have created massive tides in any seas, AND in the crust.

    Third:- As we know from measurements of the icy moons of Jupiter etc. variations in gravity due to an elliptical orbit can cause crustal tides, even in tidally locked synchronous moons!

    https://astronomynow.com/2016/04/15/europas-flexing-icy-crust-might-make-more-heat-than-scientists-thought/

    Jupiter’s moon Europa is under a constant gravitational assault. As it orbits, Europa’s icy surface heaves and falls with the pull of Jupiter’s gravity, creating enough heat, scientists think, to support a global ocean beneath the moon’s solid shell.

    If there were denser patches under the crust in early Earth, they would have a stronger gravitational attraction and more movement than the surrounding crust, with each pass under the low orbiting Moon.

    This would have a churning effect with the fluid rocks under the crust of Earth, which would interact with the Coriolis effect generated by the spin!



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  • Many thanks for this new Moon model, Alan. I hadn’t come across it.

    The astonishingly high tidal forces from the early moon orbit has always intrigued me over the pre-tectonic behaviours of the earth’s surface and as abiogenesis gets pushed back and back we have to remember to keep the primal conditions for life in sync.

    The repeated hyper-tidal-stretching of the cooling, thin, soft, crust will, at some critical point lead to tearing as the crust hardens, allowing water to descend and hydrogenate the iron (II, III?) peroxide. With its greater density and tendency to sink it will created the crustal hiatus that spawns volcanic islands.

    I suspect if this is the case, the use of seawater would have been much higher earlier, creating much thicker and stronger areas of crust from volcanic rock, which in turn would put all the tensile strain on increasingly reduced lengths of the original cooling crust, increasing the tearing effect, especially at the land edge.

    We might imagine that plates were formed in this way, with tears at the trailing edge of a volcanically thickened section. (The thicker, the higher, the cooler, the stronger.)

    I suspect that abiogenesis gets all its needed chemical feedstock in the region between volcanic upwelling due to tidal tears and a sustaining hiatus formation and the the run off from the newly uplifted land.

    In the early archean oceans DNA damage due to UV would have been 1000 times worse than now with destructive mutation rates in the photic zone. Life had to form in the sea below 30m if it was to survive. The chemistries of hydrothermal vents is convincing but not complete. However some of the missing chemistry for abiogenesis appears to need UV and little drying pools. The hyper UV may have worked particularly well on the pools at the edge of the new exposed volcanic land and the new-formed chemical run-off into the ocean and the nearby tears and up-wellings would have put the chemical mix together in the ideal location.



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  • phil rimmer #5
    Nov 29, 2017 at 12:59 pm

    The repeated hyper-tidal-stretching of the cooling, thin, soft, crust will, at some critical point lead to tearing as the crust hardens, allowing water to descend and hydrogenate the iron (II, III?) peroxide.

    As we were discussing on this other thread, we can’t assume that primordial seawater was of the same salinity as the present levels built up by rain draining salt via rivers into an evaporating sea, as at present.

    https://www.richarddawkins.net/2017/11/we-just-sent-a-message-to-try-to-talk-to-aliens-on-another-world/#li-comment-228140
    The charged particles in this ocean could respond to Jupiter’s magnetic field and produce an opposing force, limiting its effect on the aurora. While models of the moon suggest that the oceans can’t be that close to the surface, the new results indicate the ocean has to be less than 330 km deep. The thickness of the ocean isn’t clear; it could either be broad and not very salty or thinner with levels of dissolved minerals.

    The water on early earth, could have come from volcanism or later from comets!

    Seas could even have been temporary, evaporated, stripped off by the solar wind, and later replaced by water from comets!

    @#4 -The Earth was set spinning with a two-hour day,
    its axis pointing towards the Sun.

    If that was the case, that axis would have considerable implications for day and night temperatures and the states and distribution of of any surface water or other liquids!



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  • phil rimmer #5
    Nov 29, 2017 at 12:59 pm

    The repeated hyper-tidal-stretching of the cooling, thin, soft, crust will, at some critical point lead to tearing as the crust hardens, allowing water to descend and hydrogenate the iron (II, III?) peroxide.

    Talking of tidal forces on the Earth’s crust, there is both a Super-Moon and a full-Moon at present, with maximum Spring-Tides!

    [http://www.bbc.co.uk/news/uk-42211288](http://www.bbc.co.uk/news/uk-42211288](http://www.bbc.co.uk/news/uk-42211288)

    Skywatchers could catch a glimpse of a so-called “supermoon” – when the Moon appears larger and brighter in the sky.

    At 15:47 GMT the Moon will appear about 7% larger and 15% brighter, with moonrise about 45 minutes later.

    The phenomenon happens when the Moon reaches its closest point to Earth, known as a perigee Moon.

    The Moon circuits the Earth in an elliptical or oval orbit – a supermoon occurs when the perigee Moon is also a full Moon.

    Robert Massey, of the Royal Astronomical Society, said it will appear brightest at midnight – when at its highest point above the horizon.

    The Met Office’s UK forecast suggests there will be clear spells this afternoon, so the supermoon may be visible.

    Last year the Moon made its closest approach to Earth since 1948 – it won’t be that close again until 25 November 2034.

    Nasa has called this weekend’s sighting the first in a “supermoon trilogy” over the next two months, with others to come on 1 January and 31 January.

    This full Moon on Sunday afternoon – when it sits opposite the sun in the sky – will be 222,761 miles from Earth, closer than its average 238,900 miles.

    This Moon’s elliptical orbit means that its distance from Earth is not constant but varies across a full orbit.

    But within this uneven orbit there are further variations caused by the Earth’s movements around the Sun.

    These mean that the perigee – the closest approach – and full moon are not always in sync.

    But occasions when the perigee and full moon coincide have become known as supermoons.

    These high tidal forces still affect the flexing of the Earth’s crust, with various consequences.

    A mining engineer I talked to decades ago, told me that rock-falls – sometimes causing deep mine accidents, peaked at full-Moon!



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