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The Hulking Blobs Beneath Us: Continents of the Underworld Come Into Focus

Over the years, better maps kept showing the same bloblike features. One huddles under Africa; the other is beneath the Pacific.

They lurk where the planet’s molten iron core meets its rocky mantle, floating like mega-continents in the underworld. Their highest points may measure over 100 times the height of Everest. And if you somehow brought them to the surface, God forbid, they contain enough material to cover the entire globe in a lava lake roughly 100 kilometers deep.

“It would be like having an object in the sky, and asking, ‘Is that the moon?’ And people are like, no. ‘Is that the sun?’ No. ‘What is it?’ We don’t know!” said Vedran Lekić, a seismologist at the University of Maryland. “And whatever it is, it is intimately tied to the evolution of the Earth.”

The first mystery of these hulking, hidden seismic features is whether they’re made of different stuff than the rest of the Earth’s mantle. The second: How do these patterns in the deep leave traces on our surface world?

Neither case is settled. But in recent years, many earth scientists have begun to make the case that these vague shapes are piles of dense, smoldering rock that date to the dawn of the planet. And multiple studies in the past year have argued that their persistent influence might be responsible for long-puzzling patterns in volcanic hot spots like Hawaii.

“These are the largest things on the planet,” said Ed Garnero, a seismologist at Arizona State University. “Only recently have I started thinking, ‘Wow, this is potentially super profound.’”

Core of the Matter
If an omnipotent scientific illustrator halved the Earth, they would first need to cut through the thin crust we live on, which is broken into shifting tectonic plates. Then they’d pass through the rocky mantle. Only at 2,900 kilometers down, about halfway to the very center, would they hit the core-mantle boundary.

To map that part of the Earth, seismologists use the waves released by earthquakes. As the waves rattle outward, they change speed depending on what material they pass through. That causes them to arrive at different monitoring stations at different times. In 1984, the Harvard researcher Adam Dziewonski first integrated data from many different earthquakes into a global map. The two blobs showed up immediately, attached to the core on either side like Princess Leia side buns.

In these regions, earthquake waves seem to slow down, suggesting that the blobs are hotter than the surrounding mantle. How do we know this? Rock expands when heated. That causes waves to travel sluggishly through warm regions, said Garnero, like the slower vibrations moving through a loose guitar string.

The slowing waves gave these features their formal name: large low-shear-velocity provinces, or LLSVPs — an unmagical abbreviation that may have contributed to the topic’s low profile. “We are also to blame,” said Sanne Cottaar, a seismologist at the University of Cambridge, “for misnaming this feature so badly.”

 

RTWT @ Continents of the Underworld Come Into Focus | Quanta Magazine

{ 11 comments… add one }
  • Jack January 15, 2020, 1:20 PM

    Well, there you have it: Global warming.

  • jwm January 15, 2020, 3:10 PM

    As if we didn’t have enough to worry about. :/

    JWM

  • Terry January 15, 2020, 4:53 PM

    Looks like there may be two chambers of Hell. Under Africa makes sense. Under the Pacific is curious.

  • Auntie Analogue January 15, 2020, 4:56 PM

    Hulking Blobs?

    Sounds like a job for Lou Ferrigno and Steve McQueen!

  • Anonymous January 16, 2020, 7:26 AM

    Counterweights that allow a relatively wobble-free spin with the differences in land & water mass involved.
    Off the top of my head theory.

  • John the River January 16, 2020, 7:53 AM

    Read elsewhere that 4.5 billion years ago a Mars sized object called Theia collided with Gaia — the ancient Earth; the remains of that object is buried deep within the Earth like a rifle bullet in a tree.
    Without that collision present day Earth wouldn’t have the mass and the orbit it currently does, within the “Goldilocks Zone”.

  • ghostsniper January 16, 2020, 11:23 AM

    “Caldera”
    ———–
    Another ghostsniper classic

    =========

    Yellowstone Park sits directly over a hot spot. The volcano is quiet today, only the geysers and hot springs remind us that there is an enormous volcano under the beautiful scenery. Just 600,000 years ago a huge eruption filled the area with lava flows. After the enormous eruption there was a void under the top of the volcano. The weight of the volcano caused the top to come crashing down forming the large Caldera in the park. Since the hot spot remains active, another giant eruption will almost certainly occur. The question is, when?

    A new cycle of volcanic activity has begun. The number and strength of earthquakes have increased; new hot springs have appeared and existing ones have grown. A large area to the northeast of Yellowstone Lake has uplifted. Will it erupt again? If so, when? How much damage will it cause?

    Not until the thermal imaging units were installed in satellites in the nineties was the scientific community aware that calderas existed. They were simply too large to be seen with the naked eye or any known instruments before that time. It was then that the vast size of the Yellowstone caldera became apparent. On the order of 600 miles by 400 miles scientists were stunned to realize the magnitude of the forces it contained.

    Imagine one of those Betty Crocker dinners. You pour a packet of vegetables into the Pyrex then you dump a can of gravy on it. Then you spoon dollops of gooey dough on top of that, then into the oven at three-fifty for an hour. When its done you have a crispy roof over a boiling vat of gruel. If you poke a hole through the roof the gruel will ooze up from below. This is a Caldera.

    The earth is seven-tenths water so it is in keeping that most of the worlds Caldera’s are underwater. The largest known Caldera is located approximately four thousand miles west of California in the center of the Pacific ocean and it is called Panthea. Less than one hundred feet below the surface of the sea bottom the temperature of Panthea is estimated at over eight thousand degrees. Steam regulary is emitted from hundreds of surface orifices over Panthea and the surface is constantly moving.

    Panthea is estimated to be over two hundred and fifty miles in depth and nine hundred miles in diameter, the largest of all Calderas. Tied to the San Andreas fault on the United States western seaboard Panthea is considered the origin for most of the seismic activity in this region as well as in Alaska and eastern Asia including Japan, China.

    Recent readings of Panthea’s core temperatures indicate that changes are occuring as the surrounding waters escalate in temperature. Biologists are plotting computer models to try to determine what the ripple effect will be if the caldera roof would collapse due to liquification. The first sign would be Richter machines going off the scale, on the order of fifteen point oh. This alone would disturb the very mantle of the earth itself. Second, the collapse in volume of the earths surface, the ceiling of the caldera, would cause huge tension release within the oceans body. Think of a large plate of spaghetti with suddenly no plate. When the structure of the ocean floor itself is removed, it is not clear what exactly will happen in other parts of the world.

    Suddenly the oceans water would sweep into the new void created by the caldera. This water must come from somewhere, it would come from everywhere simultaneously. Like pouring cold coffee down the kitchen sink. Gone. The level of the seas would drop six feet in a matter of minutes and coastlines would be scrubbed as massive volumes of seawater were pulled toward the void. Millions of people worldwide would be swept along with the rushing seas. Entire cities would vanish, coastlines too would no longer exist.

    Pantheon is roughly the size of the Gulf of Mexico, but two hundred and fifty miles deep. This space would consume large amounts of both the Pacific and Atlantic oceans. In hours the level of the worlds oceans would drop more than 100 feet. Icebergs in the Arctic sea would topple as they touched the sea bed, the Mediterranean sea would be dry. Hydrostatic vacuum would cause all buildings on all coasts to collapse.

    As trillions of gallons of seawater drain into the gaping boiling Panthea the water will be instantly heated to eight thousand degrees creating a gaseous explosive mixture of thousands of chemicals simultaneously. The blowback from this will shower the stratosphere worldwide.

    Matt Rense is a thirty four year old construction superintendent who lives in the town of Crystal Bay outside Chesapeake, Virginia with his wife Sarah and their two kids Jarrod and Sensia, ages 10 and 8. Sarah is a teacher in a private school named Colloquial First where their kids attend. Matt has a past time as an Ultralight pilot and this may be the key to evacuating his family to safe ground further inland from the coast of their home as pandemonium reigns all around them.

  • james wilson January 16, 2020, 12:10 PM

    Ghost, the Younger Dryas is our most recent catastrophe, circa 14,500 years back to 11,600 back. In Greenland temperatures rose 18 degrees F in a few months. The great large mammal extinctions in North and South America occurred then, leaving Africa untouched. Whatever was facing the sun at that moment was torched. Temperatures dropped again, then rose again and staid in this Goldilocks zone nearly 12 thousand years which the nitwits are complaining about. It cannot be impressed upon people that they are sitting on the thin crust over an uncertain rock protected by an even thinner crust of atmosphere, traveling though deep space. LGBTQ can be impressed upon them, but not this.

  • Uncle Mikey January 16, 2020, 4:25 PM

    Ghost, that’s a pretty weird version of “Happy, and Peppy, and Bursting with Love” but I like it

  • ghostsniper January 16, 2020, 6:28 PM

    This wobbly ball is about 8000 miles in diameter. Ever been 8000 miles from where you are right now? I have not. But I have been 6000 miles. From here to Germany. From the surface to the center of the earth is about 4000 miles – longer than the US is wide.

    The tallest mountain is Mt Everest at about 6 miles high. The deepest point in the ocean is Challenger Deep at about 7 miles. Together, defining the maximum earth surface thickness, is about 13 miles. Contrast 13 with with the 4000. The known surface is but a tiny fraction of the whole. There’s a whole lot of sumfink going on way down below and most of it is unknown.

    Yeah, they got their imaginations, and their simulations, and their core samples, and their satelites, but they don’t actaully “know” wtf is going on down there. Suffice to say, whatever is down there owns all of us and everything on the planet and if it ever decides to change it’s game plan, well, we will change ours too whether we like it or not. We’re riders, not drivers, as it were.

    When I hear these arrogant, ignorant experts go on and on about how the very thin smear of human influence on very limited parts of the earths surface are destroying the whole thing I have to just laff and laff and laff. What I really want to do is backhand their silly ass to and fro so fast it would like they are watching a japanese ping pong game.

  • ghostsniper January 16, 2020, 6:30 PM

    I erred, it’s about 4000 miles from here to germany.

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