The two mysterious continent-sized chunks inside the Earth that intrigue scientists

Magma

Magma

In a strange corner of our solar system, there are two amorphous extraterrestrial masses.

They are the size of continents, and are thought to spend their time waiting for food to fall on them, which they then simply absorb.

Its natural habitat is even more atypical than its diet.

You could call it “rocky”: all around, exotic minerals of unknown shades and shapes.

It’s otherwise fairly barren, save for a shimmering sea in the distance, so vast it holds as much water as all of Earth’s oceans combined.

Every day, the “time” is the same: a few 1,827°Cand its pressure in some areas is about 1.3 million times that of the Earth’s surface.

In this overwhelming environment, atoms warp and even the most familiar materials begin to behave eccentrically: rock is flexible like plastic, while oxygen behaves like metal.

But this scorching hot spot is not on an alien planet, and these masses are not strictly wild animals.

He is, in fact, on Earth, only deep within it.

In this strange world

The environment in question is the lower mantle, the layer of rock that sits just above the planet’s core.

This mostly solid mantle is another world, a swirling place dotted with a kaleidoscope of crystals, from diamonds (of which there are about a quadrillion tons) to minerals so rare they don’t exist on the planet’s surface. .

minerals

Many of the most abundant materials found deep within the earth have rarely been seen on the surface.

In fact, the most abundant rocks in this layer, bridgmanite and davemaoite, are largely a mystery to scientists.

They need the clean ultra-high pressures inside the planet to grow and they crumble if introduced into our realm.

We can only see them in their natural form when they are trapped inside diamonds that reach the surface. And even then, it’s impossible to know what they actually look like inside the Earth, because their physical properties are so different at the pressures under which they normally exist.

For its part, that the distant “ocean” does not contain a drop of liquid.

It is made from water trapped in the mineral olivine, which makes up over 50% of the upper mantle. At deeper levels it transforms into indigo blue ringwoodite crystals.

“At these depths, the chemistry totally changes,” explains Vedran Lekić, associate professor of geology at the University of Maryland (USA).

“As far as we know, some minerals become more transparent,” he says.

But it is these amorphous masses that most intrigue geologists around the world.

a complicated problem

In 1970, the Soviet Union embarked on one of the most ambitious exploration projects in human history: it attempted to drill as deep as possible into the earth’s crust.

This solid layer of rock, sitting above the Earth’s mostly solid mantle and possibly partially molten core, is the only part of the planet that has never been seen by the human eye.

Nobody knew what would happen if they tried to go through it.

In August 1994, the Kola super-deep well, located in the middle of an inhospitable expanse of arctic tundra in northeastern Russia, had reached incredible depthsextending some 12,260 meters underground.

At first, the team leading the project made predictions about what they expected to find, in particular that the Earth would warm by one degree for every 100 meters traveled towards its center.

However, it soon became apparent that this was not the case: in the mid-1980s, when they reached 10 km, the temperature was already 180°C, almost double what was expected.

But then the drill jammed.

The well (closed welded), August 2012

Nobody has ever succeeded in venturing beyond the earth’s crust: the well-knit super-deep Kola.

Under these extreme conditions, the granite was no longer drillable: it behaved more like plastic than like rock.

The experiment was stopped and no one has managed to cross the threshold of the crust to date.

We know much less about the Earth’s mantle than we know about outer space. -which we can observe with telescopes-, because everything we know is very, very indirect”, explains Bernhard Steinberger, researcher in geodynamics at the University of Oslo (Norway).

So how do you study an environment that cannot be seen or accessed, where even the chemical properties of the most common materials are distorted beyond recognition?

It turns out there is another way.

inverted coconut

Seismology involves the study of energy waves produced by the sudden movement of the ground during massive events such as earthquakes.

Among them are the so-called “surface waves”, which are superficial, and the “internal waves”, which pass through the interior of the Earth.

To capture them, scientists use instruments the opposite of the earthquakes they detect and examine anything that has made its way.

By analyzing the different wave patterns, they can begin to piece together what might be happening hundreds of miles underground.

It was these characteristics that enabled the Danish geophysicist Inge Lehmann to make an important discovery in 1936.

Seven years earlier, a major earthquake in New Zealand had led to a surprising seismic result: a type of internal wave, which can pass through any material, had managed to pass through the Earth, but it had been “bent” by an obstacle on the way.

And, another type of wave, which cannot pass through liquids, could not pass.

This overturned the long held belief that the core was completely solid and led to the modern theory that there is a solid interior wrapped in a liquid outer shell, a sort of inverted bogeyman, if you will.

A mystery hidden deep inside me

Screenshot from LLSVP video published in 2016 article

Screenshot from LLSVP video published in the 2016 paper “Morphology of Seismically Slow Lower Mantle Structures” by Sanne Cottaar and Vedran Lekić.

Over time, the method has been refined, making it possible to visualize the hidden depths of the Earth in three dimensions, “using the same techniques as computed tomography” used in medicine, says Lekić.

Almost immediately, this led to the discovery of Earth’s two amorphous masses.

Called “Large Low Shear Velocity Provinces” (LLSVPS), these are two colossal regions, where seismic waves meet resistance and slow down.

One of them, called “Tuzo” is located under Africa; the other“Jason”, is under the pacific ocean.

As with the Earth’s core, these areas are markedly different from the rest of the mantle and are some of the largest structures on the planet.

Their structures are thousands of kilometers wide and occupy 6% of the volume of the entire planet.

Estimates of its heights vary, but Tuzo is thought to be up to 800 km high, which is equivalent to around 90 Everests stacked on top of each other.

Jason could stretch for 1,800 km, which corresponds to about 203 Everests.

Their misshapen bodies cling to the Earth’s core, like two amoebas to a speck of dust.

“There is 100% certainty that these two regions are, on average, slower [en términos de la rapidez con que las ondas sísmicas se mueven a través de ellas] than the surrounding region. It’s not up for debate,” says Lekić.

“The problem is that our ability to see in that region is blurry.”

Besides how titanic their forms are, almost everything else about them still uncertainincluding how they formed, what they are made of and how they could affect our planet.

Scientists know something is going on there and they are trying to figure out exactly what, believing that understanding them would help unravel some of the most enduring mysteries in geology, such as the formation of the Earth, the planet’s ultimate fate “ghost” Theia and the inexplicable presence of volcanoes in some parts of the world.

They could even shed light on how the Earth is likely to change over the next few millennia.

* If you want to know the different theories considered about Tuzo and Jason, Click hereand read the original note on BBC Travel (in English)

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