Rare Chunks of Earth's Mantle Found Exposed In Maryland 53
Maya Wei-Haas writes via National Geographic: Standing among patches of muddy snow on the outskirts of Baltimore, Maryland, I bent down to pick up a piece of the planet that should have been hidden miles below my feet. On that chilly February day, I was out with a pair of geologists to see an exposed section of Earth's mantle. While this layer of rock is usually found between the planet's crust and core, a segment peeks out of the scrubby Maryland forest, offering scientists a rare chance to study Earth's innards up close. Even more intriguing, the rock's unusual chemical makeup suggests that this piece of mantle, along with chunks of lower crust scattered around Baltimore, was once part of the seafloor of a now-vanished ocean.
Over the roughly 490 million years since their formation, these hunks of Earth were smashed by shifting tectonic plates and broiled by searing hot fluids rushing through cracks, altering both their composition and sheen. Mantle rock is generally full of sparkly green crystals of the mineral olivine, but the rock in my hand was surprisingly unremarkable to look at: mottled yellow-brown stone occasionally flecked with black. Because of this geologic clobbering, scientists have struggled for more than a century to determine the precise origins of this series of rocks. Now, Guice and his colleagues have applied a fresh eye and state-of-the-art chemical analyses to the set of rocky exposures in Baltimore. Their work shows that the seemingly bland series of stones once lurked underneath the ancient Iapetus Ocean.
More than half a billion years ago, this ocean spanned some 3,000 to 5,000 miles, cutting through what is now the United States' eastern seaboard. Much of the land where the Appalachian mountains now stand was on one side of the ocean, and parts of the modern East Coast were on the other. "It's a huge ocean between them, and we've got a little bit of that ocean smooshed in Baltimore," says Guice, lead author of a recent study describing the find in the journal Geosphere.
Over the roughly 490 million years since their formation, these hunks of Earth were smashed by shifting tectonic plates and broiled by searing hot fluids rushing through cracks, altering both their composition and sheen. Mantle rock is generally full of sparkly green crystals of the mineral olivine, but the rock in my hand was surprisingly unremarkable to look at: mottled yellow-brown stone occasionally flecked with black. Because of this geologic clobbering, scientists have struggled for more than a century to determine the precise origins of this series of rocks. Now, Guice and his colleagues have applied a fresh eye and state-of-the-art chemical analyses to the set of rocky exposures in Baltimore. Their work shows that the seemingly bland series of stones once lurked underneath the ancient Iapetus Ocean.
More than half a billion years ago, this ocean spanned some 3,000 to 5,000 miles, cutting through what is now the United States' eastern seaboard. Much of the land where the Appalachian mountains now stand was on one side of the ocean, and parts of the modern East Coast were on the other. "It's a huge ocean between them, and we've got a little bit of that ocean smooshed in Baltimore," says Guice, lead author of a recent study describing the find in the journal Geosphere.
Style (Score:5, Insightful)
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Yeah, Nature and NOVA do the same thing, or fabricate a non-essential race against time. It really turns me off.
Smooshing ... (Score:2)
Re: Smooshing ... (Score:2)
Why, you understood what it meant, ... yes? ... Then it's a word.
(That ia literally the only thing that makes something a word or not.)
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Hm. By that criterion, "ia" is a word.
you misspelt ia (Score:3)
Hm. By that criterion, "ia" is a word.
Hm By that criterion, "ia" ia a word.
Fixed it four yoo.
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If that's all your looking for then that's all your're going to see.
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Racial diatribes about rocks in suburban Baltimore? Was there any mention of a rock's race?
The article did go on about the rock's color not meeting expectations. I assume that was a coded reference to race along with other message words like "lurking" and "clobbered".
There's also the use of "other side of the ocean". Who's that a reference to?
Re: Style (Score:3)
Seems to be so you can "connect" with the character, and it is a little "story".
You know, because they think we're a 55-year-old colonialist with an outrageous moustache and all the time in the world, in his club, sitting on a rocking chair and tartan with his pipe, to read a novel and go "Yees, yes, yes...*puffs pipe*".
And because they dream of being a writer.
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Apparently we can't understand science without a "human interest" story tacked on.
Apparently we also can't understand it without reading it twice. I don't know if it was just for me, but at the end of the article, there is a "READ THIS NEXT" that has the same photo and title as this article and links back to itself.
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At least it loads the actual content. Just use inspector to clean it up.
Right-click the modal and delete it from the DOM. Then remove all the CSS attributes from the body element (scroll lock implemented in JS).
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Because they write for normal humans, not impatient nerds like us.
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Open up with the summary of your thesis.
That is the reason I have given up reading on so many "social science" articles. They have anecdote after anecdote, and take their sweet time to come to their point. And usually their point would be moot.
Back when I learned how to write articles, we were told to start with the actual idea, and open it up, not the other way around.
To reiterate: anecdote != data, storytelling != science, and as always: correlation does not mean causation.
I have one question: (Score:2, Interesting)
How do they know it's mantle?
When the whole point is that they have nothing to compare it to.
At best, it's a hypothesis.
I'd like to see the chain of logic and experiments that back that assumption up.
As always: Not saying it's wrong. But that without that, it's anywhere between useless and harmful, even if it would be true. You know: The ternary logic of knowledge: Yes, no, dunno.
Re:I have one question: (Score:5, Funny)
They wouldn't be allowed to say it on the internet if it wasn't true.
Re:I have one question: (Score:5, Informative)
Layman geology enthusiast here. They know it's from the mantle primarily by the unique combination of the minerals and rocks that are present in the samples they dug up. By "unique" I mean they bear no resemblance to other surrounding rock. You're looking at rocks that are formed by one process, and then bang in the middle, a pocket of rock formed by an entirely different process.
The rocks being discussed here are "ophiolites" -- rocks composed of the same kind of minerals one finds in places like the mid-Atlantic ridge, not the weathered remains of the Appalachian mountains where they dug it up. But, there they are.
This article on Ophiolites is a good introduction for the casual reader: https://www.thoughtco.com/what... [thoughtco.com]
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Re: I have one question: (Score:2)
Uum, okay, but that leavesany other possibilities too.
Like, the simplest: How does a geologist ever get started then?
He looks at the ground beneath him and determines its composition. Then he walks somewhere else where the ground is different, and determines its composition. Following your argument, since it is different than what he knew before, it must have come from the mantle. But why?
Or is it a requirement that it is surrounded by the first type of ground? But why?
And if yes, then is there a size requi
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Are you sure you are a human and not just a pattern-matching machine?
This line of questioning is not the kind of thing a person would ask:
"Like, the simplest: How does a geologist ever get started then?
He looks at the ground beneath him and determines its composition. Then he walks somewhere else where the ground is different, and determines its composition. Following your argument, since it is different than what he knew before, it must have come from the mantle. But why?"
A human would not make such an obv
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Re:I have one question: (Score:5, Informative)
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There's about a dozen paragraphs that describe it in bits in a pieces, so it's worth reading the whole thing, but perhaps the 1 best part I could extract from the article is:
The key, Guice says, is in the chemistry of the mantle. The upper mantle is frequently melted a little bit at a time, but different minerals melt at different temperatures. So when the mantle partially melts, it becomes increasingly devoid of a predictable series of elements, which creates a specific chemical fingerprint.
Re: I have one question: (Score:2)
Ok, that's useful.
Now I of course still wonder if they checked how melted the mantle is. I mean drilled down to it and took a look.
But I'll take it.
And yes, ain't nobody got time to read a 12 page whatever just for that one bit. That's why I use Slashdot, after all! To
condense it to the gold nuggets. Because if I always had to read all that shit, this topic's spot on my "to read" list would be some few *centuries* before all the other stuff. (Like ALL of quantum physics, relativity, neurology, psychology,
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Haven't reached mantle in situ yet (Score:2, Informative)
Ok, that's useful.
Now I of course still wonder if they checked how melted the mantle is. I mean drilled down to it and took a look.
Nope.
There was a proposed attempt to drill down into the mantle and examine it in situ, Project Mohole [nasonline.org], but it was abandoned in the early '60s.
The deepest drilled hole to date was the Soviet Kola Superdeep Borehole [bbc.com], 12.2 km. That's deep... but not deep enough to reach the mantle.
--(posting as AC because I moderated... sorry!)
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Then go and read the frigging paper. Don't be some slashdotting "I know better than the experts do" naysayer at the drop of a hat. You read the title. Possibly you read the first paragraph. And now you're all pish-poshing it because you had a gut feeling that they must be wrong because they are experts, and experts are always wrong. You're strongly mplying that there is no evidence or logic or experiments at all without taking any effort to find this out first.
I swear, for a site for nerds, Slashdot has
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How do they know it's mantle?
When the whole point is that they have nothing to compare it to.
I guess they know the same way we know there are planets around other stars, by inference rather than direct observation. Not for a lack of trying. https://www.bbc.com/future/art... [bbc.com]
Rare? (Score:5, Interesting)
https://www.familyfuncanada.co... [familyfuncanada.com]
One of Canada's National Parks will let you dance on it or anything you like. The OP Article makes it sound like a unique discovery.
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I think this is "rare" in the sense that rare earth metals are "rare": i.e. orders of magnitude less common than granite and basalt.
Soldier's Delight (Score:4, Interesting)
One of the locations that they collected was Soldier's Delight Natural Environment Area.
https://dnr.maryland.gov/publi... [maryland.gov]
I have visited there and it is an interesting location. The vegetation struggle in the poor soil derived from the serpentine rocks.
There is an abandoned chromite pit mine where they collected one of their samples.
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Yes, Soldier's Delight is a neat hiking area. You can really see the exposed geology, and the very sparse scrubby conditions due to the lack of soil. I hiked there last fall. Well worth visiting if you are from the DC/NoVa/Maryland area.
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I don't know exactly why (Score:2)
But when I was reading this summary, something about the writing kept bringing my mind back to this:
https://youtu.be/aO0TUI9r-So [youtu.be]
The Infamous.. (Score:2)
...Maryland Mantle Flasher
km not mi (Score:1)