Researchers from Cologne University present important new constraints showing that plate tectonics started relatively slowly, although the early earth's interior was much hotter.
For this research, reported in the January 12, 2021 Proceedings of National Academy of Sciences, geologists and geophysicists led by Dr. Jonas Tusch investigated up to 3.5 billion year old igneous rocks from northwest Australia that cover 800 million years of earth's early history.
The analysis of these rock successions reveals that the oldest samples exhibit small anomalies in the isotope abundances of the element tungsten (W) that progressively diminish with time.
The origin of these anomalies, namely the relative abundance of 182W, relates to ancient heterogeneities in the terrestrial mantle that must have formed immediately after formation of the earth more than 4.5 billion years ago. The novel tool of high-precision 182W isotope measurements to rocks from the Pilbara Craton in Australia, that span an age range from 3.5 billion years to 2.7 billion years, was used in this study.
The preservation of these 182W anomalies in the igneous rocks from northwest Australia demonstrate that pristine mantle reservoirs from the beginning of our planet were conserved over timescales exceeding more than one billion years during the Hadean time period.
This finding is very surprising, because higher mantle temperatures in the early earth suggest that mantle convection was more extensive and much faster than today. Interestingly, the observed 182W anomalies start to diminish at around 3 billion years ago, within a geological era that is assumed to mark the beginning of modern plate tectonics.
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The onset of modern plate tectonics, involving subduction processes and mountain uplift, has been shown to be a key event triggering the emergence of large continental masses and an oxygen-rich atmosphere, all of which set the stage for the origin of more complex life. This artist conception of earth during the Hadean time period (which predates "modern" plate tectonics).
Here's to our oxygen-rich atmosphere of 2021. Breathe deep and sense those plates moving!
Steph [aka WW (Tungsten Tungsten;-))]
215,304 visits to PEOTS since October 2013. Here's to more posts in 2021!
ReplyDeleteThe headline was a bit misleading; I was hoping it meant that the plates are moving slower than previously thought. I know that's an inane hope, they have lots of sensors and are pretty confident about the rate of plate movement.
ReplyDeleteI can see the Hayward Fault from my house, it's just over a mile away as the seismic wave rolls. And the San Andreas Fault had a 3.6 early this morning, about 17 or 18 miles away. I'd be happy for the plates to slow their movements.
You're right. I changed it. See if this is better.
DeleteI wish all faults could be so readily fixed.
DeleteI have a project that's been on hold because the site is literally sitting on the Hayward Fault, and California codes won't allow you to build within 25' of an active fault's centerline. But it costs around $15,000 to dig a deep trench, drop the geotech engineer in there, and have them write a report of exactly where the fault line runs. Client has been unwilling to spend that, which is too bad as it's an amazing site for a house.
Wow. I don't think I would build so close to the Hayward Fault line, no matter how spectacular the site. What do architects/building codes consider the "centerline?"
DeleteThe process is to dig a trench, about 6-8' deep, roughly perpendicular to the known fault line. The geotech engineer looks for soil slippage lines within the last 12,000 years (I think that's the time frame). The slip lines define the centerline of the fault at that location.
DeleteWe can design to withstand the horizontal forces of an earthquake, but if the ground underneath different parts of the building decide to slide 16' horizontally, well, you're in a heap of trouble and building materials.
The distance to a fault line in general doesn't make that much difference, the lateral force doesn't change significantly in, say, 500'. As you doubtless know, the immediate soil type has a greater effect on motion. In the Loma Prieta earthquake 30 years ago the greatest damage was atop the loose squishy soil (often infill) of the Marina District and the Embarcadero (SF) and Cypress (Oakland) raised freeway structures. And they were >50 miles from the epicenter. USGS has worked with local jurisdictions to identify liquefaction zones, and we have to account for the additional forces in our designs.
I was in a high rise building in San Francisco adjacent to the Embarcadero, also built on infill mud, and it definitely moved a lot - toppled file cabinets, ceiling tiles down, broken water lines. And we were on the 4th floor, the folks from Arthur Anderson on the 44th floor looked none too happy walking down the stairs. My then clients at UCSF said they barely felt it, as that campus is built on a large outcrop of (asbestos-laden) serpentine rock. Similarly, my apartment (on the solid soil of Nob Hill 1 mile away) sustained no significant damage, even though it was not engineered nearly as well as my office.
Ah, memories.
Yes, of course the materials where buildings are built matters quite a bit. Glad you fared well in Loma Prieta.
DeleteAnd thanks for the scoop on centerline. Fault lines are squirrelly things.
And at a deeper layer the vagaries of the earth's crust and mantle can make a significant difference, just harder to see what's going on.
DeleteNow I wish I hadn't brought it up; Louise Kellogg was a close college friend starting from our undergraduate days - we lived in the same Coop House. Her specialty was modeling such things, and I helped by occasionally distracting her during her PhD research. She also used me as a sounding board, figuring if I could understand her work she could explain it to any idiot.
We'd lost touch over time, last saw her by pure chance on a San Francisco street. But it's still a shock to read that she passed away in 2019.
Way too young. Now to ponder cancer; she led a healthy lifestyle, only minimally partaking in the pot parties (part of the Coop House's budget!).
eco, I am so sorry to hear about your friend, Louise Kellogg. Quite an amazing person. It was a joy to read about her.
DeleteI was also said to hear of the passing of Eldridge M. Moore III's on the same UC-Davis page. He was Mr. Ophiolite!
One of the tributes to Louise resonated with me:
Delete"The educator within her would never give you the answer, but subtly nudge you down the right path without you realizing what she was doing."
And she attended Cornell for undergrad, too.
The name Louise Kellogg was stuck in my head. A little research showed she was an early American paleontologist. I recall reading her paper on rodents in Virgin Valley, NV. This Louise Kellogg lived from 1880 to 1967.
DeleteThat's an impressive memory deviation.
DeleteSlightly related (in that it's in my memory banks): have you ever wondered why Japanese Pagodas - tall, thin, with heavy roofs - don't fall down after centuries of frequent earthquakes? Years ago I clipped this article from The Economist, which explains the ingenious techniques.
Short version: I had always assumed they were designed like a tree, with a strong central post anchored in the ground, and the levels hanging off that. There is a central post that runs the height of the pagoda, but it does not carry any weight, and, in later versions of the pagoda from the 8th or 9th Century, the central pole is suspended from the roof, and barely touches the ground. And the heavy weight of the clay tile roofs, suspended high in the air, improve the performance, but only because of their unique shape. The Japanese builders anticipated modern seismic techniques by almost 1500 years.
I am all but certain I read an earlier (and better) explanation in Scientific American in the 1980's, but haven't found that article on line.
Ironically, modern codes in Japan would not permit this technique. Some engineering friends employed a modern version for a seismic retrofit of a 14 story building in SF.
Also ironic (and disappointing) was a conversion of an steel manufacturing plant that I was co-architect. The original steel skeleton was held together with rivets, and the exterior skin had corrugated steel panels that were only connected at the top. During an earthquake the building would sway from side to side, but the steel structure would not be damaged, and the skin would move like the scales on a fish or reptile, and return to their original place. Unfortunately we could not convince the city of the wisdom of this design, and had to spend hundreds of thousands of dollars to stiffen the building.
I thoroughly enjoyed The Economist article. Sorry the manufacturing plant did not ultimately have a skin with scales like a fish. It sounds beautiful and functional. And to scale ;-).
DeleteAs to the first Louise Kellogg, I wanted to read her paper because there weren't many women paleontologists writing papers in the U.S. (or anywhere) in 1910. I am thinking your Louise Kellogg must have run across her name at some point.
Just for the record, we didn't change the skin, the panels can still slide. But we did have to stiffen the framework with diagonal braces and expensive new footings.
DeleteTraditional Japanese building had no steel or iron for connectors, everything was carved wood. So they couldn't make stiff buildings, everything had to flex.
This would mean that interior walls would inevitably fall down, but that's not such a big deal if your wall is made out of rice paper, and becomes a movable screen. Of course those paper thin walls are not good for acoustic separation, and hence Japanese people have an incredible inherent courtesy and quietness in their domestic life.
It makes me wonder how much of Japanese culture was shaped by the realities of living on the fault line. As Winston Churchill once said, "We shape our buildings; thereafter they shape us." My inner megalomaniac yearns for such power.
I'm surprised that, with laser rangefinders being so available, you still have to dig a trench and drop in an engineer to determine just where a fault lies. (I know, not in our stars...)
ReplyDeleteGot me thinking about Oliver Sacks's Uncle Tungsten, and Wolfram Alpha.
Dropping engineers was what we loved doing at field camp. After all, they characterized a whole sedimentary suite of several million years as just "rock" on their stratigraphic charts.
DeleteThe Uncle Tungsten book looks intriguing as does the programming language.
Wolfram is a programming language, but Wolfram Alpha is (per Wikipedia) a computational knowledge engine or answer engine. It is an online service that answers factual queries directly by computing the answer from externally sourced "curated data", rather than providing a list of documents or web pages that might contain the answer, as a search engine might. I haven't used it much, but it seems interesting
DeleteWe know in general where the fault lies, but don't know precisely where there will be potential rupture/ movement of surface soil. So the rock stars have developed the Alquist-Priolo zone, roughly where the fault is. If you are in that area you have to determine the center, and then build where it won't slide in different directions, a very bad thing for your house.
DeleteFortunately the zone is fairly narrow, 50' is the no-build zone. I've only had a couple of projects that have "fallen" in that area. The zone runs the length of UC Berkeley's football field.
I appreciate my laser range finder, but it's not very good at detecting things under ground. And while there are various sonar detectors, I doubt any are sensitive enough to see the striations that show ground slippage in moderately consistent soil. Humans can still do things machines can't.
So far as I know the only way to see the fault is a pair of trained eyes looking for the anomalies and striations in the dirt layers. And you can't dig simple test holes as is done for determining foundation types - spread footings vs piers (and how deep). You're looking for a stripe that has moved.
I hadn't known about Cal's stadium. Could make for an interesting zig in the line of scrimmage.
Deletejan, the Wolfram Alpha suggestions are interesting. I wonder how many folks use it regularly.
ReplyDeleteeco, moving stripes? Sounds like the 70's. Did you intend for both links to go to the same video?
jan, the Cal video pointed me this way.
Of course the Cal Stadium issue is known around these parts, it hasn't been a big deal. Yet. The stripe on the field is clever, but a bit subtle when seen from Google Street View satellites. I've never been in the stadium, so I don't know how prominent it is in person. Probably the kind of thing you don't want your paying audience thinking about too much....
DeleteWhile one can't get too much Brian Eno, the first link was intended to go to the Alquist-Priolo website. I guess I didn't ctrl C hard enough.
Thanks for the new link!
DeleteI like the idea of a celestial autobahn. Too bad it still has that pesky 300,000 km/s speed limit.
ReplyDeleteJupiter, that dominant perturber! I can think of a human who holds that title, though I expect and hope less and less these next 17 days.
DeleteIt's surprising that the first probe to use a gravitational slingshot came just two years into the Space Age.
DeleteFunny thing about that human perturber: it has a very large mass and an eerily strong gravitational force. But the closer you get the more you are repulsed.
DeleteMeanwhile back on earth, monoliths have appeared in over 30 countries, including Columbus, San Antonio, Houston , Wisconsin, and India.
Perhaps it is a multilith?
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ReplyDeleteWhat a deranged group.
DeleteApparently the video was taken before the mob raid, hence my deletion. I saw an ambulance on one of the screens, and thought it was during the occupation.
DeleteBut they are still deranged.
No worries. I'd seen it before. That crowd-thumping "Gloria" music was so gross.
DeleteThe entirety is disgusting, and has been for years. My state's governor is mostly a reasonable man, but his previous marriage to Kimberly Guilfoyle has had me questioning his judgement.
DeleteAnd after last week's fiasco the right wingers will try to enact legislation that impedes peaceful protests.
They are loud, boorish and obnoxious—every single one of them.
DeleteI stayed up Thursday morning into the wee hours to be sure the votes were certified. It was quite moving to me.
I have talked to folks who said they don’t care about what is going on in Washington with the insurrection/invasion/riot as long as their kids get to go back to school Monday. My jaw dropped quite far on hearing that statement.
Good for you for staying up - I listened until they started the PA debate.
DeleteThey are worse than boorish, etc.; I think Trump's sadism has infected the lot of them. If they have power they take glee in the suffering of others (immigrant children, etc), in losing power they yearn for the destruction of all. As Germany was falling in 1945 Hitler (I know, a tired comparison) said that any citizen who hadn't fallen in fighting for the Reich did not deserve any protection. The psychologists will spend a lot of time writing about this one.
I wasn't worried about the immediate aftermath of Wednesday's events. It wasn't a coup, more a mob melee. One could argue Trump has been attempting a coup, but he had no support from the military. For me the question is whether this was the end of the beginning of a pathetic rebellion, or the beginning of the end from a revolution?
Revolutions are rarely successful in their first adventure, they build from smaller events. I'm hoping to hear from historians to put this into context. KPFA, my local public radio station (not part of NPR!) has an excellent program called Letters and Politics, I'm hoping they have an historical look at uprisings that both failed and resulted in later success.
I haven't spoken to the moronic sheep that you have; Berkeley is a happy (unhappy?) bubble.
I knew lava lamps had to be good for something.
ReplyDeleteLava it!
DeleteAnd that explains the tremendous crisis in San Francisco known as The Great Lava Lamp Lacuna. Haight Street has still not recovered.
Deleteeco, Lacuna reminds me of the film "Eternal Sunshine of the Spotless Mind." Any fellow fans out there in PEOTS Land?
DeleteI wonder if Lacuna could do something about these memories I have of the last four years?
DeleteThis might be the right musical moment.
DeleteYes!
DeleteWe almost saw Ella perform outdoors here in CO. A gully washer let loose cancelling her concert. We could have washed several folks out of our hair that evening.
Bummer on the Ella washout. Never saw her, but I did see Etta James perform in Oakland. Recently found this remarkable James Brown performance. What Michael Jackson wanted to be.
DeleteHave We Already Been Visited by Aliens?
ReplyDeleteIt might be the alien equivalent of an abandoned car, “floating in interstellar space” as “debris.”
Thanks, jan. I enjoyed that article and now have Oumuamua stuck in my brain. That word reminds me of umami.
DeleteCan no hole poke a big hole in a theory?
ReplyDeleteYou can deny it until you're blue in the face. Or red. But one look, and we know how you vote?
ReplyDeleteReminds me of the story my in-laws told about their first date. She was wearing a red coat. (Red meant something different back then.) He asked if her coat matched her politics. It did, They lived happily ever after.
Very surprising to me. Were some people wearing MAGA hats?
Delete(I came here to check out the disappearance of the delete button situation. I am going to write blogger about it.)
The DELETE function is back! Is it back for your posts as well?
DeleteI did write to Google to ask it be restored. Maybe they do listen!
DeleteYes. Thanks.
DeleteHere's my favorite New York Times milquetoast quote of the day, from their obit of George Carruthers, whose lightweight, gold-plated Far Ultraviolet Camera/Spectrograph John Young and Charlie Duke deployed on the Moon in 1972:
ReplyDelete"The device was left behind when the astronauts departed. Presumably it is still there."
Presumably? I'd like to hear the Times' theories on how it might possibly not be there!
I would, too.
DeleteIf you aren't a snake in the grass, well, it's the pits.
ReplyDeleteCool micrograph of snake skin.
DeleteGoats don't vote. It's hard to get those "I Voted" stickers to stick to their fur, anyway. No surprise, really. Cf, Bellwether, by Connie Willis. (Excellent book!)
ReplyDeleteThanks, jan. I ordered Willis's Bellwether from the library. Looks like a fun and interesting read.
ReplyDeleteThe great thing about The New Yorker is how often you can decide to start an article you think you have no interest in at all, and end up completely fascinated. I probably would have picked a different title than "How a Young Activist Is Helping Pope Francis Battle Climate Change", but you never know where you're going to find the next person who's going to change the world.
ReplyDeleteWow, jan, you were so right. That article went to all kinds of places of interest. Updating Catholic owned properties maps last updated in 1901, check. Talking to Jill Ker Conway, Smith's president, check. Mapping so many layers (including abuse by clergy) using GIS. Long article and worth every word. Thanks for sharing.
DeleteSeven Hundred Leagues Beneath Titan’s Methane Seas. The referenced JGR Planets paper on The Bathymetry of Moray Sinus at Titan's Kraken Mare, and the 102-page NASA Technical Memorandum on the proposed Titan Submarine are pretty cool.
ReplyDeleteAwesome stuff. Thanks, jan.
DeleteMartian Easter eggs!
ReplyDeleteOK, the moon has a tail. But why sodium? Why not something much more abundant on the moon? And, why sodium atoms? Metallic sodium doesn't exist on the lunar surface; why isn't all this meteoroid ejecta more common molecules?
ReplyDeleteWhy indeed!
DeleteMay is looking especially froggy
ReplyDelete<a href="https://www.nytimes.com/2021/03/18/us/storms-greek-alphabet.html>I said using the Greek alphabet to extend the annual list of hurricane names wouldn't fly.</a> Why not just number them? Hurricane 005, 006, 007, ...
ReplyDeleteWorks for me. Unless 007 hits Ochos Rios, Jamaica, mon.
DeleteMore on the Antikythera Mechanism, discussed here in 2014 and 2016. (Do you suppose this report is the newsworthy event that Unknown mentioned on Blaine's?)
ReplyDeleteWow, thanks, jan, so much to take in here. The Antikythera Mechanism is definitely my favorite mechanism.
DeleteAs to the newsworthy event Unknown mentioned at Blaine's, I'm still sorting that one out. Seems like it ought to be staring me in the face. . .
Iceland Volcano Stunning footage of the recent volcanic activity with folks just walking around.
ReplyDeleteNew basalt type: Rock on!
ReplyDeleteOK, today must be the day for GI tract radiography. First, you know the expression, to have one's heart in one's throat? Well, today's NEJM shows a lower part of the GI tract in one's heart. Then, NASA announced that astronomers have detected X-rays from Uranus for the first time. All of which, of course, led my inner third-grader to this.
ReplyDeleteWhy, just why?
DeleteWell, this is distressing: As if facial recognition software monitoring those ubiquitous video surveillance cameras isn't bad enough, now your DNA can be pulled out of thin air.
ReplyDeleteIt's so easy, even teens can do it. I know that birders can claim a "sighting" (for their "Big Year", e.g.) by just hearing a bird's call; maybe now they'll just need to sniff a DNA sample from the air.
New post on "Shoo, Shoo Shuvuuia: Nocturnal Owl-Like Dinosaur with Keen Eyesight and Acute Hearing" is now up. Whoosh, those 4 months flew on by!
ReplyDelete