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Reports on the Annals of the Former World

Recusant

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Reports on the Annals of the Former World
« on: May 02, 2020, 08:30:19 PM »
The title of this thread comes from the title of John McPhee's great book, Annals of the Former World. Though it examines the geology of North America, it's a superb description of the science of geology as well. It came to mind when I decided to make a thread for geology news. :)

Most recently, although already posted elsewhere:

"Japan Puts Its Mark on Geologic Time with the Chibanian Age" | Eos

Now this:

"Ancient Australian Rocks Suggest Earth's Continents Were Shifting Earlier Than Thought" | ScienceAlert

Quote
Earth's continents are constantly on the move, it's a key feature of our planet, but that wasn't always the case.

While some scientists think Earth's tectonic plates began pushing and pulling only a billion years ago, others think the whole process started nearly four billion years ago, when our planet was but an infant.

That's quite the discrepancy, and as usual, general agreement lies somewhere in between. Today, it's commonly thought Earth's tectonic plates began moving around 2.8 billion years ago, when the interior of our planet was just the right temperature to allow for the formation of 15 rigid plates.

Even still, disagreement reigns. Direct evidence from this time is hard to come by, and now some of the oldest rocks on Earth suggest we may have been more than 400 million years off the mark.

Analysing magnetism in ancient rocks from Australia and South Africa, researchers at Harvard and MIT claim tectonic plates were moving at least 3.2 billion years ago and maybe earlier.

"Basically, this is one piece of geological evidence to extend the record of plate tectonics on Earth farther back in Earth history," says Alec Brenner, who researches paleomagnetics at Harvard University.

"Based on the evidence we found, it looks like plate tectonics is a much more likely process to have occurred on the early Earth and that argues for an Earth that looks a lot more similar to today's than a lot of people think."

The Pilbara craton in Western Australia is one of the oldest slices of Earth's ancient crust and contains fossils for some of the earliest organisms on our planet. Stretching nearly 500 kilometres across (300 miles), this chunk of primordial crust was formed as early as 3.5 billion years ago.

Drilling into a portion of this craton, known as the Honeyeater Basalt, researchers used state of the art magnetometers and demagnetising equipment to uncover the region's magnetic history.

Roughly 3.2 billion years ago, their data reveals a shift from one point to another, a latitudinal drift of 2.5 centimetres a year.

Or, as the authors put it, "a velocity comparable with those of modern plates."

[Continues . . .]

The paper is linked in the final paragraph above.
"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken


Tank

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Re: Reports on the Annals of the Former World
« Reply #1 on: May 06, 2020, 06:37:52 AM »
I missed this! I have to say that with my layman's understanding of plate tectonics (Dunning Krugar warning) that I would have thought that when the Earth was younger and hotter plate tectonics would have been more active than now.
If religions were TV channels atheism is turning the TV off.
“Religion is a culture of faith; science is a culture of doubt.” ― Richard P. Feynman
'It is said that your life flashes before your eyes just before you die. That is true, it's called Life.' - Terry Pratchett
Remember, your inability to grasp science is not a valid argument against it.

Recusant

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Re: Reports on the Annals of the Former World
« Reply #2 on: May 15, 2020, 05:57:16 AM »
I missed this! I have to say that with my layman's understanding of plate tectonics (Dunning Krugar warning) that I would have thought that when the Earth was younger and hotter plate tectonics would have been more active than now.

That seems reasonable to me as well. I'm not privy to the line of thinking which would make it likely that there was a more recent (in geological time) start to tectonic movement in the Earth's crust.
"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken


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Re: Reports on the Annals of the Former World
« Reply #3 on: May 15, 2020, 06:04:23 AM »
New hypothesis on the Great Uncomformity of the Grand Canyon and similar uncomformities around the world.

"A billion years missing from geologic record: Where it may have gone" | ScienceDaily

Quote
The geologic record is exactly that: a record. The strata of rock tell scientists about past environments, much like pages in an encyclopedia. Except this reference book has more pages missing than it has remaining. So geologists are tasked not only with understanding what is there, but also with figuring out what's not, and where it went.

One omission in particular has puzzled scientists for well over a century. First noticed by John Wesley Powell in 1869 in the layers of the Grand Canyon, the Great Unconformity, as it's known, accounts for more than one billion years of missing rock in certain places.

Scientists have developed several hypotheses to explain how, and when, this staggering amount of material may have been eroded. Now, UC Santa Barbara geologist Francis Macdonald and his colleagues at the University of Colorado, Boulder and at Colorado College believe they may have ruled out one of the more popular of these. Their study appears in the Proceedings of the National Academy of Sciences.

"There are unconformities all through the rock record," explained Macdonald, a professor in the Department of Earth Science. "Unconformities are just gaps in time within the rock record. This one's called the Great Unconformity because it was thought to be a particularly large gap, maybe a global gap."

A leading thought is that glaciers scoured away kilometers of rock around 720 to 635 million years ago, during a time known as Snowball Earth, when the planet was completely covered by ice. This hypothesis even has the benefit of helping to explain the rapid emergence of complex organisms shortly thereafter, in the Cambrian explosion, since all this eroded material could have seeded the oceans with tremendous amounts of nutrients.

Macdonald was skeptical of this reasoning. Although analogues of the Great Unconformity appear throughout the world -- with similar amounts of rock missing from similar stretches of time -- they don't line up perfectly. This casts doubt as to whether they were truly eroded by a global event like Snowball Earth.

[. . .]

"The basic hypothesis is that this large-scale erosion was driven by the formation and separation of supercontinents," Macdonald said.

The Earth's cycle of supercontinent formation and separation uplifts and erodes incredible extents of rock over long periods of time. And because supercontinent processes, by definition, involve a lot of land, their effects can appear fairly synchronous across the geologic record.

However, these processes don't happen simultaneously, as they would in a global event like Snowball Earth. "It's a messy process," Macdonald said. "There are differences, and now we have the ability to perhaps resolve those differences and pull that record out."

[Continues . . .]
"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken


Recusant

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Re: Reports on the Annals of the Former World
« Reply #4 on: May 16, 2020, 04:12:37 AM »
Trying to understand a place where our ancestors used to live. Though I think this one may be under deeper water, the story below reminded me of Doggerland. It's an impressive effort. These scientists appear confident in their modelling, and perhaps the confidence is justified.

"Early humans thrived in this drowned South African landscape" | ScienceDaily


The southern tip of Africa. Dotted line offshore shows the extent of the Paleo-Agulhas Plain during the last glacial maximum.
Image Credit: J. Sealy et al. / Quaternary Science Reviews

Quote
Scientists have reconstructed the paleoecology the Paleo-Agulhas Plain, a now-drowned landscape on the southern tip of Africa that was high and dry during glacial phases of the last 2 million years and may have been instrumental in shaping the evolution of early modern humans.

Early humans lived in South African river valleys with deep, fertile soils filled with grasslands, floodplains, woodlands, and wetlands that abounded with hippos, zebras, antelopes, and many other animals, some extinct for millennia.

In contrast to ice age environments elsewhere on Earth, it was a lush environment with a mild climate that disappeared under rising sea levels around 11,500 years ago.

An interdisciplinary, international team of scientists has now brought this pleasant cradle of humankind back to life in a special collection of articles that reconstruct the paleoecology of the Paleo-Agulhas Plain, a now-drowned landscape on the southern tip of Africa that was high and dry during glacial phases of the last 2 million years.

"These Pleistocene glacial periods would have presented a very different resource landscape for early modern human hunter-gatherers than the landscape found in modern Cape coastal lowlands, and may have been instrumental in shaping the evolution of early modern humans," said Janet Franklin, a distinguished professor of biogeography in the department of Botany and Plant Sciences at UC Riverside, an associate member of the African Centre for Coastal Palaeoscience at Nelson Mandela University in South Africa, and co-author of several of the papers.

Some of the oldest anatomically modern human bones and artifacts have been found in cliff caves along the coast of South Africa. For many years, the lack of shellfish in some layers at these sites puzzled archaeologists. In spite of apparently living near the ocean, the inhabitants hunted mostly big game -- the sort of animals that typically live farther inland.

Scientists knew a submerged landscape existed on the continental shelf just offshore, but it wasn't until recently, perhaps inspired by rising sea levels of our current human-caused global warming, they realized these caves might have made up the westernmost edge of a long-lost plain.

During most of the Pleistocene, the geological era before the one we live in now, these caves were not located on the coast. With so much of the Earth's water locked up in continent-sized glaciers, sea level was much lower, and humans could have thrived between the cliffs and a gentler coastline miles and miles to the east.

A special issue of Quaternary Science Reviews presents papers using a wide range of techniques to reconstruct the environment and ecology of the Paleo-Agulhas Plain. They reveal a verdant world rich with game, plant, and coastal resources, periodically cut off from the mainland during warm spells between glacial periods when sea level rose to levels similar to those of today, which would have played an important role in human evolution.

[Continues . . .]

Two of the papers are open access.
« Last Edit: May 22, 2020, 04:37:15 AM by Recusant »
"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken


Tank

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Re: Reports on the Annals of the Former World
« Reply #5 on: May 16, 2020, 06:12:39 AM »
Oh for a time machine :(
If religions were TV channels atheism is turning the TV off.
“Religion is a culture of faith; science is a culture of doubt.” ― Richard P. Feynman
'It is said that your life flashes before your eyes just before you die. That is true, it's called Life.' - Terry Pratchett
Remember, your inability to grasp science is not a valid argument against it.

Recusant

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Re: Reports on the Annals of the Former World
« Reply #6 on: May 22, 2020, 04:53:37 AM »
Well, this one is about something that's going on right now. It's on the wandering north magnetic pole, which has been moving more quickly of late.

Out of curiosity, I checked on what the south magnetic pole is doing, and though it does wander, it hasn't been exhibiting the same changes. Moreover, the south magnetic pole is much further from the geographical south pole than the north magnetic pole is from the geographical north pole. ("Wandering of the Geomagnetic poles" | NOAA National Centers for Environmental Information)

Back to the real purpose of this post:

"Earth's Magnetic North Is Moving From Canada to Russia, And We May Finally Know Why" | ScienceAlert

Quote
Our planet wears its magnetic field like an oversized coat that just won't sit comfortably. All that sliding means the north magnetic pole is destined to move ever closer to Siberia's coastline over the coming decade.

There's no conspiracy behind it - but the geological forces responsible have been something of a mystery. Now, we might be a little closer to understanding what's going on.

Researchers from the University of Leeds in the UK and the Technical University of Denmark have analysed 20 years of satellite data, finding that a monolithic competition between two lobes of differing magnetic force near the core is likely to be behind the pole's wanderlust.   

When the precise position of Earth's magnetic north was located for the first time back in 1831, it was squarely in Canada's corner of the Arctic, on the Boothia Peninsula in the territory of Nunavut.

Ever since, fresh sets of measurements have recorded this spot drift north by an average of around 15 kilometres (about 9 miles) every year.

Advanced technology means we can now keep a careful watch on the pole's location with unprecedented accuracy. Prior to the 1970s, the north magnetic pole's position was like a drunken stagger. Since then, it's had a mission, marching in a straight line, building speed.

Since the 1990s, its movement has quadrupled in speed, to a current rate of between 50 and 60 kilometres (about 30 and 37 miles) a year. In late 2017, the pole's sprint brought it within 390 kilometres (240 miles) of the geographical north pole.

[Continues . . .]
"Religion is fundamentally opposed to everything I hold in veneration — courage, clear thinking, honesty, fairness, and above all, love of the truth."
— H. L. Mencken


Randy

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Re: Reports on the Annals of the Former World
« Reply #7 on: May 22, 2020, 03:30:34 PM »
Oh for a time machine :(

Billy Rubin's wife might be able to make one out of zip ties.
"Maybe it's just a bunch of stuff that happens." -- Homer Simpson

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Re: Reports on the Annals of the Former World
« Reply #8 on: May 22, 2020, 07:54:22 PM »
and push pins


Into the distance a ribbon of black
Stretched to the point of no turning back
A flight of fancy on a windswept field
Standing alone my senses reeled
A fatal attraction is holding me fast how
How can I escape this irresistible grasp?

hermes2015

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Re: Reports on the Annals of the Former World
« Reply #9 on: May 23, 2020, 06:22:36 AM »
I've been to a large nature reserve in that beautiful area. There is an air monitoring lab with gas chromatographs, and I went there once to train them to measure SF6 (sulphur hexafluoride) in the atmosphere. Air samples are drawn in from a tall tower and fed into a gas sampling loop in the GC for measurement.

https://www.google.com/search?sxsrf=ALeKk02rVpGd6WAY8WCF-saBXbnUNFOi0A:1590211412880&source=univ&tbm=isch&q=nature+reserve+southern+tip+of+africa&sa=X&ved=2ahUKEwi_p4eTn8npAhWEyKQKHW0eDdYQ7Al6BAgKEC4&biw=1876&bih=936
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Icarus

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Re: Reports on the Annals of the Former World
« Reply #10 on: May 24, 2020, 12:57:15 AM »
Holy cow Hermes!  That link is spectacular.  Not so much about the chemistry but about the whole bit of beautiful SA information.

Most of we dullard Americans envision Africa as a place where Hutus and Tutsi kill each other.  I know better but your link has made me think of that continent in a different way.

As a matter of fact an Amrerican doctor lives across the street from me. He got some of his Med education in SA. His wife is a very charming South African woman who is entirely civilized and sophisticated.

A Brit friend who was here for a while once, when in a philosophic and wine fueled discussion, said this to me: "Americans are so insular".  That statement stuck in my brain to this day. He was polite enough not to tell me that a lot of Americans are ill informed clods. He was correct of course.

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Re: Reports on the Annals of the Former World
« Reply #11 on: May 24, 2020, 04:07:46 AM »
Holy cow Hermes!  That link is spectacular.  Not so much about the chemistry but about the whole bit of beautiful SA information.

Most of we dullard Americans envision Africa as a place where Hutus and Tutsi kill each other.  I know better but your link has made me think of that continent in a different way.

As a matter of fact an Amrerican doctor lives across the street from me. He got some of his Med education in SA. His wife is a very charming South African woman who is entirely civilized and sophisticated.

A Brit friend who was here for a while once, when in a philosophic and wine fueled discussion, said this to me: "Americans are so insular".  That statement stuck in my brain to this day. He was polite enough not to tell me that a lot of Americans are ill informed clods. He was correct of course.

"Insular"? The rest of the world's people only have to look at the kind of people who voted for the chump to see that (among other indicators). It is a huge portion of the US' population, sad to say. I also will observe that people who have to live "up against" other people who have vastly different political opinions, like in Europe, reduces that insular behavior.
This chisel type is called a "skew". I ask you, do I seem a little askew?

Icarus

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Re: Reports on the Annals of the Former World
« Reply #12 on: May 24, 2020, 10:13:55 PM »
That word, insular, was to imply that we see our country as an island of brilliant, productive, inspired, and generally better than the rest of the world.   We are on a really big island, separated from a lot of other countries by large oceans. Our AMERICA IS NUMBER ONE mind set misses the mark of course, but it works for a lot of us.   

Randy

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Re: Reports on the Annals of the Former World
« Reply #13 on: May 25, 2020, 01:21:30 AM »
That was one of the things I liked about working in an office. I usually ended up meeting someone from out of the country. I also got to travel to the UK a few times and work with my team. I'd learn a lot about how the USA is viewed. Many were engaged talking to me and having me explain a few things. I also lived in Germany for three years when I was in elementary school.

I traveled to the Philippines for two weeks once and got to enjoy the customs and the dialog we'd share, including getting completely drunk off a $1.00 bottle of rum made there. I was the only one of the group who didn't have a hangover which surprised me.

I met a doctor who believed in ghosts for instance and quite a few believe that witchcraft is real.

But I'm digressing and I didn't mean to hijack the thread. What I wanted to get to is that so many never travel abroad and talk to the natives. There is so much to be gained by sitting at the dinner table and talking.
"Maybe it's just a bunch of stuff that happens." -- Homer Simpson

Dark Lightning

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Re: Reports on the Annals of the Former World
« Reply #14 on: May 25, 2020, 01:29:42 AM »
That word, insular, was to imply that we see our country as an island of brilliant, productive, inspired, and generally better than the rest of the world.   We are on a really big island, separated from a lot of other countries by large oceans. Our AMERICA IS NUMBER ONE mind set misses the mark of course, but it works for a lot of us.   

I understand that. :smilenod: What I like about this country is when I worked as an engineer and we had people from all over the world working in cooperation. They know how it can be elsewhere, from the outside, and really lied living in the US. Melting pot, for sure. I worked with a lot of US citizens who were only in it for themselves. Really disappointing. Those "Dark Personalities", as discussed in another thread.
This chisel type is called a "skew". I ask you, do I seem a little askew?