Continental drift (Introduction)
by David Turell 
, Tuesday, January 10, 2012, 01:30 (4702 days ago)
From pangea til now. Plate techtonics was not accepted until the middle of the last century:
http://blogs.scientificamerican.com/history-of-geology/2012/01/06/january-6-1912-contin...
Continental drift
by David Turell , Saturday, June 02, 2012, 20:15 (4558 days ago) @ David Turell
Plate techtonics only explain the past 3 billion years. The 1.7 billion years before that of crustal activity needs a new theory.- http://www.sciencedaily.com/releases/2012/06/120601120606.htm
Continental drift
by David Turell , Friday, September 22, 2017, 14:06 (2620 days ago) @ David Turell
Without it there would be no life. It is understood but the start is not fully explained:
file:///C:/Users/pacemaker/AppData/Local/Packages/Microsoft.MicrosoftEdge_8wekyb3d8bbwe...
From page 54 0n:
"NOT ONLY DOES EARTH LIE in the ‘Goldilocks zone’ that allows water to exist in the liquid form that life requires. It is also the only rocky planet we know of that constantly renovates its surface as its tectonic plates dive into the mantle in some places and re-emerge as molten lava in others. Many astrobiologists now think this constant renewal is just as important as liquid water for the flourishing of life as we know it. The theory, explains planetary scientist Adrian Lenardic of Rice University in Houston, Texas, is that the Earth’s climate has been buffered by the recycling of carbon dioxide (CO2) from the atmosphere into the planet’s interior via mineral sequestration and then out again via volcanoes. This has kept the climate temperate even as the Sun’s heat has increased in intensity by about a third since the planet’s birth. Without this buffering, Earth might have heated so much that all the water in its oceans boiled away and huge quantities of CO2 accumulated in the atmosphere, much like Venus which has an average temperature of 462 o C. Or it might never have recovered from being a snowball, remaining permanently frozen. Among the rocky worlds we know, Earth’s tectonics are unique. Venus and Mercury have no similar geological activity. Mars might have once, but not for billions of years. So why are we so lucky? According to geophysicist David Bercovici, of Yale University, models show the Earth sits right on the cusp between being a world with plate tectonics and one with a ‘stagnant lid’, like modern-day Mars or Venus. Something must have kicked it in the direction that produced a geologically active world that eventually gave birth to us. Bizarrely, even as astronomers probe planets hundreds of light-years distant, geologists still can’t precisely explain what triggered the events taking place beneath our feet.
***
"In this process, continents tend to remain on the surface. They are too buoyant to be easily subducted into the depths. But they still play an important role via a process known as ‘weathering’, which provides a vital thermostat that has helped keep the Earth temperate for billions of years. It begins when CO2 from the atmosphere dissolves in rainwater to form carbonic acid. This breaks down minerals in continental rocks, producing calcium and bicarbonate ions that wash into the sea. Marine organisms take them up to form calcium carbonate, the building block for their shells and skeletons, which ultimately settle to the seafloor and become limestone. Each year the process removes about 300 million tonnes of CO2 from the atmosphere. But the carbon isn’t sequestered forever, because some of that limestone is subducted along with the seabed. It heats, melts and is incorporated into magma for carbon dioxide-spewing volcanoes to release. This also produces fresh rock for the next weathering cycle. What makes this process function like a thermostat is that the more CO2 there is in the atmosphere, the more carbonic acid there is in rain (and the more rapidly weathering occurs). This removes CO2 from the atmosphere more swiftly, keeping the Earth from transforming into a Venusian runaway greenhouse. Conversely, if atmospheric CO2 levels fall,weathering slows, allowing volcanic CO2 to slowly build back up. It’s a slow, self-correcting process that for billions of years has kept the Earth’s temperature within a zone that is hospitable to life.
***
"IF THERE’S ANY CONSENSUS amongst geologists, it is that something changed about 2.7 billion years ago to kick tectonic plates into action. “There appears to have been a major event,” says Kent Condie, a geochronologist at the New Mexico Institute of Mining and Technology in Socorro. But what could that have been? Theories range from the mundane to the dramatic, but all require the Earth to have overcome the same basic hurdles. Either the power of the lava lamp that makes mantle currents rise and swirl must have increased or the Earth’s crust must have weakened, allowing it to break into plates; or perhaps both occurred simultaneously.
***
"IT IS EASY TO try to fold all of this into a nice, coherent story. It would begin with a magma ocean, followed by weak, intermittent plume-style tectonics. These would eventually reach some tipping point that shifted the process to its present state, either due to changes in the core, an asteroid impact, the accumulation of Bercovici’s weak spots, or some combination of all three. But the plethora of options suggests caution. We may not yet have all the pieces to the puzzle. "
Comment: The entire article is worth the read, especially the illustrations. I've mentioned three books that cover this subject. The Earth is very special, so unusual it appears to be designed for the purpose of creating life. Rare Earth and Privileged Planet are two of the books.
Continental drift: tectonic activity from 3.5 bya
by David Turell , Friday, September 22, 2017, 18:31 (2620 days ago) @ David Turell
A new study using titanium finds tectonic activity started 3.5 billion years ago:
https://phys.org/news/2017-09-analysis-titanium-ancient-upheaval-history.html
"A new study led by UChicago geochemists rearranges the picture of the early Earth by tracing the path of metallic element titanium through the Earth's crust across time. The research, published Sept. 22 in Science, suggests significant tectonic action was already taking place 3.5 billion years ago—about half a billion years earlier than currently thought.
***
"Dauphas and his team looked at titanium in the shales over time. This element doesn't dissolve in water and isn't taken up by plants in nutrient cycles, so they thought the data would have fewer biases with which to contend.
"They crushed samples of shale rocks of different ages from around the world and checked in what form its titanium appeared. The proportions of titanium isotopes present should shift as the rock changes from mafic to felsic. Instead, they saw little change over three and a half billion years, suggesting that the transition must have occurred before then.
"This also would mark the beginning of plate tectonics, since that process is believed to be needed to create felsic rock.
***
"The question about nutrients is important for our understanding of the circumstances around a mysterious but crucial turning point called the great oxygenation event. This is when oxygen started to emerge as an important constituent of Earth's atmosphere, wreaking a massive change on the planet—and making it possible for multi-celled beings to evolve.
"The flood of oxygen came from a surge of photosynthetic microorganisms; and in turn their work was fostered by a surge of nutrients to the oceans, particularly phosphorus. "Phosphorus is the most important limiting nutrient in the modern ocean. If you fertilize the ocean with phosphorus, life will bloom," Dauphas said.
"The titanium timeline suggests that the primary trigger of the surge of phosphorus was the change in the makeup of mafic rock over time. As the Earth cooled, the mafic rock coming out of volcanoes and underground melts became richer in phosphorus.
"'We've known for a long time that mafic rock changed over time, but what we didn't know was that their contribution to the crust has stayed rather consistent," Ptáček said."
Comment: If God uses evolutionary processes, to create a complex-life-giving Earth, He certainly started early enough.
Continental drift: tectonic activity review article
by David Turell , Wednesday, December 27, 2017, 15:23 (2524 days ago) @ David Turell
A very long history of the science of plate tectonics. Without it life would not exist on Earth. We appear to b e a most unusual planet:
https://cosmosmagazine.com/geoscience/plate-tectonics-the-hidden-key-to-life-on-earth
"Not only does Earth lie in the ‘Goldilocks zone’ that allows water to exist in the liquid form that life requires. It is also the only rocky planet we know of that constantly renovates its surface as its tectonic plates dive into the mantle in some places and re-emerge as molten lava in others. Many astrobiologists now think this constant renewal is just as important as liquid water for the flourishing of life as we know it.
"The theory, explains planetary scientist Adrian Lenardic of Rice University in Houston, Texas, is that the Earth’s climate has been buffered by the recycling of carbon dioxide (CO2) from the atmosphere into the planet’s interior via mineral sequestration and then out again via volcanoes. This has kept the climate temperate even as the Sun’s heat has increased in intensity by about a third since the planet’s birth. Without this buffering, Earth might have heated so much that all the water in its oceans boiled away and huge quantities of CO2 accumulated in the atmosphere, much like Venus which has an average temperature of 462°C. Or it might never have recovered from being a snowball, remaining permanently frozen.
"Among the rocky worlds we know, Earth’s tectonics are unique. Venus and Mercury have no similar geological activity. Mars might have once, but not for billions of years. So why are we so lucky?
"According to geophysicist David Bercovici, of Yale University, models show the Earth sits right on the cusp between being a world with plate tectonics and one with a ‘stagnant lid’, like modern-day Mars or Venus. Something must have kicked it in the direction that produced a geologically active world that eventually gave birth to us. Bizarrely, even as astronomers probe planets hundreds of light-years distant, geologists still can’t precisely explain what triggered the events taking place beneath our feet.
***
"The plates do not move in the same direction or at the same speed. This causes some plates to crash into each other, driving up mountain ranges, such as the Himalayas at the collision of the Indian and Eurasian plates. They can also grind past one another, as along California’s famed San Andreas Fault. Or one can dive beneath another, as occurs at the Pacific ‘Ring of Fire’ that circles the Pacific Ocean in a belt of earthquake-prone regions and volcanic activity.
"In this process, continents tend to remain on the surface. They are too buoyant to be easily subducted into the depths. But they still play an important role via a process known as ‘weathering’, which provides a vital thermostat that has helped keep the Earth temperate for billions of years.
***
"It begins when CO2 from the atmosphere dissolves in rainwater to form carbonic acid. This breaks down minerals in continental rocks, producing calcium and bicarbonate ions that wash into the sea. Marine organisms take them up to form calcium carbonate, the building block for their shells and skeletons, which ultimately settle to the seafloor and become limestone.
"Each year the process removes about 300 million tonnes of CO2 from the atmosphere. But the carbon isn’t sequestered forever, because some of that limestone is subducted along with the seabed. It heats, melts and is incorporated into magma for carbon dioxide-spewing volcanoes to release. This also produces fresh rock for the next weathering cycle.
"What makes this process function like a thermostat is that the more CO2 there is in the atmosphere, the more carbonic acid there is in rain (and the more rapidly weathering occurs). This removes CO2 from the atmosphere more swiftly, keeping the Earth from transforming into a Venusian runaway greenhouse. Conversely, if atmospheric CO2 levels fall, weathering slows, allowing volcanic CO2 to slowly build back up. It’s a slow, self-correcting process that for billions of years has kept the Earth’s temperature within a zone that is hospitable to life."
Comment: The rest of the article tries to explain what is known about how it all happened. The earth is certainly unique. Designed by God?
Continental drift: part of Canada in Australia
by David Turell , Wednesday, January 24, 2018, 00:58 (2496 days ago) @ David Turell
A supercontinent called Nuna existed 1.7 billion years ago and when it broke up a piece of Canada hooked up with Australia. Pangia was a supercontinent 175 million years ago.
http://www.newsweek.com/piece-north-america-found-australia-bolsters-theory-two-billion...
Scientists recently discovered a region of Australia that was once part of North America, bolstering support for the idea that the two existed as a unified 'supercontinent' nearly two billion years ago.
A team led by researchers from Curtin University in Australia discovered that the sedimentary sandstone in the northern Australian region of Georgetown didn't bear much resemblance to other rock compositions in Australia, according to a Curtin University press statement. It did, however, bear quite a strong resemblance to rocks one might find in the North American landmass, known as Laurentia.
This was a critical part of global continental reorganisation when almost all continents on Earth assembled to form the supercontinent called Nuna," co-author Adam Nordsvan, a student at Curtin University's School of Earth and Planetary Sciences, said in the press statement.
The most well-known supercontinent, Pangea, broke apart sometime around 175 million years ago, according to Live Science. But while Pangea may be the most famous, it wasn't the first; a number of supercontinents came before it, including Nuna (sometimes referred to as the Columbia supercontinent).
Nuna itself split into pieces another 300 million years after reaching Australia, according to the statement. But even as the rest of the landmass drifted away, the rock under what would later become Georgetown refused to budge, and has remained part of Australia ever since.
Researchers first started compiling evidence for Nuna's existence in 2002, according to a separate report from Live Science. While the scientific community believed that the landmass under northeast Australia had once been situated by North America, northern China or Siberia, there was never sufficient geological data to prove it. This is a big contribution to the body of evidence supporting Nuna.
“Ongoing research by our team shows that this mountain belt, in contrast to the Himalayas, would not have been very high, suggesting the final continental assembling process that led to the formation of the supercontinent Nuna was not a hard collision like India’s recent collision with Asia,” co-author Zheng-Xiang Li, a John Curtin Distinguished Professor in the School of Earth and Planetary Sciences, said in the press statement. “This new finding is a key step in understanding how Earth’s first supercontinent Nuna may have formed.”
Comment: Our continental crust is light and floats around, and has been doing so for almost two billion years. Continental drift has been an accepted theory for only 60 years, and evidence for Nuna is only 16 years old. A rapid advance for geology. Subduction is vital for the carbon dioxide cycle to exist. It is part of the unique processes that make Earth a special place for life.
Continental drift: supercontinent before Pangea
by David Turell , Wednesday, March 24, 2021, 18:27 (1341 days ago) @ David Turell
Possibly found:
https://phys.org/news/2021-03-clues-earth-supercontinent.html
"Curtin University research has uncovered the first solid clues about the very beginning of the supercontinent cycle of Earth, finding it was kick-started two billion years ago.
"Detailed in a paper published in Geology, a team of researchers from Curtin's Earth Dynamics Research Group found that plate tectonics operated differently before two billion years ago, and the 600 million years supercontinent cycle likely only started during the second half of Earth's life.
***
"'Pangea was the first supercontinent scientists discovered early last century that existed some 300 million years ago and lasted until the age of the dinosaurs. Geologists realised more recently that at least two older supercontinents existed before Pangea in the past two billion years (Ga) in a 600 million year cycle. But what happened in the first 2.5 billion years of Earth's history is anybody's guess."
"'Our research was essentially testing two hypotheses—one is that the supercontinent cycle started prior to two billion years ago. Alternatively, the ancient continents (called cratons) only managed to get together in multiple clusters called supercratons, instead of forming a singular supercontinent."
***
"'By precisely dating the rocks and measuring the samples' magnetic record, using a technique called palaeomagnetism, we are able to reconstruct where those rocks were (relative to the magnetic North pole) when they formed," Dr. Liu said.
"Co-author John Curtin Distinguished Professor Zheng-Xiang Li, from Curtin's School of Earth and Planetary Sciences, said by analysing their new data from Yilgarn, and comparing it with data available globally for other cratons, one thing became clear.
"'It was clear that we can almost rule out the existence of a long-lived single supercontinent before two billion years ago (2 Ga), although transient supercontinents may have existed" Professor Li said.
"'More likely, there could have been two long-lived clusters of cratons, or supercratons, before 2 Ga that were geographically isolated from each other, never forming a singular supercontinent.'"
Comment: The formation of continents allowed land organisms to develop. But obviously since life is about 3.8 bya life developed under water, unless there were cratons where life developed.
Continental drift: plate tectonics from 3.2 bya
by David Turell , Thursday, March 25, 2021, 19:39 (1340 days ago) @ David Turell
The earliest evidence of plate tectonics found in studies of western Australian rock:
https://www.quantamagazine.org/ancient-rocks-reveal-when-earths-plate-tectonics-began-2...
"Tungsten-182 should be relatively abundant in rocks from early in Earth’s history. Once plate tectonics started, however, the convective churning of the mantle would have mixed up tungsten-182 with the other four isotopes of tungsten, yielding rocks with uniformly low tungsten-182 values.
***
"The tungsten-182 concentrations started out high in rocks formed before 3.3 billion years ago, showing that the mantle wasn’t mixing yet. Then the values declined over 200 million years until they reached modern levels by 3.1 billion years ago. That decline reflects the dilution of the ancient tungsten-182 signal as the mantle beneath Pilbara began to mix. That mixing shows plate tectonics had begun.
***
"The tungsten-182 concentrations started out high in rocks formed before 3.3 billion years ago, showing that the mantle wasn’t mixing yet. Then the values declined over 200 million years until they reached modern levels by 3.1 billion years ago. That decline reflects the dilution of the ancient tungsten-182 signal as the mantle beneath Pilbara began to mix. That mixing shows plate tectonics had begun.
"Earth would quickly transform from a water world studded with Iceland-like volcanic islands into a world of continents with mountains, rivers and floodplains, lakes, and shallow seas.
***
"Life started beforehand, more than 3.9 billion years ago, and was making hummocky little stacks in sediments at Pilbara called stromatolites by 3.48 billion years ago. This shows that plate tectonics isn’t a prerequisite for life at its most basic level. Yet it’s probably no coincidence that life diversified just as plate tectonics got underway. (my bold)
"With plate tectonics came shallow sunlit seas and lakes fertilized with nutrients weathered from continental rock. Bacteria evolved in these environments to harvest sunlight through photosynthesis, generating oxygen.
***
"Gradually, though, plate tectonics provided the land and sediments in which to bury more and more of the carbon (while also providing plenty of phosphorus to stimulate photosynthetic bacteria). The atmosphere eventually oxygenated 2.4 billion years ago.
***
"Progress toward complexity stalled during the “boring billion” era, the roughly billion-year reign of the supercontinent Nuna-Rodinia. With the continents stuck in a jam, Ming Tang of Peking University and colleagues argue, mountains eroded completely, reducing the flow of nutrients into the ocean and lowering oxygen levels.
"Eventually the supercontinent broke apart, and new mountains grew and exported nutrients again. Only then — around 600 million years ago — did complex organisms diversify and get bigger, riding Earth’s second rise in oxygen.
"Complex animal life exploded in the oceans 540 million years ago, and on land soon after. Dry land was now habitable because oxygen in the stratosphere formed ozone that protected land life from ultraviolet radiation."
Comment: All the chemical cycles from the effects of plate tectonics, that provide for life, have been described, but now we know when it began. It now appears life to start did not need plate tectonics, but to advance and complexify, continuing tectonics are vital.
Continental drift: how it works
by David Turell , Tuesday, February 08, 2022, 01:22 (1020 days ago) @ David Turell
Both drift and magmas pressures:
https://phys.org/news/2022-02-tectonic-plates-formation-rifts.html
"The new study was published in November 2021. It describes how a trench-like structure called a rift-graben opened in 2014 in Iceland near what is now known as the Holuhraun lava field, in a region that straddles the tectonic boundary between the North American and Eurasian plates. A graben forms when a chunk of land sags downward as the land on both sides of it moves away, creating a chasm called a rift.
"The team concluded that in this particular case, the slow drift of tectonic plates, and not pressure from a magma chamber along the rift, was the driver.
"The graben formed within a period of a few days, and then, "it just stayed like that, and it didn't care about anything else that happened in the magmatic plumbing system," Kolzenburg says. "The graben was remarkably stable even though lots of dynamic processes were happening underneath, such as pressure changes in the magmatic feeder system of the eruption."
"Magma leaked through the rift once it was open, but that magma didn't appear to be the main force behind the initial creation of the rift, Kolzenburg says.
***
"The findings apply specifically to the graben the team studied. In other rift zones, different dynamics may be at play, including in the Afar Region of Ethiopia, where magma is believed to play a more important role in driving rift formation, Kolzenburg says.
"As he and co-authors write in their 2021 paper in Geology, "In concert, the data suggest that while some rifts may be magmatically controlled, not all rift zones require the presence of a deep-seated pressurized magma chamber to control their dynamics."
Comment: no matter how it works, because continents drift and subduct conditions for life are established on this Privileged Planet
Continental drift: major cause for life to appear
by David Turell , Saturday, July 06, 2024, 15:11 (141 days ago) @ David Turell
Reduces odds for life elsewhere:
https://www.universetoday.com/167659/plate-tectonics-might-only-occur-on-0-003-of-plane...
"Plate tectonics, oceans, and continents might just be the secret ingredients for complex life on Earth. And if these geological features are rare elsewhere in the universe, then perhaps that explains why we haven’t yet discovered intelligent alien life. New research from American and Swiss Earth scientists suggests that these ingredients represent missing variables in the famous Drake equation, devised more than half a century ago to estimate the chances of finding advanced civilizations in our galaxy. Including these new variables could completely rewrite the probability of detecting intelligent life in the Milky Way.
"The impetus for this research, with its galaxy-spanning implications, began with a mystery right here at home – why did life take so long to move beyond simple organisms?
“'Life has been around on Earth for about 4 billion years, but complex organisms like animals didn’t appear until about 600 million years ago, which is not long after the modern episode of plate tectonics began,” said Robert Stern of the University of Texas at Dallas. “Plate tectonics really jump-starts the evolution machine, and we think we understand why.”
***
"The geologic record on Earth suggests that plate tectonics accelerated evolution on land through five distinct processes: it increased the supply of nutrients; sped up the oxygenation of both the atmosphere and the ocean; tempered the climate; caused a high turnover rate of habitat formation and destruction; and offered non-catastrophic environmental pressure that forced organisms to adapt.
"The end result of all these environmental pressures: us.
***
"Earth is the only planet in our solar system to feature plate tectonics. Volcanism exists on some other worlds, like Venus, Mars, and Io, but these worlds have a singular solid shell, rather than multiple moving plates. Similarly, ocean worlds like Enceladus and Europa are bound within an icy coating, forbidding any hypothetical life there from transitioning to land.
***
"There are two essential factors proposed in the revised equation: the fraction of habitable exoplanets with large continents and oceans, and the fraction of those that have plate tectonics lasting more than 500 million years.
"This version is much more nuanced than the original Drake equation, which simply took into account the fraction of habitable planets on which intelligent life had developed.
“'In the original formulation, this factor was thought to be nearly 1, or 100% — that is, evolution on all planets with life would march forward and, with enough time, turn into an intelligent civilization,” Stern said. “Our perspective is: That’s not true.”
"Indeed. Their math reduces the percentage of these planets that develop ACCs to just 0.003% at minimum and 0.2% at maximum – a far cry from the original 100%.
***
"The implications of the original Drake equation were that ACCs should be common, and we should see them everywhere. But including plate tectonics in the equation changes the result, and makes it clear that it’s perfectly understandable why we don’t see ET all across the galaxy.
:So intelligent alien life might be rarer than anyone thought. And Earth may be more special than we knew. All thanks to our planet’s fragmented, unruly, and shifting upper crust."
Comment: produced as a reminder of what we know here. The science writer seems to have just discovered plate tectonic importance. It is not surprising to conclude life is rare throughout the universe.
Continental drift: tectonic activity and ice ages
by David Turell , Saturday, March 16, 2019, 20:28 (2080 days ago) @ David Turell
A new study shows how they are related:
https://wattsupwiththat.com/2019/03/15/weird-science-tectonics-in-the-tropics-trigger-e...
"In a study published in Science, the team reports that each of the last three major ice ages were preceded by tropical “arc-continent collisions” — tectonic pileups that occurred near the Earth’s equator, in which oceanic plates rode up over continental plates, exposing tens of thousands of kilometers of oceanic rock to a tropical environment.
"The scientists say that the heat and humidity of the tropics likely triggered a chemical reaction between the rocks and the atmosphere. Specifically, the rocks’ calcium and magnesium reacted with atmospheric carbon dioxide, pulling the gas out of the atmosphere and permanently sequestering it in the form of carbonates such as limestone.
"Over time, the researchers say, this weathering process, occurring over millions of square kilometers, could pull enough carbon dioxide out of the atmosphere to cool temperatures globally and ultimately set off an ice age.
***
"When an oceanic plate pushes up against a continental plate, the collision typically creates a mountain range of newly exposed rock. The fault zone along which the oceanic and continental plates collide is called a “suture.” Today, certain mountain ranges such as the Himalayas contain sutures that have migrated from their original collision points, as continents have shifted over millenia.
"In 2016, Jagoutz and his colleagues retraced the movements of two sutures that today make up the Himalayas. They found that both sutures stemmed from the same tectonic migration. Eighty million years ago, as the supercontinent known as Gondwana moved north, part of the landmass was crushed against Eurasia, exposing a long line of oceanic rock and creating the first suture; 50 million years ago, another collision between the supercontinents created a second suture.
"The team found that both collisions occurred in tropical zones near the equator, and both preceded global atmospheric cooling events by several million years — which is nearly instantaneous on a geologic timescale. After looking into the rates at which exposed oceanic rock, also known as ophiolites, could react with carbon dioxide in the tropics, the researchers concluded that, given their location and magnitude, both sutures could have indeed sequestered enough carbon dioxide to cool the atmosphere and trigger both ice ages.
***
“'We showed that this process can start and end glaciation,” Jagoutz says. “Then we wondered, how often does that work? If our hypothesis is correct, we should find that for every time there’s a cooling event, there are a lot of sutures in the tropics.”
***
"They identified three periods over the last 540 million years in which major sutures, of about 10,000 kilometers in length, were formed in the tropics. Each of these periods coincided with each of three major, well-known ice ages, in the Late Ordovician (455 to 440 million years ago), the Permo-Carboniferous (335 to 280 million years ago), and the Cenozoic (35 million years ago to present day). Importantly, they found there were no ice ages or glaciation events during periods when major suture zones formed outside of the tropics.
"He notes that a major suture zone, spanning about 10,000 kilometers, is still active today in Indonesia, and is possibly responsible for the Earth’s current glacial period and the appearance of extensive ice sheets at the poles."
Comment: continental movements and subduction zone have played active roles in several cycles which have benefited arranging Earth as a life friendly planet. Not a surprising discovery.