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We’re Wrong About How Mountains Form
YouTube: | https://youtube.com/watch?v=TxOYM4q-irQ |
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Likes: | 10,708 |
Comments: | 372 |
Duration: | 06:28 |
Uploaded: | 2023-09-13 |
Last sync: | 2024-12-07 20:30 |
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Citation formatting is not guaranteed to be accurate. | |
MLA Full: | "We’re Wrong About How Mountains Form." YouTube, uploaded by SciShow, 13 September 2023, www.youtube.com/watch?v=TxOYM4q-irQ. |
MLA Inline: | (SciShow, 2023) |
APA Full: | SciShow. (2023, September 13). We’re Wrong About How Mountains Form [Video]. YouTube. https://youtube.com/watch?v=TxOYM4q-irQ |
APA Inline: | (SciShow, 2023) |
Chicago Full: |
SciShow, "We’re Wrong About How Mountains Form.", September 13, 2023, YouTube, 06:28, https://youtube.com/watch?v=TxOYM4q-irQ. |
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We think we know how mountains form. Plate tectonics causes rock to be pushed up at fault boundaries. Except that model is hard to prove, and a new study suggests it might actually be a lot more complicated.
Hosted by: Stefan Chin
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Support SciShow by becoming a patron on Patreon: https://www.patreon.com/scishow
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Huge thanks go to the following Patreon supporters for helping us keep SciShow free for everyone forever: Adam Brainard, Alex Hackman, Ash, Bryan Cloer, charles george, Chris Mackey, Chris Peters, Christoph Schwanke, Christopher R Boucher, Dr. Melvin Sanicas, Harrison Mills, Jaap Westera, Jason A Saslow, Jeffrey Mckishen, Jeremy Mattern, Kevin Bealer, Matt Curls, Michelle Dove, Piya Shedden, Rizwan Kassim, Sam Lutfi
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Sources:
https://www.nature.com/articles/s41561-023-01185-4
https://www.nature.com/articles/s41561-023-01192-5
https://www.sciencedaily.com/releases/2023/06/230602115057.htm
http://academic.brooklyn.cuny.edu/geology/grocha/plates/platetec21.htm
https://education.nationalgeographic.org/resource/mantle/
https://www.nature.com/articles/s41586-021-04157-z
https://www.theguardian.com/science/2016/nov/06/geology-italy-earthquakes-apennines-tectonic-plates-norcia-terrawatch
https://www.britannica.com/science/tectonic-landform
https://www.soest.hawaii.edu/GG/ASK/mountains.html
https://www.bbc.co.uk/bitesize/guides/zss8rwx/revision/3
https://manoa.hawaii.edu/exploringourfluidearth/physical/ocean-floor/continental-movement-plate-tectonics
https://www.earthquakeauthority.com/Blog/2020/Understanding-Plate-Tectonic-Theory
We think we know how mountains form. Plate tectonics causes rock to be pushed up at fault boundaries. Except that model is hard to prove, and a new study suggests it might actually be a lot more complicated.
Hosted by: Stefan Chin
----------
Support SciShow by becoming a patron on Patreon: https://www.patreon.com/scishow
----------
Huge thanks go to the following Patreon supporters for helping us keep SciShow free for everyone forever: Adam Brainard, Alex Hackman, Ash, Bryan Cloer, charles george, Chris Mackey, Chris Peters, Christoph Schwanke, Christopher R Boucher, Dr. Melvin Sanicas, Harrison Mills, Jaap Westera, Jason A Saslow, Jeffrey Mckishen, Jeremy Mattern, Kevin Bealer, Matt Curls, Michelle Dove, Piya Shedden, Rizwan Kassim, Sam Lutfi
----------
Looking for SciShow elsewhere on the internet?
SciShow Tangents Podcast: https://scishow-tangents.simplecast.com/
TikTok: https://www.tiktok.com/@scishow
Twitter: http://www.twitter.com/scishow
Instagram: http://instagram.com/thescishow
Facebook: http://www.facebook.com/scishow
#SciShow #science #education #learning #complexly
----------
Sources:
https://www.nature.com/articles/s41561-023-01185-4
https://www.nature.com/articles/s41561-023-01192-5
https://www.sciencedaily.com/releases/2023/06/230602115057.htm
http://academic.brooklyn.cuny.edu/geology/grocha/plates/platetec21.htm
https://education.nationalgeographic.org/resource/mantle/
https://www.nature.com/articles/s41586-021-04157-z
https://www.theguardian.com/science/2016/nov/06/geology-italy-earthquakes-apennines-tectonic-plates-norcia-terrawatch
https://www.britannica.com/science/tectonic-landform
https://www.soest.hawaii.edu/GG/ASK/mountains.html
https://www.bbc.co.uk/bitesize/guides/zss8rwx/revision/3
https://manoa.hawaii.edu/exploringourfluidearth/physical/ocean-floor/continental-movement-plate-tectonics
https://www.earthquakeauthority.com/Blog/2020/Understanding-Plate-Tectonic-Theory
Thank you to Endel for supporting this SciShow video.
Endel is an app that creates personalized soundscapes to help you focus, relax, and sleep. The first 100 people to click our description link down below will get a one week free trial.
Funny thing about science. Sooner or later, you have to provide some evidence that whatever you’re going on about is actually true. Take plate tectonics.
We’ve gotten pretty good at using this model to explain how the movement of Earth’s plates can create things like mountains on the surface. Except, it’s hard to test whether we’re actually right, because plate tectonics happens really, really slowly. But a study in the Calabrian mountains of Italy has come up with some of that “evidence” stuff and revealed that things might not always be as simple as we imagine them to be.
We might be totally wrong about how mountains form. [intro] Plate tectonics is powered largely by forces we cannot see. A few dozen kilometers below the surface, the Earth’s mantle flows in huge convection currents, a bit like a pan of boiling water. It’s heated from the planet’s deep interior, which makes plumes of warm material rise up towards the surface, before spreading out, cooling, and sinking back to start the cycle again.
And on the surface, cold and rigid tectonic plates making up the crust are pushed and pulled around like floaty toys on a pool. Not that your pool is ever filled with boiling water, I hope, but… you get the picture. When the tectonic plates meet or diverge, they form dramatic landscapes like rift valleys, volcanoes, and mountain chains.
It’s kind of intuitive that mountains are built when plates collide. Picture the leading edge of a mountain range, forming where one plate is subducting beneath another one. The top layers of sedimentary rocks are scraped off and pile up, a bit like the ice scraped off your windshield.
And all that thickened crust acts like an iceberg made of rock, floating on the fluid mantle underneath. If all that’s true, the faster the plates collide and thicken the crust, the faster the mountains will rise up. So if we could measure mountain-building speed and compare it to how fast plates collide, we could test that model.
The problem is, most tectonic plates move at about the same speed as your fingernails grow, and mountains take millions of years to pile up. So it’s incredibly hard to actually test our assumptions. It’s not like we can sit in front of them with a stopwatch to compare their growth with the rate of collision.
However, in a paper published in Nature Geoscience in June 2023, scientists have come up with an innovative new way of reconstructing past rates of growth, by reading the landscape itself. The study is focused on the ‘toe’ of southern Italy, where the Calabrian mountains have been formed by the African plate crashing northwards into the Eurasian plate. Researchers from the US have combined several different geological approaches to interpret the shape and geology of the landscape.
They used ratios of radioactive elements in the rocks to work out their ages, and then interpreted the physical shapes and features of the mountain rocks to figure out where they were when they formed. Together, this helped them piece together the speed of subduction as well as the timing and speed of mountain building over the last 30 million years. For example, flatter parts of the mountain terrain were formed when rock uplift was slow, whereas steeper sections suggest faster rates of uplift.
And the traces of rivers cutting down through existing rocks show when elevations changed quickly as well. Ultimately, these different lines of evidence showed that the Calabrian mountain building wasn’t consistent over time, but was more stop-start. And surprisingly, the rates of uplift were not consistent with the rate of subduction of the African plate.
When subduction was fast, uplift was slow, and when subduction rates slowed, the uplift was fast. This is the opposite of what we’d expect from our simple models of tectonic crustal thickening. The results suggest that in this case at least, mountain building is more than skin deep, and the researchers have had to find another theory for how the Calabrian mountains were uplifted.
Remember those convection currents? Their idea is that the part of the African plate that has been subducted underneath Eurasia actively affects how the mantle underneath convects, and that this in turn affects the elevation of the crust. It’s known as dynamic topography, and it’s something that’s been suggested in computer models, but never before seen in nature.
It works like this. As the African plate descends, it drags some of the mantle down with it, and this downward flow is enough to trigger a new convection current to form in the upper mantle. Mantle material flows down next to the subducting slab, and is heated and returns to the surface some distance away.
But this vigorous downwelling of the mantle near to the subduction zone effectively sucks the whole of the crust downwards in this region, and it’s enough to counteract and cancel out any uplift that happens due to crustal thickening. So subduction is fast, but uplift is slow. This situation doesn’t go on forever, though.
Eventually the slab of crust hits a transition zone in the mantle, at about 660 kilometers deep. Below this, the lower mantle is much denser, and the swallowed crust just kind of sits on top of it. Subduction slows, and eventually the slab disintegrates and tears off, which disrupts that vigorous convection and downwelling.
Without the suction from the mantle and the weight of the slab, the crust can bounce back up. Uplift is now fast, even though subduction and actual crustal thickening have slowed. So while the basic idea isn’t going anywhere, it seems there’s more to this plate tectonic story than we first thought.
The crustal plates aren’t just pushed around on top of a churning mantle, but have the ability to change what’s going on underneath as well. And this in turn ends up changing how and when the features on the surface are built. There’s more work to do to find out if this process is unique to these mountains, or happens all around the world.
And the authors hope that their new approach will help reconstruct mountain-building elsewhere. But this study shows us that the Earth is a more complicated interdynamic system than we previously imagined, in which those rocky pool floaties can change the conditions in the pool itself. And better understanding how and why mountains have grown helps us to more accurately piece together our planet’s history, and with it the history of… just about everything.
This SciShow video is supported by Endel. Endel takes what we know about sound and combines it with AI-powered technology in an app that helps you focus, relax, and sleep. That technology adapts in real-time to personal inputs like location, weather, circadian rhythm, and heart rate to help you concentrate for longer periods of time when studying or working.
And they do it through simple, pleasant sounds. To direct your focus toward the Endel app, you can click the link down below in the description. The first 100 people to download Endel using that link will get a free week of audio.
Thank you to Endel app for supporting this SciShow video and thank you for watching. [ outro ]
Endel is an app that creates personalized soundscapes to help you focus, relax, and sleep. The first 100 people to click our description link down below will get a one week free trial.
Funny thing about science. Sooner or later, you have to provide some evidence that whatever you’re going on about is actually true. Take plate tectonics.
We’ve gotten pretty good at using this model to explain how the movement of Earth’s plates can create things like mountains on the surface. Except, it’s hard to test whether we’re actually right, because plate tectonics happens really, really slowly. But a study in the Calabrian mountains of Italy has come up with some of that “evidence” stuff and revealed that things might not always be as simple as we imagine them to be.
We might be totally wrong about how mountains form. [intro] Plate tectonics is powered largely by forces we cannot see. A few dozen kilometers below the surface, the Earth’s mantle flows in huge convection currents, a bit like a pan of boiling water. It’s heated from the planet’s deep interior, which makes plumes of warm material rise up towards the surface, before spreading out, cooling, and sinking back to start the cycle again.
And on the surface, cold and rigid tectonic plates making up the crust are pushed and pulled around like floaty toys on a pool. Not that your pool is ever filled with boiling water, I hope, but… you get the picture. When the tectonic plates meet or diverge, they form dramatic landscapes like rift valleys, volcanoes, and mountain chains.
It’s kind of intuitive that mountains are built when plates collide. Picture the leading edge of a mountain range, forming where one plate is subducting beneath another one. The top layers of sedimentary rocks are scraped off and pile up, a bit like the ice scraped off your windshield.
And all that thickened crust acts like an iceberg made of rock, floating on the fluid mantle underneath. If all that’s true, the faster the plates collide and thicken the crust, the faster the mountains will rise up. So if we could measure mountain-building speed and compare it to how fast plates collide, we could test that model.
The problem is, most tectonic plates move at about the same speed as your fingernails grow, and mountains take millions of years to pile up. So it’s incredibly hard to actually test our assumptions. It’s not like we can sit in front of them with a stopwatch to compare their growth with the rate of collision.
However, in a paper published in Nature Geoscience in June 2023, scientists have come up with an innovative new way of reconstructing past rates of growth, by reading the landscape itself. The study is focused on the ‘toe’ of southern Italy, where the Calabrian mountains have been formed by the African plate crashing northwards into the Eurasian plate. Researchers from the US have combined several different geological approaches to interpret the shape and geology of the landscape.
They used ratios of radioactive elements in the rocks to work out their ages, and then interpreted the physical shapes and features of the mountain rocks to figure out where they were when they formed. Together, this helped them piece together the speed of subduction as well as the timing and speed of mountain building over the last 30 million years. For example, flatter parts of the mountain terrain were formed when rock uplift was slow, whereas steeper sections suggest faster rates of uplift.
And the traces of rivers cutting down through existing rocks show when elevations changed quickly as well. Ultimately, these different lines of evidence showed that the Calabrian mountain building wasn’t consistent over time, but was more stop-start. And surprisingly, the rates of uplift were not consistent with the rate of subduction of the African plate.
When subduction was fast, uplift was slow, and when subduction rates slowed, the uplift was fast. This is the opposite of what we’d expect from our simple models of tectonic crustal thickening. The results suggest that in this case at least, mountain building is more than skin deep, and the researchers have had to find another theory for how the Calabrian mountains were uplifted.
Remember those convection currents? Their idea is that the part of the African plate that has been subducted underneath Eurasia actively affects how the mantle underneath convects, and that this in turn affects the elevation of the crust. It’s known as dynamic topography, and it’s something that’s been suggested in computer models, but never before seen in nature.
It works like this. As the African plate descends, it drags some of the mantle down with it, and this downward flow is enough to trigger a new convection current to form in the upper mantle. Mantle material flows down next to the subducting slab, and is heated and returns to the surface some distance away.
But this vigorous downwelling of the mantle near to the subduction zone effectively sucks the whole of the crust downwards in this region, and it’s enough to counteract and cancel out any uplift that happens due to crustal thickening. So subduction is fast, but uplift is slow. This situation doesn’t go on forever, though.
Eventually the slab of crust hits a transition zone in the mantle, at about 660 kilometers deep. Below this, the lower mantle is much denser, and the swallowed crust just kind of sits on top of it. Subduction slows, and eventually the slab disintegrates and tears off, which disrupts that vigorous convection and downwelling.
Without the suction from the mantle and the weight of the slab, the crust can bounce back up. Uplift is now fast, even though subduction and actual crustal thickening have slowed. So while the basic idea isn’t going anywhere, it seems there’s more to this plate tectonic story than we first thought.
The crustal plates aren’t just pushed around on top of a churning mantle, but have the ability to change what’s going on underneath as well. And this in turn ends up changing how and when the features on the surface are built. There’s more work to do to find out if this process is unique to these mountains, or happens all around the world.
And the authors hope that their new approach will help reconstruct mountain-building elsewhere. But this study shows us that the Earth is a more complicated interdynamic system than we previously imagined, in which those rocky pool floaties can change the conditions in the pool itself. And better understanding how and why mountains have grown helps us to more accurately piece together our planet’s history, and with it the history of… just about everything.
This SciShow video is supported by Endel. Endel takes what we know about sound and combines it with AI-powered technology in an app that helps you focus, relax, and sleep. That technology adapts in real-time to personal inputs like location, weather, circadian rhythm, and heart rate to help you concentrate for longer periods of time when studying or working.
And they do it through simple, pleasant sounds. To direct your focus toward the Endel app, you can click the link down below in the description. The first 100 people to download Endel using that link will get a free week of audio.
Thank you to Endel app for supporting this SciShow video and thank you for watching. [ outro ]