Earth.Parts #20 - Continental collisions & mountain-building by orogeny
Vložit
- čas přidán 25. 06. 2024
- What happens when continental crustal plates collide? When ocean crust collides with continental crust the ocean plate will subduct below the continent and be destroyed, forming a subduction-related mountain range and more continental crust. What about continents?
Continents cannot sustainably subduct one below the other, because continents are made of granite and andesite that are less dense than ocean crust or mantle rock. The continents can't be buried. Instead they grind together and pile up thick masses of crust that drive up the highest mountains on Earth.
Collisions of continents raise mountains by regional orogeny - mountain-building - that involves slow but violent folding, faulting and compression of rock over hundreds to thousands of kilometers. The Himalayan mountains of Asia are the direct result of India colliding with Asia starting about 55 million years ago, and include the tallest mountains in the world; Mount Everest and K2.
Orogeny resulting from continental collisions drive rock to high pressures, even at low to moderate geologic temperatures, resulting in forced recrystallization of the rock's minerals into alternate forms, other minerals, comprised of the same material but reconstituted into forms stable under those intense orogenic conditions.
Regional metamorphism, pressure & temperature-related recrystallization of minerals in rock, can produce highly altered, folded and twisted expressions of natural rock that hosts rare or remarkable minerals.
The Alps are another example of collisional orogeny, one that started about 300 million years ago when Africa and Europe collided, and continuing sporadically since then. Epic scenery such as now found in Switzerland at Jungfraujoch, or the Matterhorn which is comprised of rock from two continents.
The Appalachian mountains of eastern North America are eroded remains of a long history of orogeny, beginning about 450 million years ago when an ancient subduction-related volcanic island chain collided with proto-North America, raising a vast range of mountains, the Taconic orogeny.
Then, around 375 million years ago an island continent we now call Avalonia collided with the Taconic mountain coast, raising up a more northerly range of peaks, the Acadian mountains. Then around 300 million years ago Africa and proto-North America collided, raising the Appalachian mountains during what is called the Alleghenian orogeny around 250 million years ago.
Around 180 million years ago Africa split from North America, and erosion since then has worn down the ancient Taconic, Acadian and Alleghenian ranges to form the gentler slopes of the modern Appalachians. Today the highest Appalachian peak, Mt. Mitchell, may not look like Mt. Everest, but long ago it and its sibling heights were perhaps even higher still.
Great video! I live in the current taconic mountains on the Rensselaer Plateau which has the oldest rocks in NYS. The northern Taconic’s are still quite impressive! The highest summit being Equinox Mountain in Manchester Vermont at just under 4k feet in elevation.
Really enjoyable video - a complex topic, explained clearly, is always more likely to be understood.
Nicely done! I didn’t know that the Appalachians are actually three separate ranges formed at different times.
Excellent! Great explanation, very high quality stuff. Thanks.
Impressive video. Clear and comprehensive. thanks
Straightforward, well explained. So much to learn. Thank you.
you actually make rocks interesting
Great vid. Well done. Thanks. I just Subscribed. Looks like I have some catching up to do.
Excellent explanation. I've been reading in this area and your video graphics and explanations were outstandingly helpful to solidify what I've learned. Thank you.
thanks for your vids. Really appreciate them
A fantastic explanation. So interesting.
OMG I love this, this helps so much! I thank you! ❤️
I live on the Canadian part of the Northern Appalachians. Thanks for helping me understand how they formed.
Remember also that the Appalachians extend into The British Isles and Scandinavia as Northern Europe was also part of the story. The Northwest corner of Scotland is part of The Canadian Shield up to 3 billion years old. There are also sedimentray sandstones over a billion years old.
Excellent presentation, and so well explained. Very helpful. Thank you.
Great video. Really enjoyed the Appalachian orogenies as I am currently conducting a detrital zircon geochronology study in the Midcontinent and it is theorized that sediments came from the northern Appalachians via large transcontinental fluvial systems.
Nice sigma clasts in the metamorphic rock example you showed.
Concerning the Lord of the Rings references: 9:24 The valley next to Jungfraujoch is where J R R Tolkien was inspired for Rivendell and Moria when he went there 1911. en.wikipedia.org/wiki/Lauterbrunnen
I guess eventually a new subduction break will appear going under southern India.
Fantastic, thank you
thank you!
thanks! i just realised volcanic arcs collide too
11:20 Appalachian mountain
I was watching a CZcams video a few days ago that claimed that the Himalayan Range was a result of a near Earth object impact. A “grazing” of body against Earth and it left the telltale flattening impact that is the Himalayan Range.
The red crystal at 8:01, I have found 4 different ones like that but 3 where white and one was like a brownish/red. I'm in the mountains of north carolina
Hello sir! I am from India and here in its geological map on the Northern side Metamorphic rock is shown.. And as per your explanation there should be metamorphic rock
At the time Pangea separated I’ve seen suggestions of a hot spot at the point of contact with North America, Africa and Europe.
I was wondering if there’s any evidence of this within the Appalachian Mountain Range that you’re aware of?
Thanks for the question & for watching! Hot spot activity is often associated with continental break-ups. The break-up of Pangaea and the formation of the Atlantic ocean were likely driven by heat buildup beneath the converged mass of the super-continent, and the effects of some of that hot spot activity can be tracked through geologic time afterward. There's a good paper by Golonka and Bocharova (2000) that covers some of that geology. You can read that one for free at:
www.researchgate.net/publication/222000391_Hot_spot_activity_and_the_break-up_of_Pangea
Interesting, well done video explanation. Imagine this happening over the course of tens or hundreds of years.😮
The Appalachian Chain in Alabama linked up with the Ouachita -Marathon Mountain Range that snaked across Mississippi, Arkansas, Oklahoma and Texas. Those were created when the South American plate collided with the North American plate and separated along the line of that range. They believe that the NA plate traveled over the Bermuda Hot Spot which made the Ouachita Mountains rise in elevation in Arkansas and Mississippi. Those eroded away then dropped in elevation as it moved away from the hot spot to create the Mississippi Ebayment that was filled by water from the Gulf of Mexico. I think some believe the failed Reelfoot Rift (New Madrid fault system) was created when the hot spot moved away. There's another failed rift in SE Oklahoma that's below where a mountain range was attached to the Ouachita Mountains at a right angle.
K2 is not in Pakistan infact it is located in Pakistan Occupied Kashmir.
Here from Earth Science EGCC G111