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I don't understand how land masses the size of africa detaches. The map shows africa attached to the US, but this doesn't make sense. I can understand water lev

I don't understand how land masses the size of africa detaches. The map shows africa attached to the US, but this doesn't make sense. I can understand water levels changing, exposing new areas that might have been underwater, drying up and turning into land masses, as well as areas that were previously land, becoming filled with water.

danielbln 6y ago
All continents rest on tectonic plates, which kind of rest on the liquid core and are moving around on it. Let enough time pass, and the plates will move around, and the continents with them. Check out this image of the plates: https://en.wikipedia.org/wiki/Plate_tectonics#/media/File:Plates_tect2_en.svg https://en.wikipedia.org/wiki/Plate_tectonics#/media/File:Pl...
Waterluvian 6y ago
It’s a fantastic question this stuff isn’t intuitive. http://mapdesign.icaci.org/wp-content/uploads/2012/04/atlantic_lg.jpg http://mapdesign.icaci.org/wp-content/uploads/2012/04/atlant... Consider this model: the Earth is like a puzzle. Its crust is made up of a bunch of pieces that all fit together. But those pieces aren’t unchanging. They all sit on top of a huge soft sludgey core called the mantle. And they want to slowly (slooooooowly) slide around. At each boundary between pieces one of three things can happen: - they slide against each other - they diverge from each other - they press into each other, often one going under the other, sometimes one pushing the other. A continent can move, oh so slowly, over millions of years through a combination of shifting along with other plates, or having one side of its plate grow (move away and have the new gap filled with the molten plasticy goo underneath), while the other side pushes away a plate or disappears underneath the other plate. The map I linked shows a massive stretch mark of the Earth in the Atlantic Ocean. This is one striking piece of evidence that the above effects have been happening over a long long time. It’s basically the boundary between a few plates. And it shows all this brand new ocean floor that came flowing up from under the crust (then cooled and got hard) when a gap was created because they separated apart.
- laumars 6y ago
  Good explanation. To expand on that, earthquakes and volcanoes are the result of those plates colliding and separating.
- tekcyb-org 6y ago
  Wow thank you for the explanation and that picture you provided makes it very clear as well. I did not realize that the world was divided into plates.
  - tremon 6y ago
    There's a BBC documentary on this that's now around 25 years old, called Earth Story (https://en.wikipedia.org/wiki/Earth_Story https://en.wikipedia.org/wiki/Earth_Story). It describes not only what we know, but how we know it. As documentaries go, it's rather in-depth but easily digestible.
    - Wubdidu 6y ago
      Thanks for the suggestion, it sounds really interesting based on some YouTube comments. Just ordered it used from the UK, first time I'll be watching an actual DVD since... years. I think I do have a DVD drive somewhere in storage.
- EdwardDiego 6y ago
  Looking at New Zealand 35 million and 20 million years ago on that globe (search for one of our cities like Auckland or Christchurch) is really illuminating when compared to its current shape, most of the South Island is to the west of the North Island, as the plate boundary between the Indian and Pacific plate runs through the South Island, and the eastern side has been moving south-west for millennia to form the current shape of the land, and our Southern Alps.
- titzer 6y ago
  Another thing to keep in mind: these tectonic plates are heavy. Like unimaginably heavy. They can be thousands of miles wide and tens of miles thick and are as dense as rock. They exert huge pressure on that soft sludgey core, which is incidentally being heated by a low-level nuclear furnace in the center of the Earth. So the plates are more like a lid on a boiling pot that is foaming over. They're all getting jostled by insanely powerful pressure from underneath. Every once in a while a pimple appears and goes kaboom.
Rexxar 6y ago
It's tectonic plates (https://en.wikipedia.org/wiki/Plate_tectonics https://en.wikipedia.org/wiki/Plate_tectonics). You can currently see continent splitting in Island and in Africa : https://en.wikipedia.org/wiki/East_African_Rift https://en.wikipedia.org/wiki/East_African_Rift
phkahler 6y ago
To understand the separation of the Americas from African you may want to read about the mid ocean ridge: https://en.m.wikipedia.org/wiki/Mid-ocean_ridge https://en.m.wikipedia.org/wiki/Mid-ocean_ridge Now how that large land mass came to be is an interesting question to me. The globe shown here in the title/link is clearly not homogeneous. The land mass on one side must be less dense than the rest of the earth for it to protrude above sea level that way.
- spionnaidh 6y ago
  The continents are indeed less dense than the oceans! On average, the continental crust has a composition that is also seen in magmas that are produced at subduction zones (where denser oceanic crust is forced under continental crust) by the melting of the mantle. At the mid-ocean ridges, water is circulated through the newly produced oceanic crust, and the fresh basalt is metamorphosed, causing new minerals to grow which contain water as a part of their structure. Up to a few hundred million years later, this oceanic crust reaches a subduction zone, where it is pulled into the mantle. As it sinks, it is exposed to higher pressures and the water-bearing minerals become unstable. The water within them is driven off the crust and rises into the overlying mantle. At these pressures and temperatures, water is to rock what salt is to ice, and part of the mantle melts - think of it as a kind of 'slush'. As the magma (the liquid part of this slush) rises to the surface, it begins to crystallise, and the denser crystals (which form first) sink. Overall, this makes the magma less dense, continuing to drive it to the surface, where it may either eventually stall in the crust (in a pluton) or be erupted in a volcano. Now there is less dense material sitting on top of and within the oceanic crust and an island arc is born - an example today is the Aleutian Islands. The magmas formed at subduction zones have a distinctive geochemical signature called the 'calc-alkaline' trend. Whereas magmas at mid-ocean ridges become enriched in iron because of the crystallisation of plagioclase feldspar, at subduction zones the presence of water suppresses feldspar crystallisation, instead producing 'wet' minerals like amphibole. As a result, these magmas do not become enriched in iron as they rise through the crust, and instead become rich in sodium and potassium. These magmas also have distinctive radiogenic isotope ratios and trace element contents. The continental crust (while highly compositionally varied) on average has similar signatures, suggesting that it was formed by this kind of activity. The fun happens when two of these island arcs collide. They are both less dense than the underlying mantle, so neither will subduct easily. Instead, they coalesce into a single mass, and a continent is born. More common today is the collision of an island arc with a pre-existing continent. This happened before India collided with Asia to form the Himalayas, and the calc-alkaline plutonic rocks are visible at the surface in Tibet today. This is how the continents grow. The continents are thought to have started to form during the Archaen Eon, starting at four billion years ago. The rate at which they formed is still very much up for debate, but it is thought that crustal growth was more rapid back then as compared to today, and was mostly complete by around 2.5 billion years ago. Today's tectonic plates are cored by ancient cratons, the oldest and most tectonically stable pieces of crust. Around these cratons are progressively younger strips of crust stuck on by colliding island arcs. Much of North America is made up of island arcs stuck to the Laurentian craton.

danielbln 6y ago

All continents rest on tectonic plates, which kind of rest on the liquid core and are moving around on it. Let enough time pass, and the plates will move around, and the continents with them. Check out this image of the plates: https://en.wikipedia.org/wiki/Plate_tectonics#/media/File:Plates_tect2_en.svg https://en.wikipedia.org/wiki/Plate_tectonics#/media/File:Pl...

Waterluvian 6y ago

It’s a fantastic question this stuff isn’t intuitive. http://mapdesign.icaci.org/wp-content/uploads/2012/04/atlantic_lg.jpg http://mapdesign.icaci.org/wp-content/uploads/2012/04/atlant... Consider this model: the Earth is like a puzzle. Its crust is made up of a bunch of pieces that all fit together. But those pieces aren’t unchanging. They all sit on top of a huge soft sludgey core called the mantle. And they want to slowly (slooooooowly) slide around. At each boundary between pieces one of three things can happen: - they slide against each other - they diverge from each other - they press into each other, often one going under the other, sometimes one pushing the other. A continent can move, oh so slowly, over millions of years through a combination of shifting along with other plates, or having one side of its plate grow (move away and have the new gap filled with the molten plasticy goo underneath), while the other side pushes away a plate or disappears underneath the other plate. The map I linked shows a massive stretch mark of the Earth in the Atlantic Ocean. This is one striking piece of evidence that the above effects have been happening over a long long time. It’s basically the boundary between a few plates. And it shows all this brand new ocean floor that came flowing up from under the crust (then cooled and got hard) when a gap was created because they separated apart.

laumars 6y ago
Good explanation. To expand on that, earthquakes and volcanoes are the result of those plates colliding and separating.
tekcyb-org 6y ago
Wow thank you for the explanation and that picture you provided makes it very clear as well. I did not realize that the world was divided into plates.
- tremon 6y ago
  There's a BBC documentary on this that's now around 25 years old, called Earth Story (https://en.wikipedia.org/wiki/Earth_Story https://en.wikipedia.org/wiki/Earth_Story). It describes not only what we know, but how we know it. As documentaries go, it's rather in-depth but easily digestible.
  - Wubdidu 6y ago
    Thanks for the suggestion, it sounds really interesting based on some YouTube comments. Just ordered it used from the UK, first time I'll be watching an actual DVD since... years. I think I do have a DVD drive somewhere in storage.
EdwardDiego 6y ago
Looking at New Zealand 35 million and 20 million years ago on that globe (search for one of our cities like Auckland or Christchurch) is really illuminating when compared to its current shape, most of the South Island is to the west of the North Island, as the plate boundary between the Indian and Pacific plate runs through the South Island, and the eastern side has been moving south-west for millennia to form the current shape of the land, and our Southern Alps.
titzer 6y ago
Another thing to keep in mind: these tectonic plates are heavy. Like unimaginably heavy. They can be thousands of miles wide and tens of miles thick and are as dense as rock. They exert huge pressure on that soft sludgey core, which is incidentally being heated by a low-level nuclear furnace in the center of the Earth. So the plates are more like a lid on a boiling pot that is foaming over. They're all getting jostled by insanely powerful pressure from underneath. Every once in a while a pimple appears and goes kaboom.

Rexxar 6y ago

It's tectonic plates (https://en.wikipedia.org/wiki/Plate_tectonics https://en.wikipedia.org/wiki/Plate_tectonics). You can currently see continent splitting in Island and in Africa : https://en.wikipedia.org/wiki/East_African_Rift https://en.wikipedia.org/wiki/East_African_Rift

phkahler 6y ago

To understand the separation of the Americas from African you may want to read about the mid ocean ridge: https://en.m.wikipedia.org/wiki/Mid-ocean_ridge https://en.m.wikipedia.org/wiki/Mid-ocean_ridge Now how that large land mass came to be is an interesting question to me. The globe shown here in the title/link is clearly not homogeneous. The land mass on one side must be less dense than the rest of the earth for it to protrude above sea level that way.

spionnaidh 6y ago
The continents are indeed less dense than the oceans! On average, the continental crust has a composition that is also seen in magmas that are produced at subduction zones (where denser oceanic crust is forced under continental crust) by the melting of the mantle. At the mid-ocean ridges, water is circulated through the newly produced oceanic crust, and the fresh basalt is metamorphosed, causing new minerals to grow which contain water as a part of their structure. Up to a few hundred million years later, this oceanic crust reaches a subduction zone, where it is pulled into the mantle. As it sinks, it is exposed to higher pressures and the water-bearing minerals become unstable. The water within them is driven off the crust and rises into the overlying mantle. At these pressures and temperatures, water is to rock what salt is to ice, and part of the mantle melts - think of it as a kind of 'slush'. As the magma (the liquid part of this slush) rises to the surface, it begins to crystallise, and the denser crystals (which form first) sink. Overall, this makes the magma less dense, continuing to drive it to the surface, where it may either eventually stall in the crust (in a pluton) or be erupted in a volcano. Now there is less dense material sitting on top of and within the oceanic crust and an island arc is born - an example today is the Aleutian Islands. The magmas formed at subduction zones have a distinctive geochemical signature called the 'calc-alkaline' trend. Whereas magmas at mid-ocean ridges become enriched in iron because of the crystallisation of plagioclase feldspar, at subduction zones the presence of water suppresses feldspar crystallisation, instead producing 'wet' minerals like amphibole. As a result, these magmas do not become enriched in iron as they rise through the crust, and instead become rich in sodium and potassium. These magmas also have distinctive radiogenic isotope ratios and trace element contents. The continental crust (while highly compositionally varied) on average has similar signatures, suggesting that it was formed by this kind of activity. The fun happens when two of these island arcs collide. They are both less dense than the underlying mantle, so neither will subduct easily. Instead, they coalesce into a single mass, and a continent is born. More common today is the collision of an island arc with a pre-existing continent. This happened before India collided with Asia to form the Himalayas, and the calc-alkaline plutonic rocks are visible at the surface in Tibet today. This is how the continents grow. The continents are thought to have started to form during the Archaen Eon, starting at four billion years ago. The rate at which they formed is still very much up for debate, but it is thought that crustal growth was more rapid back then as compared to today, and was mostly complete by around 2.5 billion years ago. Today's tectonic plates are cored by ancient cratons, the oldest and most tectonically stable pieces of crust. Around these cratons are progressively younger strips of crust stuck on by colliding island arcs. Much of North America is made up of island arcs stuck to the Laurentian craton.