Tetonic Plates
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Tetonic Plates
by Old Timer Tue Mar 24, 2009 3:03 pm
Tetonic Plates
Where the different plates meet, they typically interact in one of four ways:
If the two plates are moving away from each other, an ocean ridge or continental ridge forms, depending on whether the plates meet under the ocean or on land. As the two plates separate, the mantle rock from the asthenosphere layer below flows up into the void between the plates. Because the pressure is not as great at this level, the mantle rock will melt, forming magma. As the magma flows out, it cools, hardening to form new crust. This fills in the gap created by the plates diverging. This sort of magma production is called spreading center volcanism.
At the point where two plates collide, one plate may be pushed under the other plate, so that it sinks into the mantle. This process, called subduction, typically forms a trench, a very deep ditch, usually in the ocean floor. As the rigid lithosphere pushes down into the hot, high-pressure mantle, it heats up. Many scientists believe that the sinking lithosphere layer can't melt at this depth, but that the heat and pressure forces the water (the surface water and water from hydrated minerals) out of the plate and into the mantle layer above. The increased water content lowers the melting point of the mantle rock in this wedge, causing it to melt into magma. This sort of magma production is called subduction zone volcanism.
If the plates collide and neither plate can subduct under the other, the crust material will just "crumple," pushing up mountains. This process does not produce volcanoes. This kind of boundary can develop later into a subduction zone.
Some plates move against each other rather than push or pull apart. These transform plate boundaries rarely produce volcanic activity.
The Pangaea Theory
The Pangaea theory is one that states that all present continents were once together and collectively known as a 'supercontinent' called a Pangaea. The word 'Pangaea' means 'all lands' in Greek, accurately defining the way the continents were 200 millions years ago before it split up. These split-up pieces drifted slowly apart and became the way they are today. Even until now, the shape of the Earth surface is still changing, and it will be forever, as long as the mantle underneath the Earth's crust gets heated and convection currents in the magma keeps dragging the plates.
The Pangaea theory was treated with much skepticsm when it was first raised. But since then, there have been much evidence to support this theory.
Where the different plates meet, they typically interact in one of four ways:
If the two plates are moving away from each other, an ocean ridge or continental ridge forms, depending on whether the plates meet under the ocean or on land. As the two plates separate, the mantle rock from the asthenosphere layer below flows up into the void between the plates. Because the pressure is not as great at this level, the mantle rock will melt, forming magma. As the magma flows out, it cools, hardening to form new crust. This fills in the gap created by the plates diverging. This sort of magma production is called spreading center volcanism.
At the point where two plates collide, one plate may be pushed under the other plate, so that it sinks into the mantle. This process, called subduction, typically forms a trench, a very deep ditch, usually in the ocean floor. As the rigid lithosphere pushes down into the hot, high-pressure mantle, it heats up. Many scientists believe that the sinking lithosphere layer can't melt at this depth, but that the heat and pressure forces the water (the surface water and water from hydrated minerals) out of the plate and into the mantle layer above. The increased water content lowers the melting point of the mantle rock in this wedge, causing it to melt into magma. This sort of magma production is called subduction zone volcanism.
If the plates collide and neither plate can subduct under the other, the crust material will just "crumple," pushing up mountains. This process does not produce volcanoes. This kind of boundary can develop later into a subduction zone.
Some plates move against each other rather than push or pull apart. These transform plate boundaries rarely produce volcanic activity.
The Pangaea Theory
The Pangaea theory is one that states that all present continents were once together and collectively known as a 'supercontinent' called a Pangaea. The word 'Pangaea' means 'all lands' in Greek, accurately defining the way the continents were 200 millions years ago before it split up. These split-up pieces drifted slowly apart and became the way they are today. Even until now, the shape of the Earth surface is still changing, and it will be forever, as long as the mantle underneath the Earth's crust gets heated and convection currents in the magma keeps dragging the plates.
The Pangaea theory was treated with much skepticsm when it was first raised. But since then, there have been much evidence to support this theory.
Old Timer-
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Registration date : 2009-01-13
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