Explanation of divergent plate boundaries and shield volcano's

Now that you know what plate tectonics is and what the structure of the earth is, we can look at the movement of the plates. Divergent zones are explained in this video. These are zones where the plates move apart.

As you have seen in the previous video, the continental crust is much thicker than the oceanic crust. Under a continental crust, the mantle can therefore become very hot, because the mantle cannot lose the heat. The rock expands due to the heat. If the heat makes the rock fluid, it can expand even more.

The expanding magma causes the continent to rise. The continent can therefore break, due to the pressure. Gravity then ensures that the broken plate will slip. This force is called ridge push. This is one of the reasons that plates move.

A very long crack appears in the crust where the plates move apart. Here material can rise from the mantle and solidify on the surface as basalt. This new crust is deeper than the previous continental crust. As a result, water flows to this low point. If the plates keep moving apart and more oceanic crust is created, an ocean can form.
The crack where oceanic crust is made sometimes lies exactly between 2 continental plates, and therefore in the middle of the ocean. Here the ocean is usually about 2500 meters deep, which is relatively shallow for the ocean. As a result, places where the plates move apart are also called Mid-Ocean ridges.

Close to the Mid-Oceanic Rug, the oceanic crust is relatively young and also warm. Over time, the crust moves away from the Mid-Oceanic Rug. The crust grows older, becomes cooler, which increases the density. This causes the crust to lie deeper, making the ocean 5.5 kilometers deep.
The part of the oceanic crust that is further away from the Mid-Ocean Ridge is already older, which means that more sediment layers have been deposited there, while with the younger crust, closer to the Mid-Ocean Ridge, fewer sediment layers could be deposited. This is proof that the crust at the Mid-Oceanic Rug is younger and therefore originated there.

Because the plate is stretched at starting divergent zones, it becomes thinner. You can compare this process to stretching an elastic band. Stretching will lower the crust. The low-lying part in the middle of the divergent zone is called a graben. The sides remain relatively high. We call these high-lying parts a horst. This causes some relief in the region.

With a divergent movement, basaltic magma emerges. Because basaltic magma is very liquid, shield volcanoes arise in divergent zones. These are volcanoes that are very wide, but not very high. That is because the liquid basaltic magma flows away very easily, making the volcano very wide but not high. The volcano eruption is effusive. These are eruptions that go relatively smoothly.

So you have learned how a divergent movement arises, what consequences this has for the depth of the ocean and what type of volcanoes and volcanism can arise there.

In the next video, Convergent movements are explained.

Видео Explanation of divergent plate boundaries and shield volcano's канала Geography Lessons