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Plate Tectonics -- Geological Features of Divergent Plate Boundaries

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Plate Tectonics -- Geological Features of Divergent Plate Boundaries

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Before we go into possible theories
as to why plates actually move,
what I want to do in this video is
think a little bit about why we see the
geological features we do see
at plate boundaries, and in particular
I want to focus on the
features we see at divergent plate boundaries,
where the plates are moving away
from each other, where new land is being created
like we saw in the mid oceanic ridges,
where we see new land being created right in the center
and moving outwards from them.
So to do that let's think about the different layers
and actually I want to make one quick correction
on the last video.
Over here I had drawn these arrows going in that direction
and based on how I defined them, they should
be going into the page and so they should've
had these Xs here.
Now with that out of the way
let's draw a little diagram
of what happens at the early stages
of these divergent plate boundaries.
So you might have your
here you have just your crust,
and maybe it's continental crust...
This right here is the earth's crust,
and then you have the solid part of the mantle.
And the combination of them is the lithosphere.
And then you have the liquid part, the superhot part
of the mantle, this down here is magma.
It hasn't solidified, it's hot enough to be in the liquid state.
And all of this combined, this right here,
we consider the mantle.
Now, there's some debate, and we'll talk about
this in the next video, of how hotspots actually form
it could be these mantle plumes that start
at the border between the mantle and the core,
it could be some type of convection current
in the actual mantle, we'll talk more about that in
the next video or maybe a few videos from now.
But let's take it for granted that hotspots form
in the mantle, so let's say we have an area
of magma right here, that is particularly hot.
Let me draw it in in another color... pink.
So this is particularly hot magma here.
And we know, or maybe we don't know,
if you take the same material and you make it hotter,
it's going to become less dense
because the particles essentially are going to
bump into each other with more kinetic energy
and have more space in between them
and so this really hot part of the magma
or this really hot part of the mantle
it is going to move upwards,
because it is less dense, it will have buoyancy.
And as it moves upwards, it'll heat up
the things around it and it'll
eventually make its way into the lithosphere
and it'll be able to break through the lithosphere
because it's so hot it can melt its way through.
So let's fast forward this a little bit,
so this is Step 1 up here.
Now Step 2, this hot magma is

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Plate Tectonics -- Geological Features of Divergent Plate Boundaries

Plate Tectonics -- Geological Features of Divergent Plate Boundaries