Our last hazards video ended with us saying...

As you'll see in our next video,

the real action happens along the edges of the tectonic plates.

So, now it's time to take a look at plate boundaries,

sometimes also called plate margins,

which are all of the parts of the world where one tectonic plate is next to another. (MUSIC).

Constructive sometimes also called divergent plate boundaries exist in the parts

of the world where magma is rising up in the mantle below,

this rising magma cools off and spreads out.

Some of it solidifies and creates new crust which begins

to slowly move apart as two separate tectonic plates.

These types of boundary mostly appear at the bottom of the sea.

(Under the sea).

There are some places like Iceland where you can actually

see evidence on land of the tectonic plates splitting apart.

So, what type of hazards do we find here and why?

Let's start with volcanoes.

Some of the magma along with gases like carbon dioxide can

melt through the crust and get released out of the surface,

which is basically what a volcanic eruption is.

So, yeah,

we get volcanoes often with lots of lava.

Earthquakes do happen at constructive boundaries,

but they aren't usually that powerful.

You see an earthquake happens when tectonic plates

get stuck or grind against each other.

And it just doesn't happen very much at this kind

of boundary because the plates are mostly moving apart.

Destructive,

sometimes also called convergent boundaries are areas where

tectonic plates are being carried towards each other.

But there are actually two different types.

If an oceanic plate is moving towards a continental plate,

the oceanic plate is forced underneath because it

is denser in a process we call subduction.

As the oceanic plate sinks into the mantle, water and things like

dead plankton on the sea floor are dragged down with it.

These are turned into water vapor and carbon dioxide which bubble upwards

and melt through the continental crust above get trapped in the rock.

Pressure begins to build up much like it does when you shake a bottle of fizzy drink,

and eventually the pressure in the crust becomes too great and the gas

and lava violently explode out of the rock in a volcanic eruption.

Extremely powerful earthquakes can also happen in these destructive boundaries.

The oceanic crust doesn't simply slide gently past a continental plate.

These huge rough slabs of rock are constantly

grinding against and getting stuck on each other.

And when they do get stuck, the continental

plate starts getting dragged down with the oceanic plate.

It builds up a huge amount of energy as this happens.

And when the plates finally become unstuck,

the plate violently jumps upwards,

releasing all of the stored energy and causing intense shaking in the ground.

We know this as an earthquake.

The second type of destructive plate boundary is known as a collision boundary.

The big difference here is that both of the tectonic plates are continental,

so they have roughly the same density.

They crash head-on and crumple upwards, creating what we call fold mountains.

You can see this is happening between tectonic plates like the Indian and

Eurasian plates where the force of the two plates colliding has created a mighty

Himalayas mountain range.

As you can imagine, the process of forming a mountain range isn't as smooth.

The plates grind and crack and buckle upwards over millions of years

and at times they get locked together and get stuck on each other.

Eventually, the plates build up enough energy to become unstuck.

The plates jolt back into movement and an earthquake is created.

Oh and don't confuse these mountains of volcanoes.

There's no magma rising up from underneath them,

so you don't get any volcanic eruptions at collision boundaries.

Conservative boundaries, sometimes also called

transform boundaries are so named because

the tectonic plates are not being constructed or destroyed here,

so it is conserved which means to be kept the way it is.

These conservative boundaries happen at places where two

tectonic plates are sliding past each other,

either in opposite directions or in the same direction at different speeds.

The edges of the plate get stuck on each other as they grind past and

you probably know the rest by now,

it builds up energy and after a while they jolt back into moving again

and the energy gets released causing the ground to shake,

earthquake.

Following the same rules as before,

there is no magma rising up underneath the crust at a boundary like this. So,

you guessed it,

no volcanoes.

And that will be all for this video.

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As always,

you've been listening to The Mountain Man and watching the work of Michael Deluxe.

Remember,

keep it simple. (MUSIC).