OK Head Squeezers we got a volcano-tastic experiment for you today in the Live Experiment
section.
We're down here in Mount Etna in Sicily, an active volcano, but the question always is
what's the difference between lava and magma?
So we're gonna do a little bit of modelling experiment here so we can't create our own
volcano because it's pretty hot, so what we're doing instead is creating a model of a volcano
and the earth's crust in this glass here.
So just to start us off we have some red wax and all it is, is a candle that has been chopped
up, and it's pretty well themed in terms of colour for molten rock.
Nice red colour.
Lave goes quite red.
It does.
So what we're doing is we've chopped it up with a knife and popped into the bottom of
this flask here and what we're doing is melting it down to soften a little bit.
So this is going to represent the molten rock underneath the earth's crust.
So this is going to be under the earth's crust so this is going to be magma.
So we do need some earth's crust on top of that so what we're gonna do is put some sand
and some soil on top of it.
OK I get to hold the funnel for this section.
So we're going to do is add some of this beautiful dark volcanic sand into our flask here so
we want to cover the molten rock that's gonna be underneath that.
Excellent.
And this is a really good representation of what Mount Etna is doing specifically because
underneath Mount Etna there is a rock with a large magma chamber full of molten rock
just like we have in this experiment.
The last thing we add is loads of water so that's going to represent the air around the
volcano and it's also going to keep us safe from any splatters of any molten wax.
So you have that water bottle next to you here?
Yep.
So we're just gonna top this up.
So what's gonna happen as the earth's heat melts the rock underneath it's going to build
up in pressure become less dense and it's going to want to break out of the earth's
crust so what we should be seeing in a moment is an eruption.
It's gonna be a volcanic eruption and it's molten rock under the earth's crust which
we call magma is gonna rise through the earth's crust and become lava.
When it's settled we should create a volcano.
Now, it's gonna be focused in one particular spot which we're heating underneath and that
reservoir of molten rock is called the magna chamber.
So it's when the pressure in that builds up to a point where it can't take it any more
we're gonna see a volcanic eruption.
So on a volcano like this you get the main summit which is just over this ridge at the
top but you also get lateral events which are a little chambers that come out into the
side of the volcano just like this crater behind us and those little craters will spew
out magma a well, it will just come out of the side of the main chamber.
So the pressure now inside is building up, and that chamber, that reservoir of molten
wax, is starting to push its way through and it will actually make a little dome on top,
some great scientific studies and animation of Mount Etna breathing.
Going up and back down going up and back down.
And that's because the pressure inside pushes the surface of the volcano up just like we're
getting here.
I can feel on the cylinder, the cylinder, vibrating.
You will find that on volcanos, you get tremors just before you get an eruption.
OK so we have some lava bubbling up we have some ash plumes going on, and some of the
lava is building up at the base of our volcano there.
So the lava is now pushing up through all the different places on the volcano so where
ever there is a magma chamber you're gonna get all these different lateral events and
the main chamber itself.
The main chamber in our volcano has come up right at the back.
So we can tell a lot about what the lava is actually made of by the density of the lava
that actually erupts when a volcano erupts.
In this case it looks pretty think so in our model that means it contains a lot of a compound
called silica.
So the more silica lava has the thicker it is, and the closer it stays to the main vent
so it creates quite a triangular volcano shape like we have on Mount Etna.
If we were to have a much thinner lava then it spreads out a lot more, it's a lot shallower.
So you can tell a lot about the composition from the shape of a volcano.
So there we go head squeezers a live experiment about a volcano on a volcano and if you want
to see other films that we've made down here all about volcanos then just click the button
and we shall see you next time on Head Squeeze.