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We've already talked a lot about plate boundaries

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Where essentially new crust material has been created and the plates are actually moving apart

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we call these divergent boundaries, and the example we showed of this was the mid-atlantic ridge

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Where essentially new crustal material is being created

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the other side of the equation you have areas where plates are ramming into each other

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we see that over here where the nazca plate is running into the south american plate

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we see it over here where the pacific plate is running into the phillipino plate- they're running into each other

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so what happens over there? so what we're gonna do is just go through the different scenarios.

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the general idea is that one plate is going to get subducted under another

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they're ramming into each other one is going to get essentially pushed under the other one

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this diagram shows some subduction over here

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this is essentially an oceanic plate being subducted under another oceanic plate

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so not too different than what might happen when the pacific plate runs into the filipino plate

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right over here, then on this side of the diagram

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we see an oceanic plate and the oceanic plate getting subducted under a continental plate, right over here

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and this is what's happening when the nazca plate is getting subducted under the south american plate

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and when that happens you have a couple of things

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so you have the oceanic plate being pushed under

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and what happens at the same time the continental plate gets pushed upwards causing mountain ranges like the andes

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and that's exactly what causes- what has created the andes

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it's the upward force from the nazca plate being pushed under the south american plate at that coast line

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and what you're also going to see is, and if you can imagine you have these huge plates grinding past each other

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it's not a very smooth process, every now and then you reach a breaking point where hug amount of energy

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get released so you're also going to see a lot of earthquakes in those areas

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and we know that chile has a lot of earthquakes

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and then on top of that, this is going to result in a lot of heat

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and a lot of friction of the plates grinding past each other

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essentially allowing magma to form at that part of the rock

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and it's getting so heated that you'll also have volcanoes in these areas

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where essentially something is being subducted underneath a continental plate

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now we also talked about what's happening in the pacific

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where we have the pacific plate being subducted under the filipino plate

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that's what we keep referring to over here

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and that's doing a couple of interesting things

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so whenever so have subduction you have trenches

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but it's most interesting - or at least in my mind

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the deepest trenches have been created where you have an oceanic plate being subducted under another oceanic plate

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so a couple of things are going to happen

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you're going to have deep trenches form

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you're going to have a trench form

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over here you see in this diagram we also have a trench

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and the first example

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but you have trenches form where one oceanic plate is being subducted under another

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and then you have that same type of friction that you saw over here create volcanoes

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and those volcanoes will initially be under water volcanoes

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so if these are both oceanic plates, or we're dealing with oceanic crusts

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at that point of the plate it doesn't have to be entirely and oceanic plate

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and there'll first be underwater volcanoes

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but as the lave piles up and hardens

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it'll eventually turn into a group of islands

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and we've had that happening where the pacific plate runs into the filipino plate

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and first we have the trench

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let me just draw everything right here

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so, this is the boundary, roughly, roughly speaking

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this is the boundary between the two plates

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the pacific plate and the filipino plate right over here

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and where it's being subducted you have the mariana trench

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which is the deepest trench in the world!

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it goes down eleven kilometres- eleven thousand metres!

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that's deeper than mount everest is high

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mt everest is about nine thousand metres high

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and we'll see that's also due to another convergent plate boundary

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another plate boundary where plates are running into each other

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so not only do you see the mariana trench here

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because one plate is being subducted under the other