hi guys in this video we are going to be looking at tectonic activities tectonic processes and tectonic features and this is for the GCSE unit one and the first you know the first chapter of that unit which is tectonic hazards so I'm going to be going over the 4 plate margins today and talking you through the processes and the features so if we look at the diagram that you've got in front of you you see on the left hand side we'll start off with the district constructive margins now constructive margins as you can see from my red arrows or whether the two plates are moving apart from each other they've been pushed apart and this is also called a divergent plate margin now the mechanism of movement obviously for all four of these margins or convection currents within the mantle that magma is heated by the radioactive decay in the core that's the heat source rises gets up to the top of the lower crust sticks through the asthenosphere remember and then drives the plate see the report all together or side-by-side so that is the mechanism for all four of the plate movements but if we just start here with the constructive plate margin we can see that here with the margin is between two ocean crusts so we've got ocean crust on both sides the margin is in between which Lisa a relative gap for the magnetic pole shop and be able to get out of so the magma pushes up from the mantle rises to the surface normally underneath the sea creates new ocean crust and the plates are pushed apart just very very slowly so these two plates are moving further apart and this magma is pushing up and depositing lava on the ground which is solidifying and that's become a new ocean crust the other thing you have to think about here's that's sometimes we can have a very very strong convection current beneath the surface and that will extrude lots and lots of lava which will mean that we have a buildup of lava on the sea floor which may well reach the surface and form an island and Iceland is an example of this so that is our constructive margin or next margin on the right here's our destructive margin which is also called a convergent margin because as you can see from the two red arrows the two plates are moving together so what you've got here at this margin is we've got ocean crust and continental cross now if we remember ocean cross the characteristics are they is very thin it's very heavy and it's very dense so it gets pushed underneath or subducting underneath the continental crust which is thicker more buoyant and lighter relatively lighter so that stays up and the ocean crust dives beneath it so what happens is the ocean crust gets pushed beneath and it goes back into the mantle and it starts to melt now due to the increase in pressure and friction here it means that the magma the melted magma the melted crust becomes lighter than the surrounding rock because it's hotter and it starts to rise up through the crust and through the continental crust and it extrudes it the surface as a volcano now we also get four earthquakes occur in here and as you can see as the ocean crust dives beneath the continental crust we have a little red circle which corresponds to the idea that we've got a pressure and friction increase so pressure and friction build and that crust will kind of snag or get stuck as it's pushing down over time it will jolt forward and that job for which will provide energy which will be released and that will be the earthquake so this is a very destructive zone we have very destructive earthquakes here and very destructive volcanic activity we tend to have very explosive activity here and we also have composite volcanoes because if we think about it the magma here is kind of quite contaminated it's not just magma from the mantle which it is here so this magma is highly explosive and we tend to get at composite volcanoes formed because the lava tends to be very sticky now back to our constructive margin the lava tends to be not sticky non viscous so it spreads out so we get shield volcano so this is a link as well to shield volcano composite volcano and they are the--to these two first two margins wonder neath now we've got a collision zone which is actually also a destructive margin because the two plates have been destroyed it's also convergent margin because as you can see the two plates are pushing towards each other but here the difference is we've got continent and continent colliding so because the characteristics of both are that they are both buoyant and thick neither of them are subducted they're both pushed up so we end up with a feature called a fold mountain we also end up with pressure through at the margin between these two plates so we will end up with earthquake zones either deep focus or more shallow focus and these again can be very very destructive margins you don't get volcanic activity here but you do get the earthquake activity here and they tend to be very destructive earthquakes because of the amount of pressure that will build up and therefore once the pressures released that's released in the form of waves that cause you know huge amounts of devastation around the world so the example here will be the Himalayas as the hit as India's pushing into the erosion continent and the Himalayas are formed the Himalayas at the four mountains and we get lots and lots of earthquake zones here as well as the two plates pushed together so that is our collision zone and finally we've got our conservative plate margin which as you can see the two plates are moving in parallel to each other so they're moving in opposite directions or as is the case in San Francisco they could be moving in the same direction but at different speeds so what we can see here is that the plate margin is uneven this means that at some points there will be a snag in or or catch or it will stop it will get jarred and the pressure will the plates will continue to push against each other it will build up pressure and then suddenly at some point and those two plates will move past each other and that is where our energy is released and we get our earthquakes so again this is a very very active zone the conservative zone is very active and it produces very very very destructive earthquakes so the top two plates is where we get volcanic activity the dish constructive in the destructive margins and the two bottom and plates the collision zone the conservative we tend to get earthquakes and no volcanic activity but these three obviously you can see we get earthquake activity at these three so they are our four margins which you will need to make sure you know for those exams for unit 1 you'll need to know the processes and you'll need to know the features as well