hello great then today's video is all about mantel's convection current this is still part of your study about plate tectonic theory as a review we did say before that plate tectonic theory is a theory about moving lithospheric plates which leads to different types of plate boundaries such as convergent divergent and transform fault this theory basically supports continental drift theory of alfred wegener what makes this theory more special is that it answers that one question which alfred wegener failed to explain back then and that question is how did the plates move today's objectives include describing the possible causes of plate movement and recognizing the process of convection current in the mantle for sure when you were in grade 7 you have encountered the terms convection current it is actually one of the methods of heat transfer along with conduction and radiation convection is the process by which heat is transferred by movement of a heated fluid such as air or water the warm part moves up and the cold part moves down but why does warm air or warm water rise why does cold air or cold water sink the answer is density density refers to the compactness of molecules if those molecules are heated there is increase in temperature they gain energy and move allowing the area to expand with this the gas or liquid becomes less dense than its original condition it's lighter so it would move up if the temperature decreased the molecules will move slower and the area occupied by the molecules will be smaller with this the density will be higher since the molecules are more closely packed together now the gas or liquid becomes denser and so it will go down same thing happens to magma in the earth's mantle the nearer the magma to the outer core the hotter it is the farther the magma from the outer core the colder it is the hotter magma will go up and once its temperature decreases it will go down the colder magma will go down and eventually be heated once its temperature increased it will go up again the cycle goes on and on creating what we call convection current in the mantle this is the reason why plates move the plates are like eggshells on top of a butter which is the asthenosphere or the upper part of a mantle once this batter starts to move the eggshells will also move here you'll see various direction of convection currents in the mantle some follows a clockwise direction and the other counterclockwise these directions or flow of convection currents lead to the different types of plate boundaries for example convergent type of plate boundary here you'll notice how the convection cell on the left side follows a clockwise direction while the convection cell on the right side follows a counterclockwise direction apparently these convection cells allow the plates above them to move towards each other for divergent type of plate boundary the convection cell on the left side follows a counterclockwise direction while the convection cell on the right side follows a clockwise direction allowing the plates above them to move away from each other this week you must have two outputs in science one is to create a pamphlet about mantle's convection current procedures and rubrics can be seen on pages 15-16 of your module be creative the other one is an assessment which has three questions and you have to write your answer on an intermediate pad if you have any question notify your teacher the soonest thanks for watching this video