Science Grade 7 Unit 2 Lesson 1 MovingContinents Week 2 19 20

okay good morning everyone today we are going to do great seven inspired science unit to the book as you did to the changing earth even what does this what does this book name suggest what is it going to talk about what are we going to study in this book that how the earth has changed do you think earth was always like this how we see it today do you think the mountains were always there or they are have been they were just developed recently the rivers were they always there at the same place where we see them today these are other things that we are going to talk about in this book okay we have to develop everything slowly slowly to understand our earth so the first module that you're going to talk about is module 1 it is module number 1 the name of the module is dynamic earth the name of the module is dynamic earth and we're going to do lesson number 1 the name of lesson is moving coordinates it means that the continents are linked does that is it going to talk about that something like that we will see about that this is on page number 6 in your textbook unit 2 okay now these are some objectives that you must achieve by the end of this lesson the objectives are what was Alfred Wagnalls hypothesis Alfred Wegener was scientist and what was his hypothesis means an idea or claim he claimed something he claimed that there was something called pin joy there was something called continental drift what is all these things this is what we are going to study and our first objective then you know when any scientist he starts working on his hypothesis when he suggests his idea then he has to prove it to the scientific community that these are the proofs so you have to accept my work obviously if they have if the work of the scientists will get accepted only then it will be you know taught worldwide or it will be used as 2d or as fact if just one person has an idea it won't be you know any in any way beneficial so he started working on his idea and he started gathering some proofs some evidences so one of his evidences was parent fit of continence which we will see one of his evidence was related to the fossils one of his evidence was about the mountains and rocks and one of his evidence was about the Paleo climate and in this evidence we have something called glaciers in Africa glaciers are eye structures and Africa is hot so structures in Africa that is surprising thing right and then coal deposits in Antarctica this one also we will discuss later at the end at the very end we are going to discuss after all these evidences was his work accepted we will see this also now let's go through alfred Wagner's journey step-by-step now one day Alfred Wegener was sitting and he was just observing this map here this is the world map he was just looking at the continents and working on them he was trying to figure out something during his observation he observed that South America it looks like as if it is fitting inside Africa these continents they look like as if they fit inside each other can you see her this is Africa here and this is South America here if take these two continents and put them close together they look like as if they fit inside each other right how good they are how perfectly they are fitting inside each other looking at this continental fit that the continents apparently countless fit in very perfect way signal started studying other other continents also he started placing all the continents together like puzzle he started playing with these continents shapes like person and when he was working on this he saw something very interesting he saw that all the continents they fit inside each other it's not just South America or Africa all the continents they look like as if they are fitting inside region or as if they are part of each other but as if they have something to do with each other it's not like separate pieces of land by looking at this idea here that all continents they are fitting inside each other he brought his hypothesis he brought his idea now first of all let's discuss what is hypothesis now when scientist when scientist he brings an idea or an explanation from his observation which is not proved yet he has to prove it later on by doing some measurements by bringing proofs and evidences by doing some experiments only then when he proves his work his work is going to change from hypothesis and it will be established into theory okay in order to change hypothesis to theory you have to prove it to the scientific community by proper explanations and evidences and measurements experiments lots of ways but you have to prove your work you have to give all the answers ok at beginning when you are just working on something it is your hypothesis so this one was hypothesis of Alfred Wagner now let's study what was his hypothesis eyford whereas hypothesis was that all continents were once upon time joined together as supercontinent called Pangea he believed the scientists he believed that all these continents here they were together millions of years ago they were together as one as one supercontinent okay as one continent in other words you can say millions of years ago we had only one continent one giant big continent which he named as Vijaya now then what happened he continued his hypothesis and he continued to the idea of continental drift he continued his idea to continental drift now what is continental drift he said that over millions of years this big continent called Pangea it got split up it got broken up okay or it got into pieces and continents has started moving far away from each other continents are drifting far apart this movement of continents away from each other or drifting apart he named it as continental drift you can look here in this image here see how continents drifting see they are together then they got split up and then they are moving far away and far away and this is somehow we are close to our world map today this is the one now this would be Jaya broken up broken up more broken up more more and then our world today this is our world today right this was his hypothesis now again Alfred Wegener hypothesis was on two things one whole continents were together once upon time millions of years ago as super giant continent called Pangea then this Pangaea it got split up it got broken into different continents and continents started moving far away and this process he named as continental drift that the continents are drifting far apart so okay this was his hypothesis now after developing his hypothesis now what was the second step he has to do as scientist he has to go and collect evidence to prove his work to the world so what did he do first of all he started collecting evidences from fossils what are fossils fossils are the remains or traces of plants and animals that lived long ago long long long time ago millions of years ago some animals at large which existed at that time when they died normally when any animal or plant dies it converts in it is decomposed right by the bacteria but sometimes some parts or some animals or some clouds they do not get decomposed instead they get fossilized their remains are still left till today after millions of years also you can find some of their dead remains those dead remains are called fossils normally these fossils are found in sedimentary rock because fossils are formed under high heat high pressure in the Earth's crust that is why they are found in the sedimentary rock let's see how the fossils look like this is one of the fossils of plant another fossil of plant this is fossil of lizard like reptile structure this is fossil of fish and this one is fossil of dinosaur now how did Wagner start working wagner started working on this creature here called meso soros this one this creature which you see here is called meso soros this methyl soils is reptile which has gone extinct now but it existed long time ago we can see its fossils in different places on our earth now look here where do we find the fossils do you remember showed you at the beginning that South America and Africa they fit inside each other very name these continents now the parts of the South America and Africa which are fitting inside very well these parts here he found megasaurus fossil here also in South America also and here in Africa also in two different locations two different continents which are very very far apart from each other he found some fossils here half of the fossils here and half of the persons here now what does that mean what did Wagner argue let's see they argued that once upon time South America and Africa were together they were one piece of land so this creates your messes well it was roaming around on the land freely because it was one land so they were going here and there and they are roaming around here and there then later on they died they went extinct whatever happened after that went Pangaea started splitting what happened because of the continental drift South America went far away and Africa went far away some of the fossils are left here and some of the fossils are left here now magner further wanted to continue his argument now he continued his argument and said that it is not possible for this reptile called mr. Soros to swim all the way from this continent Africa all the way seven thousand kilometers and go to other continent which is South America it cannot even fly this big distance also so how is it possible that two different continents which are so far away which have different climates have the same species some fossils are here and some fossils are there how is that possible it means once upon time these continents which are apparently also fitting inside each other they were together and then later on they got split apart this was his evidence number one from fossils now this was only one type of fossil he found other fossils also let's go and find out what are the other forces he looked for one large fossil was there closeup Terrace the name of it is Glossop Terrace this plant one this plant structure here the fossil of this plant he discovered in many different continents he discovered in South America in Africa in India Antarctica Australia he found the fossil of this plant all around the continent all around the world all the continents South America Africa this yellow line going here South America Africa India dr. Hendron Australia now today if you look at the world map these continents are very far away from each other they are not close to each other and if you try to observe all these continents they have very different type of climate different weather Africa it is warm one right we have deserts and all that in Africa and practica is near the poles totally frozen Australia is different type of climate India different South America different so all these have different climates today now remember one point each type of plant or each type of tree plant species they grow in specific climates specific weather for example the date palm these dead trees we find them in UAE because this desert like environment hot desert environment is suitable for the dead pumps that is why you fall you find these dead pumps in Saudi Arab in UAE in such countries you know which we call the Middle East do we find date pants in Australia do we find these date pants in UK no we don't find it them there right because every plant is going to grow in the conditions that is required for that plant to grow similarly this closet dress also requires some type of climate conditions or weather conditions those conditions that it requires is called the temperate climate now millions of years ago with all these continents were together this part of the this yellow line here it must have supported that climate it must have been in an area which supported the temperate climate that is why Gloster Chris was able to grow in South America Africa India and optic Australia ok this was another evidence that he brought similarly it brought some other evidences also these are also very interesting evidences now if you look at this one this creature here sigh dog madness this one is the fossil of this creature was also found here in Africa and South America and look at the pattern here it is found in the same exact place where South America and Africa they are sitting inside each other the same boundary you know the boundary here at the same location here in this line very perfect line he found the fossil of this creature sign onethis if you try to look at this one mr. Soros it was also found here in Africa and look at it how it it is found here in this small island here and then this India and then Antarctica and even even if you look at the pattern here Africa and India they are they look like as if they were connected from here and you know at the same places he found the fossil India and in tactical looks like as if it was connected on these areas here and at the same place he found that the fossil of this creature was found in at the same pattern same thing with Glossop Terrace which already discussed South America Africa India and talked ago it was thought every or in all the continents so this was one evidence that he found Alfred Wagner's first evidence was that he found same fossil of the same species from the same age in two different continents which have totally different climate totally different they are very far away from each other so how can you have same fossils from same age in two different continents this was his first evidence let's go to second evidence tough evidence from mountains of rock formation this picture here what is it show it show us an area where we have lots of mountains you call it mountain range now what will happen if try to split the mountain see we said that long time ago Pangaea got split up right we said that the earth got split up it was one supercontinent so if it got split up it means at some point in some places the mouthpiece must have got split up let's see what would have happened if the mountains would have got split up half of the mountains should be somewhere else half of the mountains should be somewhere else in another continent and we must have an ocean in between now if it got split up something like that must have happened now let's see if Alfred Wegener was able to find some evidence from mountains and rocks or not let's see now when Alfred Wegener he started studying about the mountains and rocks he found the same mountains from the same age same composition same chemistry at both sides of the Atlantic Ocean in I'm North America here in Africa here Greenland here see mountains you see this area here it is marked in small dotted lines here these all these mountains all these mountains here they are me we are made up of same type they are same type made up of same material they have the same age the chemical composition is the same everything is same it's just like half part of the mountain is somewhere else and half of the mountains is somewhere else now how is that possible how can the same places which fit inside each other the continents which apparently look like they are fitting inside each other they have the same forces they have the same mountains or same rocks on either side how is that possible now one of the real example that will give you for the mountain correlation is this one this will happen as she mountain ridge at Eastern Greenland mountain ridge half of the mountains are here and half of the mountains are here same mountains but one half is the in the Eastern Greenland and the other half is in USA and Canada this one is in the USA and Canada the Appalachian mountain range and this one the eastern Greenland mountain range is in Greenland which is totally in different place and you have an ocean in between them how can you have same type of mountains half of them in another continent in half of them in another continent it means these mountains they must have got split up and that is why but now the continents they have drifted apart but long time ago they were together so he proved his point with the second evidence of mountain correlation now let's go to this other evidence another evidence was from Glacier features what is the glacier glacier is slowly moving river of ice formed by the accumulation accumulation means constantly come you know compiling something constantly when there is snow on mountains and this snow starts going down slowly slowly you know it starts moving and when it is moving in the form of ice you don't call it river then you call it glacier because it is the ice that is moving it's not the water that is moving you know so again glacier is slowly moving river of ice okay now let's look here can you see here this ice is moving here the ice moving here between the mountains it is now where is this ice normally found where do we find glaciers we find glaciers in areas which are very cold freezing climate right so and freezing climate is normally close to the close to the poles now let's go forward and see this one now this car is drifting this is car it is drifting here when the car drifts here the car leaves some marks here right you have seen this with car drifting marks you have so you must have seen them on roads many places where with normally boys they are you know doing this car drifting why do these marks are left here on their audial because this car is solid and this road is also solid but it is moving on the road with the force it is going to create some marks similarly when glaciers similarly when glaciers they are moving on the mountains or they are moving for on the rocks they create deep scratches they create deep scratches in the rocks as the glaciers they move now this structure this one you know these marks which are created by the glaciers they are called glacier grooves they are called glacial groove these marks are created by glaciers moving on the rocks or you can say that river of ice where it moves on the rock now ice is solid rock is also solid but when you have lot of ice moving on the rock it is going to create scratches on the rock those scratches those marks are called glacial grooves now how did Alfred Wegener find out any evidence from glacial grooves let's study about that now first thing was the pattern he found the pattern of glacial grooves see these glacial grooves are found in many different continents from millions of years ago ok from many years ago now where he started studying these glacial grooves he found them in South America here Africa here India here Australia and Antarctica here now these continents apparently they are the same cone the same place which is fitting inside each South America sits inside Africa from this part here Africa fritzen Antarctica India's this part fits here Australia here it looks like it is one piece of land here which supported glacial grooves at that time this is one type of thing one type of evidence he said but there is much much more interglacial grooves because of glacial grooves he he got many many more ideas let's see what is it now one evidence which was talking about is Paleo climate evidence what is Paleo climate evidence video climate evidence is an evidence which is from the climate of past geological age what does that mean from millions of years ago the climate was different at different in the continents because continents were at different location at that time now see if something is close to the equator on our in our earth if any continent is close to the equator it normally receives warm weather if something is close to the poles it receives it has freezing climate there right but these God is according to Alfred bangle has moved and if they have moved that means the climate has changed with time at some time millions of years ago that to climate was something else then it started moving moving and it went to another location and after some time the climate was different there so studying this past climate from past geological age is called the Paleo climate evidence now how can you have glaciers in Africa Africa is so hot it has warm weather it cannot support glaciers how can you have these ice structures in Africa structures are always there including areas which are close to the poles you cannot have AI structures in Africa so how can we have the Glacial grooves in Africa how Africa is warm continent which has average temperature of 26 degree Celsius but in order to have glacial grooves you must have freezing temperatures right so Alfred Wegener said that Africa must be closer to the poles in the past geological age he said that this Africa this continent here called Africa which is closed equated today it is current location millions of years ago it was not here millions of years ago Africa was somewhere close to the poles that is why there were glaciers in africa at that time that is why at that time when these glaciers they were moving they created those deep scratches in the rocks in the African land and we find the evidence of glacial grooves today if Africa has not moved if Africa was here always then how can you have glaciers it's not possible at equator we have warm then we have warm climate we have warm temperatures at most of the times this was his one of his evidences from Paleo climate this is another one also let's go to that one now anyways again Paleo climate evidence yes one more thing you must understand first of all what is an equator and what is pole so added this slide for you see this line here this line here this one this one the red color close to the red color this is the equator these continents or these areas of the continents they are normally receiving you know more sunshine they are having different type of climate we call it tropical zone okay and poles means this area here the down one blue color and up blue color we call them polar and subpolar zones okay again see this African continent it is on equator today which means it is receiving too much of Sun fall and rain this sunshine and rain here and decline and the temperatures are high and if the temperatures are high you cannot have glaciers but we find glacier grooves here in Africa how can you have glaciers in Africa it means before long time before Africa was not here Africa was somewhere down here somewhere close to the poles here that is why at that time Africa had freezing climate at that time glaciers form at that time the glaciers they were moving on the rocks they created this deep scratches and that is the evidence which we see today but it is from past geological age okay now another evidence do you see this cold this picture here the coal here this is called but this is called bituminous coal this coal here is called bituminous coal it is used for creating energy okay you are using it today also to create energy now this coal as you remember that coal oil and natural gas are fossil fuels and fossil fuels are the energy sources that are created from fossils and fossils are what dead remains of plants and animals from billions of years so this goal is made from this plant when this plant here it dies okay for millions of years okay when it dies and it is under the Earth's crust under high heat high pressure for millions of years then this coal is formed okay now this plant from which this coal is formed is the ancient plant this plant is the ancient plant this plant can only grow in warm and wet region region where there is maximum sunshine and lot of rainfall it will only grow there okay this plant will only grow in an area which is warm hot and which is wet red means receiving more rainfall and from this plant when this plant dies and it is under the Earth's crust under high heat high pressure this coal is formed which is called bituminous coal now what is the click here this coal deposits are found in Antarctica where is Antarctica near the poles and tactical is freezing continent right Africa is freezing continent do you think Africa is receiving lot of sunshine and it has warm weather there and it is receiving lot of rainfall there do you think freezing continent is receiving all that no right but this school is here these coal deposits are found in Antarctica how the plant from which this coal is made it cannot grow in Antarctica what did Wagner argue how can this coal exist on continent which is freezing freezing continent cannot allow swamp plants to grow right so he said that and particle must be near the equator in past geological age again if have this coal deposits in Antarctica if we have this coal bituminous coal in Antarctica okay which is made from plant which can only exist in warm wet climate that means Antarctica had different type of climate before and in order to have different climate before and tacticals location on earth map must be somewhere else it must be somewhere close to the equator because near the equator you have more sunshine right so tactical must be somewhere close to the equator before then at that time billions of years ago this flood ancient swamp land must have grown up there when it grew there and then it died and then it was under the Earth's crust under high heat high pressure for millions of years at that time okay then the coal deposits were formed okay by the time Antarctica was moving the continent was drifting and drifting and drifting and it came towards the pole this was vagueness argument or his evidence from coal deposits now these were the all the evidences that Wagner was able to collect okay so let's summarize Wagner's evidence the first evidence that he brought was that the continents they look like as if they are all fitting inside each other like puzzle right second one was evidence from the fossils correlation what were the fossils that we have studied one fossil that we studied was meso Sorrels that reptile-like thing it looks like lizard and the second one that we said it was the plant Glossop Terrace then third one was from the mountains and rocks mountains of rocks correlation he found half of the same mountains at another corner and another half of the same mountains or rocks in another continent these mountain these rocks has same age we have the same structure same chemical composition but they are at two different continents this was an evidence for him that these two continents were once together that's why we have same mountains in two different countries which are thousands of kilometres far away from each other then there was evidence from the glaciers patter and the delicious they are they were in all the continents they form pattern that the areas which are frigging inside each other you find glaciers in those areas then there was an evidence from the Paleo climate which was Africa has glacial blues which means that Africa has freezing climate in past geological age second evidence was Antarctica has coal deposit which coal deposit bituminous which is formed from the fossil of swamp not that will grow in temperate climate only warm wet climate this means Antarctica was closer to equator and it supported swamp lands before it is not supporting today today it is freezing continent but before it was not before it was at different location it has drifted and it came to pull now these were the evidences that Wagner was able to collect okay now after collecting all these evidences now when now he went to the scientific community then then he went to the community he said that see have worked on all these evidences have very strong evidences and he gave his work and he wanted it to wanted to build his hypothesis into theory but what happened there was big challenge that magnet faced Wagner had very strong evidences to prove that the continents were once together but he was not able to explain how the courtiers are moving on the solid rock of the ocean flow now once again see our continents what are they what is there in our content if you go and look at the soil and everything what is it we have rocks right our earth crust is full of rocks now if you go deep inside the ocean and you go to the ocean floor what is there we have rocks near also now this massive continent how can it move on the ocean floor how can move on the ocean machine floor is also rocks this is also rocks - you know this massive rock how can it move on another massive pieces of rocks how can it drift on it it needs large force huge amount of force to move on you know the friction how much it will be between when two massive rocks they are you know moving on each other so what Wagner was not able to explain that how these continents are moving he was not able to explain even he was confused how can continents move on the solid rock of ocean flow there is something that was missing here he could not explain it so his hypothesis was not accepted wagner's hypothesis was not accepted guys Vagner he died in 1930 ok Wagner died in 1930 and when he died his work was not accepted at that time where nures work was accepted forty years after his death now people do you think they will just accept his work without reason no right if they accepted his work after forty years of his death it means there must have been some new discoveries which led them into accepting his work what are those new things how was vagueness hypothesis accepted how all these things happen what were the new you know new ideas that came into existence these are the things that we are going to learn in the next lesson in this lesson we have only studied about diagonals observation that the continents are fitting inside region then we studied about Wagner's hypothesis that yes once upon time all the continents were together as Vijaya and then they split up then the continents they were drifting apart he called it continental drift then he started collecting his evidences there were five pieces of evidences which we discussed but after collecting all these evidences the last thing where he was unable to explain was how the continents are moving on solid drop of the ocean floor this was his challenge and he could not prove it he could not explain it so his work was not accepted and he died so this is the end of the lesson best of luck