Lecture 11

Namaskar, welcome back. So, last lecture we talked about the convergence of continental and oceanic plates. Now, we will talk about what happens when two continental and continental plates meet. So, the best example of this on our earth is the Himalayan plate. There is a story behind this. Initially, the plate in front of the Indian plate was an oceanic plate and it was subducted first. And after that, when it was finished being subducted, two collision plates came face to face and we call it a collision zone. So, that is why whenever you read old research papers or literature, you will find that it is also called a collision zone. So, this is the best example of the Himalaya plate. So, let us move ahead in this. So, if you have two plates, continental and continental and the density that we have been talking about in some lectures plays a very important role. So, the density of these two is the same. And because of the same density, there will be no subduction in each other, there will be a collision. And that is why the height of the Himalaya plate is so high. So, the reason why we have played this game in Himalaya is that this collision always makes a very high mountain range. And we have its remains and evidence. So, when we talk about its signature, we have Mount Everest, which is the highest point on the earth. So, let us know a little bit about this, how it will happen and where there are such convergent plate boundaries, where there are such gigantic mountain ranges, or we can say that there are mountain ranges. There are three examples, there are Alps, there are Himalayas, we call Himalayas, some people call it Himalaya, so it would be better to call it Himalaya. And there is Ablation, these are the three locations where we get such collision zones in the world. Now, if we talk about continental-continental collision, and as I said last time that we will mostly talk about the Himalaya, because it is very close to us, our Indian plate is made in it, so it is very appropriate to discuss about it. So, if we look at it, then as I said that the subduction initially took place in it, and because of this, this plate, this continental plate is also there, some portion of its continental plate has been dragged down. So, this old crust, when it went down, and here the Himalaya is also there, so it is very close to us. For example, we are in Kanpur, so that is the part of the Indo-Gangetic Plane, and if we go to the upper area of the Himalayas, in the higher Himalayas, then we get some evidence there, which tells us about volcanic activities. So, in the earlier time, when this subduction took place, initially when we had the oceanic plate, the front part of the Indian plate, when it was subducted, then we also had volcanic activities there, but now its source is finished. So, these two plates, the continental plates have come together in front of us, so that is why we do not see the remnants of it now. But yes, the evidence of the old activities is still there. So, let us see a little further, this is the world's most prominent, which we will say that it is very attractive, this landform, Himalaya, let us know a little more about it. So, and the things I have told you, because these plates do not sink, because their densities are more or less similar. If we say that how was the prologue process of the Himalayas, then it has been seen that the front portion of the Indian plate, the front portion had the oceanic crust and the continental crust was attached to it. So, what we are seeing now, this is the Indian plate, this is the part of the Indian plate, both were there. So, initially what happened is that because the oceanic plate and the continental plate came in front of us, so this is light, this is heavy, so this started subducting you. So, we will say that if we want to understand the whole process of the formation of Himalaya, then it is necessary to understand this thing and this front part of yours, this portion of yours, which was of the oceanic crust, this was the river, we used to call it Tethys, this was the sea. The sediments of Tethys, which was the sea, we also get the remains of it, the marine deposits that we call there. So, these are the sediments of Tethys. So, there is no ocean there, so where did it come from? Along with that, what we also get in this is that there are volcanic rocks here and there are some remains that show volcanic activities, which were seen earlier when the oceanic plate was being subducted. So, this movement is always, as it is told in Aeros, that this plate kept coming this way and this kept subducting inside it initially. So, this was its first stage. After that, it came closer. So, this is what we call the closer of Tethys sea. So, this closing started here because the two started coming closer to each other and slowly these activities, which are volcanic activities, started to stop. And when this portion of it is completely finished, which we will say that its source is finished, when the oceanic plate is not going inside, then the volcanic activity will not take place. So, all this is completely finished. And what happened at this time, due to the collision of these two, what we call the formation of the collision zone, this is formed. So, these are the stages. It is important to understand this. So, here the ocean, which was seen earlier, in that we have this ocean, which is closed. And because it is finished, because these two plates came close to each other and this collision started. So, that is what we call the collision zone. And then, these clusters started to form in the Himalayas. Although some elevation was gained when the subduction was taking place, but after that, when the collision took place, then this is the fastest growth of it, we say. The growth started very early and very early these mountains started to form. That is why we also say that these are the youngest mountains on this earth. And after that, in front of it, these deposits, sediment deposits started to form, which we now call the Indo-Gangetic Plane. This started to form. And so, in this, these thick things are the same. Collision is still taking place between these two. And still these clusters go up. And this portion, which is here, we say that the continental crust is here. This part is Tibetan. When we call it, we call it Tibetan plate. And this one is your Indian plate. So, these two plates are colliding with each other. They are both continental plates. So, if we look at the final situation, then we see that this portion of yours was the older oceanic crust, which is completely finished. And this continental crust, which is the Tibetan plate, and this portion will be of the Indian plate. We have shown this picture from the other side. So, this will be your Indian plate because it is of this subject and this will be your Tibetan plate. So, these two are colliding with each other. And what we are getting is what we call an accretion zone. And we also call it wedge, sediment wedge, in which all the rocks and layers of sediment are being deformed, which is shown in this. So, there is deformation in this, which we call folding. And along with this, we can see that its topography is also increasing. So, we have told you about how the Himalayas were generally formed. This also shows a picture that when your oceanic plate was initially subducted, this was your Indian plate, and some portions were of the oceanic plate in front of it. And this is of the Tibetan side, or you can call it Asia. So, this is your Indian plate, and this is your Tibetan plate. So, this portion was of the continent plate, it was oceanic, that is why it was subducted. And after that, finally, what we told you, its process was completed. Now, we will talk about these areas, about earthquakes later, but they are very dangerous. Because whatever earthquakes will come in this, they will not come from the depth. We say that the depth is 700 meters, which goes up to 700 meters, which is called very deep earthquakes. But what will be considered here, that will be your shallow earthquakes. And one more thing is that we have the continental plate, which is partly subducted from the collision of both, and is subducted here. So, the crust here, the crust is the thickest, and if you come close, it goes up to 70 kilometers. Its thickness is very high. And this is also a point that the thickest crust in the world is inside the Himalayas. If we want to see it totally, how it happened, then it has been explained that India was first in the south of the equator, then slowly it moved to the north, north-west, north-east, and after that it collided with the Eurasian plate or the Tibetan plate. And before that, as we said, there was subduction and this happened. So, it was found that the breaking that took place in the south, in the beginning, we told you how the plates were together, and that land mass was also called Panjia and Gondwana land. And after that, it started moving slowly. So, initially it was found that about 80 million years ago, India was located around 6500 to 7000 kilometers south of the Asian continent. So, it was around 6500 to 7000 kilometers south and it started moving towards the north. This is the resultant vector that tells us where it started moving. So, when it initially started moving, when it was 6500 to 7000 kilometers away, then the rate of movement was considered to be around 9 meters per century. So, in 100 years, it moves around 9 meters. But when it collided about 40 to 50 million years ago, then its movement was almost half. So, we can say that it decreased by 4.5 meters per year. So, why did it decrease? The reason for this decrease was also that when it collided with the Eurasian plate or the Tibetan plate, then its motion slowed down. But this is the reason why the growth of the Himalayas increased due to the collision with the Eurasian plate. So, if we take the total length from east to west, then it is about 2900 kilometers. So, these are some more pictures that show how India collided with it. Now, we will discuss this in the next lecture. So, a model has been shown on this side, how this collision would have happened. So, this was the first stage, when it collided with the Asian or Eurasian plate, if you call it the Tibetan plate. So, when the Indian plate collided with it, then some cracks started forming like this, we call it fault lines. And as it moved further in the second stage, then some portion of it broke and started moving towards the east. So, this portion is of China. So, the plate of China has started moving towards the east. And this can be seen in the GPS measurements. So, there are many such faults in the current situation. And if you look at the picture on the left-hand side, then we have marked this whole thing, this is the subduction zone. And here, because this is a subduction zone, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults. So, if you look at the picture on the left-hand side, then there are many faults. So, if you look at the picture on the right-hand side, then there are many faults.