Intro Quiz: How do aretes and pyramidal peaks form?

Video: How do aretes and pyramidal peaks form?

﻿Hello Geographer, my name is Miss Thiel and I'm really pleased to have you here for this lesson. For this lesson you will need to have the following equipment: pen, pencil, ruler and something to write on. If you need time to go gather your equipment then pause the video now. Excellent, you've got the equipment you need for this lesson, one final thing make sure you clear away any distractions from around you and ideally, if you cam go find somewhere quiet where you can complete the work for this lesson. Okay, I'm ready when you are, lets go. This is lesson three in the glaciation unit of work. Our title is "How do arêtes and pyramidal peaks form?" I'd like you to make sure that you have this title written down on your piece of paper, and underlined with a ruler. So if you need time to do this, pause the video now. Excellent, you've got your title written down and it's underlined with a ruler, let's now begin the lesson. Arêtes and pyramidal peaks are both examples of Glacial landforms. That means that they are natural, recognisable features on the land, formed by the action of glaciers. We're going to start with the characteristics of both arêtes and pyramidal peaks. Characteristics is another word for features, so what do we see when we're looking at an arête or a pyramidal peak. Here we have two photographs of arêtes. What do you see when you look at these photographs? How would you describe an arête to somebody who had their eyes shut? Think about it's shape, colour, or texture. Now, we have two photographs of pyramidal peaks. Again, what do you see? How would you describe a pyramidal peak to somebody who had their eyes shut? Is it similar to something that you have seen before? The characteristics of arêtes are that they are a narrow ridge, shown here, with the white dashed line. They have steep sides, either side of this ridge. Not something that you could easily walk down or up. If we look further down these slopes, we can see hollowed out depressions either side of the arête. There is a lake on the left hand side of this arête, here. And what about the characteristics of pyramidal peaks? They are steep pointed peaks, with a similar shape to the pyramids built by the Egyptians. We can see arêtes, or narrow ridges, running up towards the peak of the pyramidal peak, shown here with the blue dashed lines. Finally, we can also see a hollowed out depression just here. This hollowed out depression is called a corrie, and it was also formed by the actions of glaciers. We looked at how corries form in lesson two of this unit of work. But lets take a moment to remind ourselves about how corries form. Corries are hollowed out depressions or gouges in the side of a mountain, and they form when a glacier erodes or wears away the rock through processes such as abrasion and plucking. We looked at the definitions of these processes abrasion and plucking in lesson two of this unit. Remember, abrasion is the scraping of rocks along the ground, wearing it down. And plucking is where rocks are pulled from the ground as water freezes to them. If you need to remind yourself of these processes, and perhaps write down their definitions, then pause the video now. Let's have a quick check of our knowledge. Which two are characteristics of arêtes? Pause the video now so you have time to read each of the options. How did you do? Tell me which options you think are characteristics of arêtes, go! Excellent, well done! Option three and Option four are the two characteristics of arêtes. They are narrow ridges with steep slopes leading to hollowed out depressions in the side. Well done. Next up, which are the correct locations for the corries in the photograph. Option 1: A and B or, Option 2: B and C. Five seconds too think about it. And tell me which option, excellent, A and B are where our corries are. Remember, your corries are the hollowed out depressions in the side of a mountain created by the erosive power of glaciers. And finally, which two are true for pyramidal peaks? So that you have time to read each of the four options, pause the video now. Excellent, and tell me which two options are true. Well Done, Option 2 and Option 4 are true. Option 1 is false because pyramidal peaks do not have gentle slopes, they have steep slopes and Option 3 is false, because we know that we see arêtes or narrow ridges running up towards the peak of the pyramidal peak. Excellent work. For this next task, you are going to be drawing the sketch at the same time as I am drawing the sketch. After we finish the sketch you are then going to have to add these labels here, in pink, to your sketch. Where there is a number in the brackets, that refers to how many times you should have that label on your sketch. Final important thing, you're going to have to make sure you have a pencil and a ruler to do this sketch, so if you need time to grab your pencil and ruler then pause the video now. Excellent, you ready? Lets get sketching. Start your sketch off by having a box drawn with a pencil and ruler that is around about 10-12 centimetres across, and 10-12 centimetres down. So that you have time to do that, pause the video now. Excellent, so now lets start with our sketch. Middle of the bottom of the box I'm going to draw a line that's around about 1 centimetre high. To the left but slightly higher than this line, we're going to draw another one. And then to the right, but slightly higher than this line, we're going to draw another one. Next we're going to join up these lines with straight lines, so from this point to this point we're going to draw a straight line. And then from this point to this point, we're going to draw a straight line. Now, from this point here to this point here, we're going to draw a line that is curved. So it goes down and then back up as it gets closer to that point. And then the same again here it goes down and then back up. Next we're going to draw the outer limit of the sketch, so from this point here, you're going to draw a curved line to the top. And then from that top point you just draw and we're going to draw a curved line down to here. Then to give this diagram some depth we're going to go from the peak draw a wiggly line down to this point there. After that go back to the peak and then starting just underneath the peak draw another slightly curved line that stops halfway. Repeat in the other triangle shaped area. And then to give the effect that these sides here are quite steep we're going to draw a series of dash lines, it doesn't matter how many you do. Just like that. And there you have it, super simple diagram but should be fit for purpose. You'll see that I have left lots of space up here and I've done that for two reasons; One, so I've got space for adding labels to my diagram, just in case I didn't have any space on the sides of the diagram, which I don't. And two, because this needs to have a title. So over to you now, add those labels to your diagram and add a title, off you go. How did you get on with your sketch. I want you to now check. Compare your sketch to mine that's on the right hand side of the screen. Have you got the correct labelling? Are your labels pointing directly to the landform that you are labelling? Are your arrows drawn with a ruler? And finally, have you got a detailed title? If you need time to improve your sketch, then pause the video now. Next, we're going to have a look at how arêtes and pyramidal peaks form. To do that we get to look at some really cool satellite imagery. Those are images that are taken by satellites in space. Lets start with how do arêtes form. This satellite image is of an arêtes that can be found in the lake district in the North West of the United Kingdom. Can you see the arêtes in this image? Run your finger along it. Well spotted, the arête is this narrow ridge just here, shown with the white dashed line. How we ended up with forming this arête is because of what used to be found in these two hollowed out depressions right here, and here. These hollowed out depressions are corries, which means back when the land was covered in ice here, two glaciers sat in these depressions. Lets rewind time back even further to see exactly how this arête here was formed. Firstly, glaciers need to form in two adjacent valleys, that means they're next to each other, and they're separated by a mountain. Next, the erosive power of these glaciers, the processes of abrasion and plucking to be specific, result in the formation of two corries, those are our hollowed out depressions. As erosion continues, the back walls of the corries get closer together. The back walls are now shown on the diagram with the pink dashed line. Finally, this leaves us with a steep, knife edged ridge called an arête. Next lets have a look at how pyramidal peaks form. Again, we're going to look at satellite images to do this. At this pink pin drop, we can see a pyramidal peak. It is the summit of a mountain, called Mount Snowdon, found in North Wales. We can see running away from the peak a narrow ridge, or an arête, just here, and also here, and finally, also here. So what do these arêtes look like from side on? We can see here the steep sides running either side of these arêtes that lead up to the pyramidal peak. We definitely couldn't easily walk up or down these. Next lets take a look at what can be found in between the arêtes. We can see a corrie here, another corrie here, and a third corrie here. If we now have a look around this pyramidal peak we can really clearly see these large hollowed out depressions of the three corries around the pyramidal peak. So already lets think about how the formation of a pyramidal peak is different from an arête. To from a pyramidal peak we need to have three or more glaciers back to back, separated by different mountain valleys. This is different from an arête which only requires two corries, or glaciers. Next the erosive power of these three or more glaciers, again, abrasion or plucking results in the formation of corries. Consequently, erosion makes these back walls, these pink dash lines on our diagram to get closer and closer together. And instead this time, this leaves us with a steep sided pointed peak called a pyramidal peak. So tell me how many glaciers are required to form an arête? Show me with your fingers. Well done, we only require two glaciers forming back to back to form an arête. We can see that in this picture just here, where we can see there's one, and the two in the corries where there used to be glaciers back to back. Next, how many glaciers are required to form a pyramidal peak? Show me with your fingers. Excellent, well done. Three or more. So we need to have at least three glaciers back to back to from a pyramidal peak. We an see that in this satellite image here we've got one, two, three corries back to back where there used to be glaciers. And finally, which two are processes which form arêtes and pyramidal peaks? Five seconds to think. And tell me what are those processes? Good, abrasion and plucking, they are both erosion processes that form arêtes and pyramidal peaks. Excellent work. Now it's nearly time for you to have a go at the final main task for this lesson. For this main task I want you to imagine that you are completing geography field work in the area surrounding Mount Snowdon in North Wales. Remember, this is the area we looked at the satellite imagery for. For this field work you are going to walk along this route shown here with the white dash line. With that in mind, you will be answering this question here: Explain how glaciers have shaped the land at stop B. When you get round to writing your answer to this question, you will have this success criteria: Identify the landform at stop B. Describe the key characteristics of the landform. Explain the processes that formed the landform at B. And, use sequence connectives. Before you do that, I'm going to show you how to answer this question but for the landform found at stop A, not stop B. So start of by telling me what landform can we see at stop A? Good, we can see an arête at stop A. We can see that if we were walking along this route we would be walking on a narrow ridge, an arête. Let's look at how I would answer this question for stop A then. At stop A I can see a glacial landform called an arête. An arête is a steep, knife edge ridge. Firstly, we need twp glaciers to form in adjacent valleys. These glaciers will erode the rock through abrasion and plucking. Eventually, this forms two hollowed out depressions called corries. Over time, as more erosion happens, the back walls of the corries get closer, leaving a steep ridge called an arête. Let's quickly remind ourselves of what the success criteria was for this answer, so we can see if this answer was good enough. Our success criteria said that we need to identify the landform. We need to describe it's characteristics. Explain the processes that form it, and use sequence words. Lets see where I have done all of this. Now you can see I have gone through my answer and highlighted my process words in pink, my sequence words in purple, and I've added a tick next to where I've identified it, and described the key characteristics. You will be doing exactly this but for the landform found at location B. Okay, so over to you now, time to answer the question: "How have glaciers shaped the land at stop B?" Remember we just looked at stop A which was an arête, so have a think about what landform we might see at B. What was the other landform we looked at in this lesson? Refer back to your success criteria to help you write this answer. I'm sure you'll do a fantastic job. So that you have time to write your answer pause the video now. Well done for working really hard on that last question. Before I show you the answer to the question, tell me, what landform do you think you'd see at stop B? Yes, well done, a pyramidal peak. We would see a pyramidal peak at stop B. Before I show you the answer to this question, I want you to make sure you're disciplined and you take time to read through my answer and of course check it and compare it with your own. Make sure that your answer has all the sections of my answer that are highlighted in pink, purple or have a tick next to them. If you need time to improve your answer then make sure you pause the video to do exactly that. Okay, here goes. And that brings us to the end of this lesson, so well done for all your fantastic learning that you have achieved in this lesson make sure you now go and complete the exit quiz so that you can test that learning. In this lesson we learned how the two glacial landforms, arêtes and pyramidal peaks, form. In this next lesson in this unit of work we are going to have a look at another glacial landform, a glacial through, and see how they form. See you next time.

Exit Quiz: How do aretes and pyramidal peaks form?

Completed: How do aretes and pyramidal peaks form?

In this lesson we will learn about the characteristics and formation of the glacial landforms arêtes and pyramidal peaks.

Geography

How do aretes and pyramidal peaks form?

Introductory Quiz

Video

Final Quiz

Lesson Complete