Intro Quiz: How do caverns form in limestone areas?

Video: How do caverns form in limestone areas?

﻿Hello geographer, My name is Ms. Thiel and I'm really excited to have you here for this lesson. As we get to that about my favourite landform, a cavern. 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 get this equipment, then pause the video now. Excellent. You've got the equipment you need for this lesson. Finally, I want you to clear away any distractions from around you and ideally go find a quiet place where you can complete the work for this lesson. Okay. I'm ready when you are. Let's go! This is lesson eight in the geology of the UK unit of work. Our title is how do caverns form in limestone areas? I'd like you to make sure you've got this title written down on your piece of paper, and on the line with a ruler. So if you need time to do this, then pause the video now. Great. You got your title written down. Let's now begin the lesson. Let's start by making sure we know what limestone is. Limestone is an example of a sedimentary rock that's made of calcium carbonate, and it forms in shallow seas. The calcium carbonate comes from the remains of the skeletons of shells and other sea creatures, such as starfish. And sometimes if you look closely in that limestone, you can see those shells. Limestone is a rock that can be found in the Peak District. In lesson six of this unit of work, we learned what the peak district is and where it is. The peak district is a national park found in the centre of the United Kingdom. Here, limestone is found in the White Peak area, and this is shown with the colour blue on this geological map here. This area is called White Peak because the rock limestone is a light grey to white in colour. In this limestone area of the Peak District, we can find caverns. We're now going to have a look at what the characteristics of caverns are. Characteristics is another word that means the features of something. So, what would we see if we were to look at a cavern? Here, we have a photograph of inside a cavern. So what are the characteristics of a cavern? They are found underground. They are made of discoloured grey or brown rock. We can find water on the floor of the cavern, and we can also find thin pillars that stretch from the floor to the ceiling of the cavern, as well as long deposits hanging from the ceiling or growing up from the floor. These deposits which hang from the ceiling, or grow taller from the ground of a cavern, are called stalactites and stalagmites. They are both made of calcium carbonate, the same compound that makes up limestone. Let's practise saying those words. Repeat after me. Stalactites. Good. Stalagmites. Excellent. Now, it is important that we know the difference between stalactites and stalagmites. Stalactites are thin deposits of calcium carbonate that hang from the ceiling of a cavern. They generally have very pointy tips, like an arrowhead does. Here we can see a stalactite in this diagram. Stalagmites are thin deposits of calcium carbonate that grow taller from the floor of a cavern. And they have less pointy tips compared to stalactites. Here, we can see a stalagmite in this diagram. So how can we remember the difference between stalactites and stalagmites? One way is by realising that stalagmites has a G in, a , and stalagmites grow taller from the ground. So stalagmites grow taller from the g-round. Practise saying that with me. Stalagmites grow taller from the g-round. Good, well done. We won't get our stalactites and stalagmites confused anymore. Finally, sometimes when stalagmites and stalactites meet in the middle, they form a pillar. A pillar is a continuous column of calcium carbonate, which is connected from the floor to the ceiling of a cavern. You can see this on the diagram. So, it's super important we know the difference between stalactites and stalagmites. So I want you to write down stalactite, and a description of what it is, and also stalagmite, and the description of what it is. Where do we see stalactites and stalagmites forming in the cavern? So that you have time to write down all of this information, I want you to pause the video now. So, time for a quick check of our knowledge. Which type of rock do caverns form in? Option one, granite. Option two, limestone. Option three, mudstone. Option four, sunstone. Tell me which option. Option two is correct, well done! Caverns form in the rock type limestone. Next up, which one is the correct labelling for the photograph? Option one is: A equals pillar, B equals stalactite, and C equals stalagmite. Or option two: A equals stalactite, B equals stalagmite, C equals pillar. 10 seconds to think about this. Go! Tell me which option. You are right, option one! Let's double check so we can be happy with that. A is pointing to a pillar of calcium carbonate that stretches from the floor to the ceiling of the cavern. Therefore it is a pillar. B, is that a stalactite? How can we be sure? A stalactite hangs from the ceiling, and here B is pointing to exactly that, and therefore C, stalagmite, they grow taller from the ground. So therefore is that happening at C? Yes it is, well done. Next, we're going to have a go at this task just here. Draw a labelled diagram to show the difference between stalactites, stalagmites, and pillars. For this task, you're going to need to have your pencil and your ruler ready. So if you need time to get your pencil and ruler, pause the video now. When you're ready to draw your labelled diagram of stalactites and stalagmites. Let's begin by drawing a box with a pencil and ruler that is 10 sentences across and 10 sentences down. So that you have time to do this, pause the video now. Let's begin with drawing our stalagmite. So remember we exaggerated G in stalagmites, cause it reminds us that they're on the ground. So stalagmites are on the ground. So starting on the floor of the cavern, just going to draw a wiggly line and then occasionally bring that line up, and then back down. And those are your stalagmites. But remember that your stalagmites have rounded tips compared to your stalactites. So we're not drawing them with pointy ends, we're drawing them with much rounded ends. And then this last stalagmite here I'm leaving unfinished, and we'll find out why in a minute. Then onto our stalactites, the stalactites hang from the ceiling. So at the top of our box, we're going to draw our wiggly lines that come down to form our stalactites. And they have much pointier tips compared to the stalagmites. And on this last one, I'm going to draw it connecting with that stalagmite, that I left unfinished. This is our third feature that we see in a cavern, where a stalagmite joins a stalactite. We form a pillar. We're now ready to label our diagram. So when you're labelling, make sure the head of the arrow points to what you are labelling, and you want to make sure you've got enough space around to add your label. So let's label our stalagmites first. I'm drawing my arrowhead, and it's pointing directly to a stalagmite. And then with my ruler, I draw my arrow away from the stalagmite, and next to the arrow, I'm going to write the label. So capital S. Stalagmite. Next, let's do stalactites. So again, arrow points to what you're labelling. Ruler to draw the rest of your arrow. Capital S. Stalactite. And then lastly, our third and final feature are our pillars. So, arrowhead. Next, we're going to have a look at: How do caverns form? And how do stalactites, stalagmites, and pillars form inside of them? We must first remind ourselves the caverns form in areas where we see the rock type limestone. Firstly, rainwater seeps down and along the joints and bedding planes in the limestone. Bedding planes refer to the horizontal cracks you see in the limestone, and joints refer to the vertical cracks. Eventually, the rain water stops moving downwards when it meets a different type of rock that it cannot flow through. Therefore, an underground stream forms, and flows horizontally through the limestone. As the water in the underground stream is slightly acidic, it dissolves the limestone, creating a cave. This is called chemical weathering. Eventually, a large cavern is created when the ceiling of the cave collapses due to it being unsupported. Stalactites form in a cavern when water on the ceiling of the cavern evaporates, leaving behind long, hanging deposits of calcium carbonate. Stalagmites form when water drips down onto the floor of the cavern, which builds up over time, leaving deposits of calcium carbonate. As more water drips onto the top of a stalagmite, the additional calcium carbonate makes it taller. Now that we have looked at how caverns form, I want us to have a go at this question here. The question is: explain the formation of the landform shown in the photo. To help you do this, I want you to use the sentence starters that I have provided you. If you feel like you want a little of an extra challenge, then I want you to have a go at adding an explanation on how stalactites and stalagmites form. So that you have time to write your fantastic answer to this question, using the sentence starters to help you do this, I want you to pause the video now. Well done for working really hard on that last question. Let's now have a look at an answer, so we can compare it to your own answer. In my answer, you'll see that there are words and sentences highlighted in pink and bold. These are the really important bits of the answer that I want you to check your answer has when we finished reading it. Here goes. In the photo I can see a cavern. Firstly, rainwater seeps down and along the joints and bedding planes in the limestone. An underground stream forms when the water reaches a different type of rock which it cannot flow through. Next, because the water in the stream is acidic, it dissolves the limestone. This is called chemical weathering. Over time, a large open cavern is formed. So remember, your answer has to have the information that's highlighted in pink and bold. If you need time to check your work and perhaps improve it, then pause the video now. And lastly, did you have a go at the challenge explaining how stalactites and stalagmites form? Let's have a look. Stalactites form when water on the ceiling of a cavern evaporates. This leaves behind long, hanging deposits of calcium carbonate called stalactites. Stalagmites form when water drips down onto the floor of the cavern. Over time this builds up, leaving a calcium carbonate deposit called stalagmite. As more water drips down into the top of the stalagmite, it grows taller. Again, in pink and bold we've got the really important information that we have to have when explaining how stalagmites or stalactites form. If you need time to write down this information, or check your answer and compare it to this one here, then pause the video now. Before we end the lesson, let's not forget that we know of an area that is made of limestone in the UK. This area is the Peak District. In the Peak District, we can find caverns in areas where there are limestone. For example, Treak Cliff Cavern. If you were to visit Treak Cliff Cavern, on the ground surface, it simply looks like this. However, if we were to go deeper underground inside the cavern, we can see the characteristics of a cavern as we have learned in this lesson. And so you've reached the end of this lesson. Well done for all your fantastic learning that you have achieved in this lesson. Make sure you now go complete that exit quiz, so that you can test all of that fantastic learning. In the next lesson in this unit of work, we will be looking at quarrying. That is where humans extract, or take out rocks from the ground for different purposes. We will be looking specifically at the positive and negative impacts of quarrying in the UK. See you next time!

Exit Quiz: How do caverns form in limestone areas?

Completed: How do caverns form in limestone areas?

In this lesson we will learn about how caverns form in limestone areas such as in the Peak District.

Geography

How do caverns form in limestone areas?

Introductory Quiz

Video

Final Quiz

Lesson Complete