hi guys in this video we're going to be looking at unit two for GCSE geography I'm going to be looking at the section on the UK's evolving physical landscape section or topic and I'm going to go over one of the features one of the erosional features which is cave stack arch or cave stack formation so I'm just going to talk you through this then I'm going to look a little bit different types of coastline and hopefully you'll be a bit more up-to-date with them with these processes so what we've got here is a cave arch and stack formation forms on a headland which is characteristic of a discordant coastline and we'll get to that in a second what the difference is between discordant concordant but if I just run through the formation of a cave arch stack formation on a headland then you'll be in a good position to answer it in the exam so any headland starts off with erosion both sides of the headland as the water or the waves come in and they refract around the headlands really important to use that terminology so the waves kind of come in to a more shallow area around the headland and they can refer topple over each other and they move around the headlands and they attack the sides of the headland both sides of the headland so these processes are happening on either side of the headland and we'll see what happens as they kind of merge in the middle so on either side any rock formations generally got some cracks in the size of it and through the layers of the rock etc so they are lines of weakness and those weaknesses will be exploited by the weight because the waves are often very very powerful especially in the wintertime when we get very destructive waves so it starts off with some cracks in the rock and hydraulic action and abrasion occur on those areas on either side of the coastline now it's really important when you answer an exam question that you tell the examiner what hydraulic action is or what abrasion is generally those two are the two that you need to use most because they're the two processes of erosion that are having an impact on the coastline or on the rock so hydraulic action is when air in the cracks gets pushed further in by the water of the waves pushing or breaking onto the onto the rock so and they washing and they break up the rock further or make it much much weaker then the next thing obviously waves which have got particles in them crash against the sides of the headland or the sides of any cliff and that causes the cliff sides to wear away at the base so we've got cracks forming and getting wider and wider and eventually this will form a cave so we'll get a cave forming on the on one side and a K forming on the other now eventually and that erosion will occur so much that each of the caves the two case will kind of meet in the middle and that's where our arch is form so the arch is because we've had erosion on either sides of the headland and those caves have got bigger and bigger to the extent where the two caves have met and we get this gap which is C for my nice little seagull and then the gap in the middle forms and we get an arch for me now we need to take a break for a second this way and look what's happening at the top of the cliff because this is also really important at the top of the cliff we've got lots and lots of maybe trees and plants maybe some animals up there we've got lots of rainfall maybe and we get sub-aerial processes occurring at the top of the cliff and this weakens the cliff top even further now this week another cliff top eventually allows this top section of the cliff or let's the top section of the cliff become so weak that it actually collapses so this is what's happening we've got erosion at the base of the cliff and we've got sub-aerial processes happening at the top of the cliff now you must not forget this process because it will definitely get you full marks so the arch and becomes very very very top-heavy the erosional processes the subaerial processes and happen at the top and that the top of the arch basically collapses so when the arch collapses this leaves a nice tall stack okay so that is our cave arch and stack formation now the stack over time will be eroded and I'm just gonna rub this off a little bit it's basically going to be more eroded at the base as the waves come in and hit the base so it gets eaten away at the side to the side a bit of undercut in either side of that home of that stuck and eventually that will be kind of calm top-heavy a wobble a little bit and it will fall into the sea and that will leave here as we can see a stock and that's the end process so we've generally got these four or five stages and the stack is eroded at the base like I said collapse over time and forms the stump so that is our formation of cave arch and stack on a headland now I'm just going to go over very quickly concordant coastlines and discordant coastlines because this comes up quite regularly so he discordant coastline if you remember or where the rock types run at angles to the sea not always 90 degrees but maybe more or less 90 degrees and often we get hard rock soft rock hard rock soft rock kind of next to each other and where we've got harder rock that will stay as a headland which is we've got here and the softer rock will be eroded so we get headland and bay formation so related these are the two types of features that we get on a discordant coastline and that's also quite a common question is the describe and explain the features on a discordant coastline so discordant so we know what it is and then I'm not going to go over and head in them Bay because it's quite straightforward headland sticks out because it's more resistant rock and the bay erodes because it's less resistant Rock so that's not a discord of coastline and the next type of coastline is a concordant coastline from Concord it means that the rocks are on parallel to the sea so we've got harder rock maybe at the front then softer rock then harder rock and if we remember the feature that occurs here is we can get coves for me now if we have limestone like we have down in low-earth Cove down endorsed it on the Dorset coastline that is a concordant coastline that southern facing coastline and that is a band of limestone which is quite resistant and limestone does have joints in it and has cracks in it and they are lines of weakness as we said before so those lines of weakness eventually and at some points let the sea in once the Seas got through and it's a road as a little bit behind that is much softer Rock so as soon as the wave to get through that little gap or that little line of weakness it then can kind of exploit the fact that it's now hitting softer rock and we get that Cove formation and then behind and that's softer rock and Longworth Cove we've also got a layer of chalk which is a little bit more resistant so the Cove any kind of goes a certain way back along the coastline or back into the coastline because we've got that hard bands of rock soft band of rock and a hard bands of rock behind so that those are the features or that is the feature that we can find on a concordant coastline so hopefully I've covered quite a few features and processes here for an erosional processes and features on the coastline