what is WEATHERING? - Mechanical weathering and chemical weathering explained

Summary

In this insightful video by Meneer Coolwijk Aardrijkskunde, the concept of weathering and its impact on landscapes is thoroughly explored. The video begins by discussing the formation of mountains and the differences between young and old mountains. The focus then shifts to weathering, an essential exogenic force that breaks down rocks due to various environmental factors. The video delves into two types of weathering: mechanical and chemical. Mechanical weathering involves physical forces like ice expansion, temperature fluctuations, and plant roots, while chemical weathering involves a reaction between rock, oxygen, and moisture. The video explains these processes in detail, highlighting how they uniquely affect different rock types, especially sedimentary rocks like limestone.

Highlights

• Weathering involves breaking down rocks due to environmental forces. 🌧️
• Mechanical weathering includes ice expansion, temperature changes, and plant roots. 🌱
• Chemical weathering involves a reaction with water, oxygen, and certain rocks. ⚙️
• Limestone is particularly susceptible to chemical weathering. 🧱
• Different climates influence the rate and occurrence of weathering processes. 🌦️

Key Takeaways

• Weathering is a crucial exogenic force shaping our landscapes. 🌍
• Mechanical weathering breaks rocks without changing their composition. 🔨
• Chemical weathering changes rock composition through chemical reactions. ⚗️
• Ice expansion, temperature changes, and plant roots are key mechanical weathering agents. ❄️🌡️🌿
• Moisture and oxygen cause chemical weathering, especially in limestone. 💧💨
• Limestone landscapes are uniquely shaped by prolonged chemical weathering. 🏞️

Overview

The video kicks off with a look at how mountains come to be, diving into the fascinating world of sedimentary and igneous rocks. It unpacks how fossils make their way to mountain tops, contrasting the sharp relief of young mountains with the smoother profiles of their older counterparts. This sets the stage for understanding how forces like weathering shape our landscapes.

Diving into the heart of weathering, the video explores both mechanical and chemical aspects. Mechanical weathering is all about the physical breakdown of rocks via ice, heat, and flora. Fascinatingly, it turns out that water's expansion when it freezes is a formidable force, capable of prying open rock cracks. Likewise, temperature swings and resilient plant roots contribute to rock fracturing.

Chemical weathering is presented as a more transformative process, where the composition of rock changes due to reactions with water and oxygen. This process is particularly intense in sedimentary rocks like limestone, which contain fossilized seashells and calcium. The acidity from these reactions can dissolve significant portions of these landscapes, giving rise to unique geological formations.

Chapters

• 00:00 - 00:30: Introduction to Landscapes In this introductory chapter about landscapes, the transcript covers the formation of mountains, highlighting the presence of both sedimentary and igneous rocks. It explains how fossils found in sedimentary rocks can be located at mountain summits. Additionally, it differentiates between young and old mountains based on certain characteristics.
• 00:30 - 01:00: Forces Shaping Landscapes The chapter discusses the various forces that shape landscapes, focusing on exogenic forces, which are external factors that influence terrain features. It contrasts young mountains and old mountains, describing how young mountains are steep and tall with significant relief, whereas old mountains are smoother and more gradual. The differences in appearance between young and old mountains result from these exogenic forces acting over time.
• 01:00 - 01:30: Introduction to Weathering Weathering is the process of breaking down rocks due to the influence of weather and biological factors like flora. It emphasizes how weather conditions such as rain and temperature contribute to rock decomposition. Additionally, plants and trees in the surrounding environment also play a role in weathering. The chapter poses questions about the various methods and locations where weathering occurs, prompting further exploration of these topics.
• 01:30 - 02:00: Types of Weathering In the chapter titled 'Types of Weathering,' two primary types of weathering are introduced: mechanical weathering and chemical weathering. The chapter begins with an explanation of the fundamental differences between these two types of weathering. Following this, the chapter explores the various forms of mechanical weathering, detailing the processes and factors involved. Finally, it delves into the workings of chemical weathering, providing examples to illustrate how it operates.
• 02:00 - 04:30: Mechanical Weathering - Definition and Types Mechanical weathering refers to the process by which rocks break down into smaller pieces without any change in their chemical composition. This is different from chemical weathering, where the rock's molecules change due to reactions with oxygen and moisture. Mechanical weathering can occur in three primary ways, with the first being caused by water.
• 04:30 - 07:00: Chemical Weathering - Definition and Process Chemical weathering involves the breakdown of rocks through chemical reactions, often facilitated by water. A key process in chemical weathering is the expansion of water when it freezes, which can cause mechanical weathering as well. This process includes water seeping into cracks in rocks and expanding upon freezing, ultimately breaking the rock apart. This mechanism illustrates the important and unique properties of water, particularly its ability to expand when it turns into ice, which can lead to significant geological changes over time.
• 07:00 - 09:00: Comparison and Summary of Weathering This chapter describes the process of weathering, focusing on the transformation and effects of water. It begins with water turning into ice, which then expands as it freezes. This expansion has the capability to crack rocks open. The cycle continues as the ice melts back into water, and the process of freezing and expanding repeats. Over time, this repetition causes more significant cracks in the rock, demonstrating the persistent impact of weathering.

what is WEATHERING? - Mechanical weathering and chemical weathering explained Transcription

• 00:00 - 00:30 hello and welcome back to another Geo explaining video and today we will continue with chapter 1 landscapes in the first paragraph you have learned how mountains are formed How Mountains have both sedimentary rocks and igneous rocks and how fossils which are in the sedimentary rocks end up on top of the mountains and you also learned how young mountains are different than old mountains by how
• 00:30 - 01:00 they look today we will look into the forces that shape the landscape remember how young mountains look very different more Steep and Tall compared to Old mountains which are more smooth and gradual these young mountains have way more relief differences in height compared to the Old Mountain this is because of the outside forces the geographical term for these outside forces that shape the landscape is exogenic forces one of these exogenic
• 01:00 - 01:30 forces is called weathering weathering is the breaking down of rocks under the influence of weather and Flora meaning that because of the weather how much it's raining or the temperature rocks can break down but also because of the plants around us and the trees rocks break down but in which ways does weathering happen and where can you find these different types of weathering try to answer these questions so we can
• 01:30 - 02:00 discuss them in class you need to know two types of weathering first there is mechanical weathering and on the other hand there is chemical weathering I will first explain to you the difference between chemical and mechanical weathering then I will go over the different types of mechanical weathering that we need to know and then I will also explain how chemical weathering works and give an example of each so first what is the difference between chemical weathering and mechanical weathering with
• 02:00 - 02:30 mechanical weathering the rocks break down but the composition of the rock stays the same it does not change but with chemical weathering the composition of the rock changes so the molecules change so there is some sort of chemical reaction between the rock the oxygen and the moisture which breaks down the rock now in which three ways does mechanical weathering happen the first way that mechanical weathering is happening is caused by water that is
• 02:30 - 03:00 freezing so you can kind of Imagine where this type of weathering takes place one very important thing to know is that water is very special not because it tastes so good but because when it solidifies and turns into ice it expands meaning it gets a little bit bigger when it turns into ice and the mechanical weathering goes as follows step one the water will fill into a crack of a rock step two the water in the crack of The Rock will turn
• 03:00 - 03:30 from liquid into solid turning into ice and step three as it turns into ice it expands the expanding ice is so strong that it can crack the rock a little bit more open and step 4 the ice melts and it turns into water again and the last step step 5 is to repeat step two three and four over and over again and eventually crack
• 03:30 - 04:00 the rock breaks and this is how mechanical weathering with frozen water happens let's move on to the second type of mechanical weathering the rock crumbles and breaks because of big temperature differences for example in the desert it can be as warm as 40 degrees celsius during the day but during the night it cools down to -3 when things get warm they expand and
• 04:00 - 04:30 when they get cold they shrink a little bit this is not always visible to our eyes but this does happen on a molecular level and when this happens over and over and over again at some point the rock can't handle this growing and shrinking anymore and it just cracks it crumbles into many pieces or just splits into and this is how mechanical weathering with big temperature differences can happen the third and last type of mechanical
• 04:30 - 05:00 weathering that you need to know is caused by Flora so plants and treats you might not think of it when you look at plants and trees but they are actually quite strong so strong even that it can break rocks this is how paper beats rocks in rock paper scissors when a plant or a tree root grows into a tiny crack of a rock it can slowly grow and get bigger and stronger and push the Rock from inside out eventually this pushing will become so strong the root of the plant or tree will become so
• 05:00 - 05:30 strong that it just cracks The Rock open so this is how Flora plants and trees cause mechanical weathering now we switch over from mechanical weathering to chemical weathering now chemical weathering does not happen from strength of ice or plant roots or big temperature differences chemical weathering happens with a chemical reaction and for this chemical reaction we need a couple ingredients first we need a soft type of
• 05:30 - 06:00 rock second we need oxygen and third we need moisture so it needs to be wet chemical weathering happens when rain water and oxygen react on a certain material and on certain rocks which causes the water to be more acidic this reaction happens faster in climates that are warmer and more moist so you can kind of guess where in the world chemical weathering will happen faster
• 06:00 - 06:30 the chemical process that takes place with the water the oxygen and The Rock cause the rock to dissolve and this is how chemical weathering changes or breaks down the rock it just dissolves The Rock but not every type of rock is as easily affected by chemical weathering we know about igneous rock you know the type of rock that is formed by solidified magma this rock is very hard and very strong so it is not as much affected by
• 06:30 - 07:00 chemical weathering but sedimentary rock especially those with loads and loads of fossils in them experience a lot of chemical weathering sedimentary rocks filled with fossils have a lot of calcium in them and when there are so many fossils of sea creatures such as Plankton and shell animals the type of sedimentary rock that is formed is called Limestone this type of rock limestone is relatively soft and is very
• 07:00 - 07:30 weak against the process of chemical weathering because calcium reacts quicker to oxygen and moist so when you have a landscape which consists of a lot of limestone this type of sedimentary rock the rain and oxygen will have a very heavy chemical reaction with the Limestone it will dissolve large parts of the landscape this type of landscape made from Limestone where chemical weathering has been happening for many
• 07:30 - 08:00 many years is very unique and this type of landscape is called a cast launch hop so chemical weathering is very different compared to mechanical weathering with mechanical weathering you really have the process of the temperature or the water or the Flora that breaks The Rock and with chemical weathering you really need a chemical reaction between oxygen moisture so water and a type of rock a
• 08:00 - 08:30 type of material so to summarize everything that we've learned you now know what weathering is in which three-ways mechanical weathering can happen how chemical weathering happens what the difference is between igneous rock and sedimentary rock and especially limestone on chemical weathering and how Landscapes with Limestone are much affected by this chemical weathering and caused the creation of a
• 08:30 - 09:00 cutlance hop and overall just in general our climates have an influence on these types of weathering whether they go quicker or if they can happen or not thank you guys for watching I hope you learned something new today and I'll see you in the next one goodbye