External (Exogenic) Processes - 4.2 | Chapter: Physical Geography | IB MYP Grade 10 – Individuals & Societies (Geography)
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4.2 - External (Exogenic) Processes

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Interactive Audio Lesson

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Weathering

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0:00
Teacher
Teacher

Today we're delving into weathering, the first external process. What do we know about it?

Student 1
Student 1

Isn't weathering when rocks break down?

Teacher
Teacher

Exactly! Weathering can be physical or chemical. Who can give examples of each?

Student 2
Student 2

Physical would be like freeze-thaw cycles where water gets in cracks and expands.

Student 3
Student 3

Chemical could be rust or the dissolution of limestone in acidic water.

Teacher
Teacher

Great examples! And remember, weathering doesn't move material, but it prepares it for erosion. Let's take this knowledge further!

Erosion

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0:00
Teacher
Teacher

Now that we know how materials break down, let's talk about erosion. How does it differ from weathering?

Student 4
Student 4

Erosion actually moves the materials away, right?

Teacher
Teacher

Yes! It's the transportation of those weathered materials. Can anyone name the agents of erosion?

Student 1
Student 1

Water, wind, ice, and even gravity!

Teacher
Teacher

Perfect! And think about how powerful water can be over time. Let's discuss how erosion shapes landforms.

Deposition

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0:00
Teacher
Teacher

Finally, we can't forget about deposition! What happens during the deposition process?

Student 3
Student 3

That's when the materials that were transported are laid down somewhere else!

Teacher
Teacher

Exactly! This can lead to the formation of new landforms. Can anyone give an example of a landform created by deposition?

Student 2
Student 2

Deltas at the mouth of rivers, where sediment collects!

Teacher
Teacher

Right! So remember, weathering breaks down materials, erosion transports them, and deposition drops them off.

Introduction & Overview

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Quick Overview

External processes such as weathering, erosion, and deposition shape the Earth's landforms and landscapes.

Standard

This section details external (exogenic) processes, emphasizing how weathering, erosion, and deposition modify landforms. By understanding these processes, students can appreciate the dynamic nature of landscapes and their significance to human activities.

Detailed

External (Exogenic) Processes

External processes, also known as exogenic processes, encompass the physical and chemical processes that occur on the Earth’s surface, leading to the transformation of landforms. This section intricately explores three major exogenic processes:

  1. Weathering - This is the breakdown of rocks into smaller particles through biological, chemical, or physical means. There are two main types: physical weathering, which breaks rocks without altering their chemical composition, and chemical weathering, which involves changes in the minerals that comprise the rocks.
  2. Erosion - This refers to the removal and transportation of weathered rocks and soil from one location to another. Various agents such as water, wind, and ice contribute to erosion, reshaping the landscape significantly over time.
  3. Deposition - After erosion, materials are laid down or deposited in new locations, leading to changes in topography like the formation of deltas and riverbanks.

The interplay of these processes ultimately shapes various landforms including mountains, plains, plateaus, valleys, and deltas, which are vital for understanding both the natural environment and the impact human activities have on it.

Audio Book

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Introduction to External Processes

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External (Exogenic) Processes:
• Weathering – breakdown of rocks
• Erosion – removal and transport of materials
• Deposition – laying down of sediment

Detailed Explanation

External processes are those that occur at or near the Earth's surface, shaping the land over time. They include:
1. Weathering: This is the process through which rocks are broken down into smaller particles. Weathering can happen physically (like ice freezing and thawing in cracks of rocks) or chemically (when rainwater reacts with minerals in the rocks).

  1. Erosion: Once rocks are broken down through weathering, they can be carried away by natural forces. Erosion refers to the movement of soil and rock from one place to another, typically by water, wind, or ice.
  2. Deposition: After materials have been eroded, they are eventually dropped or deposited in a new location. For example, rivers carry sediments and, when they slow down, these sediments settle and form new landforms like deltas.

Examples & Analogies

Think of a sandy beach. Over time, waves crash against rocks, breaking them down (weathering). The sand is then picked up by the waves and carried along the shore until it settles in quieter areas (erosion and deposition). Just like building a sandcastle, where the sand you gather is weathered away from the cliffs and then deposited in your castle's base.

Types of External Processes

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Types of External Processes that Shape Landforms:
• Weathering
• Erosion
• Deposition

Detailed Explanation

External processes encompass three primary types that work together to shape landforms:
1. Weathering: This is the foundational step where rocks are physically or chemically broken down into smaller particles. Factors like temperature changes, water, and biological activity (like roots growing into rocks) contribute to this process.

  1. Erosion: After weathering, the small particles need to be moved. Erosion is the process where these weathered materials are carried away by agents like water (rivers, rain), wind, or ice (glaciers). This process can create valleys or canyons over a long period.
  2. Deposition: Finally, the eroded materials are deposited. When rivers slow down, they drop their load of sediment, creating features such as riverbanks, deltas, or sandbars. This accumulation plays a vital role in reshaping the Earth’s surface and can create fertile land for agriculture.

Examples & Analogies

Imagine a river. As it flows through the landscape, it cuts through rock to create a valley (weathering). It carries away pieces of that rock as it flows (erosion), and when the river reaches a lake or the ocean where it slows down, it drops off the sediment, creating a delta where new life can flourish (deposition).

Definitions & Key Concepts

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Key Concepts

  • Weathering: The breakdown of rocks due to physical and chemical processes.

  • Erosion: The transport of weathered materials by natural forces.

  • Deposition: The accumulation of eroded materials in a new location.

Examples & Real-Life Applications

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Examples

  • An example of physical weathering is freeze-thaw action where water expands in the cracks of rocks, causing them to break apart.

  • A delta is formed at the river mouth where sediment carried by the river is deposited.

Memory Aids

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🎵 Rhymes Time

  • Weathering's breaking, Erosion's moving, Deposition's laying down, that's the groove.

📖 Fascinating Stories

  • Imagine a mountain rock, weathering under the sun and rain, breaks apart; water carries it to the river where it’s deposited at the delta, forming new land.

🧠 Other Memory Gems

  • Remember WED: Weathering breaks down, Erosion takes away, Deposition lays down.

🎯 Super Acronyms

WED (Weathering, Erosion, Deposition) - Think of it as the process that creates new landscapes!

Flash Cards

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Glossary of Terms

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  • Term: Weathering

    Definition:

    The process of breaking down rocks and minerals into smaller fragments.

  • Term: Erosion

    Definition:

    The removal and transport of weathered rock and soil from one location to another.

  • Term: Deposition

    Definition:

    The laying down of material that has been eroded.