Geography · Year 7 · The Restless Earth: Geomorphology · Autumn Term

Earth's Internal Structure

Investigating the Earth's internal layers and their composition.

• National Curriculum Attainment Targets
• KS3: Geography - Physical Processes: Geological Processes

About This Topic

Plate tectonics is the 'grand unifying theory' of geography, explaining why our planet looks the way it does. This topic explores the Earth's internal structure, from the solid inner core to the fractured lithosphere. Students investigate the evidence for continental drift, such as fossil records and the 'jigsaw fit' of continents, and learn how convection currents in the mantle drive the movement of tectonic plates. This aligns with the KS3 National Curriculum focus on geological processes and the physical changes to the Earth's surface.

Understanding plate boundaries is key to predicting where natural hazards occur. By studying constructive, destructive, and conservative boundaries, students see how the Earth is constantly being recycled and reshaped. This topic benefits from active learning because the scales involved are so vast. Using simulations and physical models allows students to see processes that normally take millions of years happen in seconds, making the mechanics of the Earth much clearer.

Key Questions

1. Explain the scientific evidence used to infer Earth's internal structure.
2. Compare the properties of the Earth's crust, mantle, and core.
3. Analyze how the Earth's internal heat drives geological processes.

Learning Objectives

• Compare the physical properties (density, state, temperature) of the Earth's crust, mantle, and core.
• Explain the primary sources of Earth's internal heat and how they drive convection currents.
• Analyze seismic wave data to infer the composition and state of Earth's internal layers.
• Identify the main chemical compositions of the Earth's crust, mantle, and core.

Before You Start

Rocks and the Rock Cycle

Why: Students should have a basic understanding of different rock types and how they form to grasp the composition of the Earth's crust and mantle.

Heat Transfer

Why: Understanding conduction, convection, and radiation is essential for explaining how heat moves within the Earth's mantle and drives geological processes.

Key Vocabulary

Lithosphere	The rigid outer part of the Earth, consisting of the crust and upper mantle, which is broken into tectonic plates.
Asthenosphere	The highly viscous, mechanically weak and ductile region of the upper mantle of Earth, directly below the lithosphere.
Convection Currents	The movement of heat energy through fluids (like the semi-molten rock in the mantle) by the circulation of currents, which are heated from below and cooled from above.
Seismic Waves	Waves of energy that travel through Earth's layers, generated by earthquakes or explosions, which provide data about the planet's interior.
Mohorovičić Discontinuity	The boundary between the Earth's crust and the mantle, identified by a change in seismic wave velocity.

Watch Out for These Misconceptions

Common Misconception

Thinking that tectonic plates float on a liquid ocean of lava.

What to Teach Instead

The mantle is actually solid but 'plastic', meaning it can flow very slowly over time. Using a 'silly putty' demonstration helps students understand how a solid can flow. Peer discussion can then clarify that plates move due to convection currents, not by floating like boats on water.

Common Misconception

Believing that plates only move during earthquakes.

What to Teach Instead

Plates are moving constantly at about the same speed your fingernails grow. Earthquakes only happen when they get stuck and then suddenly release. A simple 'friction' experiment with sandpaper can show how constant pressure leads to sudden, jerky movements, correcting the idea of intermittent motion.

Active Learning Ideas

Simulation Game: The Snack Tectonics Lab

Using biscuits to represent the crust and jam or cream to represent the mantle, students simulate different plate boundaries. They pull the biscuits apart (constructive), push them together (destructive), and slide them past each other (conservative). They must record the 'landforms' created by each movement.

45 min·Pairs

Inquiry Circle: Evidence for Pangaea

Groups are given a 'jigsaw' of the current continents but with added clues like matching fossil types and mountain ranges. They must work together to reconstruct the supercontinent of Pangaea, explaining their reasoning based on the evidence provided. This mirrors the work of early geologists like Alfred Wegener.

40 min·Small Groups

Peer Teaching: Boundary Experts

The class is split into three groups: Constructive, Destructive, and Conservative experts. Each group creates a 2-minute 'news report' explaining what happens at their boundary, what landforms are created, and where in the world it can be found. They then present to the rest of the class.

50 min·Small Groups

Real-World Connections

• Geophysicists use seismic data from global earthquake networks, like the Incorporated Research Institutions for Seismology (IRIS), to map the Earth's interior and understand mantle plume activity beneath regions like Yellowstone.
• Volcanologists study the composition of magma erupted from volcanoes, such as Mount Etna in Italy, to infer the processes occurring within the Earth's mantle and crust.

Assessment Ideas

Quick Check

Present students with a diagram of Earth's internal layers. Ask them to label the crust, mantle, outer core, and inner core. Then, ask them to write one key characteristic for each layer (e.g., solid, liquid, hottest, thinnest).

Discussion Prompt

Pose the question: 'If we could drill a hole to the Earth's center, what challenges would scientists face, and what tools would they need?' Facilitate a class discussion focusing on temperature, pressure, and the state of matter.

Exit Ticket

Students write down two pieces of evidence scientists use to understand Earth's internal structure and one way internal heat influences surface geology.

Frequently Asked Questions

What are the four layers of the Earth?

The Earth is made of the crust (the thin outer layer we live on), the mantle (a thick, semi-solid layer), the outer core (liquid metal), and the inner core (a solid ball of iron and nickel). Each layer has different properties that influence tectonic activity.

How do tectonic plates move?

Plates move because of convection currents in the mantle. Heat from the core causes the mantle to rise, move sideways, and then cool and sink. This circular motion acts like a conveyor belt, slowly dragging the tectonic plates above it in different directions.

How can active learning help students understand plate tectonics?

Active learning helps students visualise processes that are otherwise invisible. By using physical models like 'Snack Tectonics' or jigsaw puzzles of continents, students can see the cause and effect of plate movements. These hands on activities make the abstract concepts of subduction and sea floor spreading tangible, leading to better retention than just looking at diagrams in a book.

What is the difference between oceanic and continental crust?

Oceanic crust is thinner, denser, and made mostly of basalt. Continental crust is thicker, less dense, and made mostly of granite. Because it is denser, oceanic crust will always sink (subduct) beneath continental crust when they collide.