Plate Tectonics
Continental Drift - Boundaries - Earth's Dynamics
Plate tectonics is one of the most important ideas in Grade 10 Geography because it explains why continents move and why earthquakes, volcanoes, and fold mountains happen. This lesson starts with Wegener's continental drift theory and then shows how plate movement changes the Earth's surface.
1. Continental Drift: The Starting Point
In 1912, Alfred Wegener proposed that all continents were once part of a supercontinent called Pangaea.
Evidence for Continental Drift
Jigsaw Fit
Coastlines of Africa and South America match like puzzle pieces.
Fossil Evidence
Glossopteris, Mesosaurus found on separate continents.
Geological Evidence
Cape Fold Mountains (SA) align with Appalachian Mountains (USA).
Glacial Evidence
Striations in India, South Africa, and South America show that these areas were once much closer to the South Pole.
2. Mechanics of Plate Movement
Convection Currents
Heat from the core drives convection currents: magma rises, cools, sinks, and helps move the plates.
Sea Floor Spreading
Magma rises at mid-ocean ridges, creating new crust.
3. Types of Plate Boundaries
| Boundary Type | Movement | Resulting Landforms | Example |
|---|---|---|---|
| Divergent | Moving apart | Rift valleys, mid-ocean ridges | Mid-Atlantic Ridge |
| Convergent | Moving together | Fold mountains, trenches, volcanoes | Himalayas, Andes |
| Transform | Sliding past | Fault lines, earthquakes | San Andreas Fault |
Divergent
- Plates move apart
- New crust formed
- Mid-ocean ridges
Convergent
- Plates collide
- Mountains, trenches
- Subduction zones
Transform
- Plates slide past
- Earthquakes
- Fault lines
Practice & Assess
Six interactive games - all reset buttons work
Quiz 1 - Pangaea
Quiz 2 - True/False
"Transform boundaries create mountains"
Match - boundary types
Fill - supercontinent
Fill - driving force
Order - boundaries
Click to rearrange (conceptual order):
Key Terms
Key Recap
The main idea to remember is that moving plates shape major landforms and hazards. If you can explain continental drift, convection currents, and the three main plate boundaries, you will be in a strong position for exam questions in this section.
Exam Focus: Plate Boundaries
When answering plate tectonics questions, first identify the boundary type: constructive, destructive, or conservative. Then explain the movement of the plates and the result. Constructive boundaries pull apart and can form new crust, destructive boundaries move together and may cause subduction, while conservative boundaries slide past each other and often trigger earthquakes.
Use a labelled sketch whenever possible. Arrows showing plate movement, labels for magma or subduction, and the correct landform can turn a vague answer into a clear Geography explanation.
Also learn the link between boundary type and hazard. Volcanoes are common where magma reaches the surface, while earthquakes can occur at several boundary types because plates lock, build pressure, and then release energy suddenly.
For revision, compare two boundary types at a time and write one similarity and one difference. This helps you avoid listing facts without showing that you understand how the processes are connected to real landforms and hazards.
