Pangaea
Pangaea was a supercontinent where all Earth’s continents were joined together about 300 million years ago.
Breakup of Pangaea
Pangaea later split into two large landmasses:
Laurasia
Northern supercontinent:
- North America
- Europe
- Asia
Gondwana
Southern supercontinent:
- Australia
- Antarctica
- Africa
- South America
- India
Alfred Wegener
In 1912, Wegener proposed the theory of continental drift:
- continents move slowly over time
- continents were once connected
Scientists first rejected his idea because he could not explain how continents moved.
Evidence for Continental Drift
1. Matching Coastlines
Continents such as Africa and South America fit together like puzzle pieces.
2. Fossil Evidence
Same fossils found on continents now separated by oceans.
Examples:
- Mesosaurus
- Glossopteris
3. Rock and Mountain Evidence
Similar rock types and mountain ranges found on different continents.
4. Climate Evidence
Glacial evidence found in places that are now warm.
Plate Tectonics Theory
Modern theory explaining continental movement.
Earth’s crust is broken into tectonic plates that move slowly over the mantle.
Layers of Earth
| Layer | Description |
|---|---|
| Crust | Thin outer layer |
| Mantle | Hot semi-solid rock |
| Core | Very hot centre |
Mantle Convection
Heat inside Earth causes movement in the mantle.
This movement pushes tectonic plates.
Types of Plate Boundaries
| Boundary Type | Movement | Results |
|---|---|---|
| Divergent | Plates move apart | Volcanoes, new crust |
| Convergent | Plates move together | Mountains, earthquakes, volcanoes |
| Transform | Plates slide past | Earthquakes |
Seafloor Spreading
New crust forms at mid-ocean ridges and moves outward.
This provided evidence supporting plate tectonics.
Key Terms
| Term | Meaning |
|---|---|
| Continental Drift | Continents moving over time |
| Plate Tectonics | Modern theory explaining plate movement |
| Pangaea | Ancient supercontinent |
| Gondwana | Southern supercontinent |
| Laurasia | Northern supercontinent |
| Mantle Convection | Movement of hot mantle rock |
| Subduction | One plate forced beneath another |
Important Exam Points
✅ Continental drift = Wegener’s original theory
✅ Plate tectonics = accepted modern explanation
✅ Australia was part of Gondwana
✅ Evidence is important in science
Quick Summary
\text{Pangaea split into Laurasia and Gondwana before tectonic plates moved continents into their current positions.}
- Continents were once connected
- Evidence includes fossils, rocks, coastlines, and climate
- Tectonic plates move due to mantle convection
- Plate movement causes earthquakes, volcanoes, and mountains