Focuses of the chapter:
- Plate tectonics
- Plates and plate boundaries
- Internal processes
- Landforms and plate boundaries
- Tectonic hazards
- Factors affecting them
- Measures against
- Effectiveness of measures
- Staying or leaving in hazard-prone regions
Guiding Questions[edit | edit source]
- What has happened to areas with active tectonic activities?
- What areas have been frequently affected by earthquakes, volcanic eruptions and tsunamis?
- What spatial patterns exist in these natural hazards?
- Why are there such patterns? How is it related to the global distribution of plates and plate boundaries?
- What and where are major plates and plate boundaries?
- What are the related landform features found at plate boundaries? How re they formed?
- How does plate movement create natural hazards that develop with these features?
- Why are some earthquake and volcanic zones far away from plate boundaries?
Table of Contents[edit | edit source]
Plate Tectonics[edit | edit source]
The theory of plate tectonics was proposed by German meteorologist Alfred Wegener in 1912. The theory based on the idea of continental drifts describes the large-scale movements of the plates of the Earth's lithosphere.
The Earth can be structurally divided into three parts, namely crust, mantle and core. Use an egg as an analogue, the crust that is the outermost layer corresponds to the egg shell; the mantle in the middle corresponds to the egg white; and the core that is the innermost part corresponds to the egg yolk. However, this is an oversimplified picture, which can only be used to give you a rough idea.
The crust with thickness ranges from a few kilometres to tens of kilometres can be categorised into two groups, continental and oceanic crusts. As suggested by their names, the continental crusts contribute to the land of the Earth, whereas the oceanic crusts lie under the ocean. There are distinct differences between them, in terms of thickness, chemical composition, and so on.