Activities
Sum Up
l The structure of the earth includes its inner core, outer core, mantle and crust. The crust is divided into plates.
l The theory of plate tectonics teaches that plates float on the mantle and move slowly on the crust. The theory is based on the theories of continental drift and sea-floor spreading.
l Convection currents of magma in the earth’s mantle cause the earth’s crust to break up into moving plates that diverge and converge.
l Plate boundaries are places where plates meet. Some types of plate boundaries and their characteristics include:
Type of boundary Processes involved Results of processes Examples Destructive
plates converge subduction
volcanic activity faulting folding
Constructive plates separate ocean trenches
volcanic mountains Japan fold mountains earthquakes
new oceanic crust
sea-floor spreading mid-ocean ridges volcanic activity faulting
Conservative
plates slide past each other
transform faults earthquakes
volcanic mountains earthquakes
San Andreas Fault
l Ireland’s location in the world and its position in relation to plates has changed over time.
Mid-Atlantic Ridge Iceland
Andes area
1. Use the diagram provided to help you to explain the key features of the theory of plate tectonics. (LC Ordinary Level – 40 marks)
2. Explain – with the aid of a labelled diagram or diagrams – the process of global crustal plate movement as it is currently understood. (LC Higher Level sample paper 2006 – 30 marks)
3. ‘Plate boundaries are zones where crust is both created and destroyed.’ Examine the above statement, with reference to examples you have studied. (LC Higher Level – 30 marks)
12 See Chapter 1 of your Workbook
Plates pulling apart
Convection currents rise up
Plates coming together
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