The Earth's internal structure and the global pattern of plates

Overview

Recall questions on the layers of the Earth, the lithosphere and asthenosphere, oceanic and continental crust, the solid inner core, the Moho, radioactive heat and mantle convection, ridge push and slab pull, plate speeds, the seven major plates, the distribution of earthquakes and volcanoes, the Pacific Ring of Fire, mantle plumes, and GPS measurement.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   Name the four main layers of the Earth in order from the surface to the centre.

   Model answer

   The crust, the mantle, the outer core and the inner core.

2. 2

   What is the lithosphere?

   Model answer

   The rigid outer shell of the Earth, made up of the crust and the solid uppermost mantle, broken into tectonic plates and roughly 100 km thick.

3. 3

   What is the asthenosphere, and why does it matter for plate movement?

   Model answer

   It is the weak, partly molten layer of upper mantle beneath the lithosphere, roughly 100 to 300 km deep, and its ductile behaviour allows the rigid plates above to slide over it.

4. 4

   Give two ways in which oceanic crust differs from continental crust.

   Model answer

   Oceanic crust is thinner, at about 5 to 10 km against 30 to 70 km, and denser, at around 3.0 g cm⁻³ against 2.7 g cm⁻³.

5. 5

   Which rock type dominates oceanic crust, and which dominates continental crust?

   Model answer

   Oceanic crust is dominated by basalt, and continental crust by granite.

6. 6

   Why is the inner core solid when it is hotter than the liquid outer core?

   Model answer

   The pressure at the centre of the Earth is so great that it raises the melting point of iron above the temperature there, so the inner core stays solid.

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