Q 01/05

Plate tectonics describes the movement of pieces of which layer of the Earth?

A) The lithosphere

B) The inner mantle

C) The outer core

D) The asthenosphere

Answer · why

A) The lithosphere

This rigid outer shell, crust plus upper mantle, rides on the hotter, more ductile asthenosphere beneath.

Q 02/05

How many 'major' tectonic plates are usually counted?

A) Three or four

B) Eleven or twelve

C) Twenty or more

D) Seven or eight

Answer · why

D) Seven or eight

The Indo-Australian plate is sometimes split in two, which is why the count wobbles.

Q 03/05

What are the three types of plate boundary?

A) Oceanic, continental and mixed

B) Compressive, tensile and shear

C) Convergent, divergent and transform

D) Active, passive and dormant

Answer · why

C) Convergent, divergent and transform

Where two plates meet decides whether crust is destroyed, created or simply slides past.

Q 04/05

Plates typically move at speeds up to roughly how much per year?

A) About 10 metres

B) About 1 metre

C) About 10 cm

D) About 1 mm

Answer · why

C) About 10 cm

The Mid-Atlantic Ridge spreads at fingernail-growth pace; the Nazca plate races along at hair-growth pace, about 160 mm a year.

Q 05/05

What is the process called in which one plate is carried down beneath another into the mantle?

A) Obduction

B) Accretion

C) Subduction

D) Rifting

Answer · why

C) Subduction

It shrinks Earth's surface, which is balanced by new crust forming at spreading ridges, a tectonic 'conveyor belt'.