Look at maps of volcanoes, earthquakes and island chains like the Philippines and Japon, and you can see the rough outlines of what are called tectonic plates – the several rigid pieces of the earth’s outer layer, thought to be in constant movement and collision against each other.

A. large pieces of the earth’s surface
B. significant movements of the earth
C. sudden eruptions of volcanoes
D. volcanoes, earthquakes and island chains