Vulcanicity

Syllabus tag: KCSE | Geography | Form 2 | Topic 11 Vulcanicity

Lesson objectives

By the end of this topic, you should be able to:

• Define vulcanicity and explain its causes.
• Describe the intrusive features formed by vulcanicity.
• Describe the extrusive features, including types of volcanoes and craters.
• Explain the world distribution of volcanoes and the significance of vulcanicity.

Summary

Vulcanicity is the movement of molten rock into or onto the earth's crust. Where magma cools within the crust it forms intrusive features — sill, dyke, laccolith, batholith. Where it reaches the surface it forms extrusive features — volcanoes, lava plateaus, craters. Lava type decides the shape: acidic gives steep domes, basic gives gentle shields.