Strictly speaking there are two broad types of volcano, a stratovolcano and a shield volcano, although there are lots of different volcanic features that can form from erupted magma (such as cinder cones or lava domes) as well processes that shape volcanoes. In this article you can find out the difference between stratovolcanoes and shield volcanoes, as well as lava domes and calderas.
Why are there different types of volcano?
Viscosity is important in volcanology. An eruption of highly viscous (very sticky) magma tends to produce steep-sided volcanoes with slopes that are about 30–35°. That’s because the viscous volcanic material doesn’t flow that far from where it is erupted, so it builds up in layers forming a cone-shaped volcano known as a stratovolcano.
Shield volcanoes, on the other hand, have gentle slopes that are less than 10° and erupt more fluid lavas called basalt. When a shield volcano erupts, the basalt can flow great distances away from the vent to produce broad, gentle slopes…
Source: British Geological Survey (BGS) – Discovering Geology
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