Types of Volcanoes: Shield vs Composite
Shield volcanoes are the gentle giants of the volcanic world. They've got slopes less than 10 degrees - imagine a warrior's shield lying flat on the ground. These volcanoes are made entirely of basaltic lava that's really hot and flows easily because it's low in silica.
The key thing about shield volcanoes is that they're not dramatic at all. The low viscosity magma flows smoothly down the gentle slopes, building up the volcano bit by bit. You won't find much explosive material here - eruptions are quiet, frequent, and produce loads of fluid lava through fissure eruptions on the sides.
Composite volcanoes (also called strato-volcanoes) are completely different beasts. They're tall, steep-sided cones made of alternating layers of lava and ash - like a geological layer cake. The magma here is andesitic with medium viscosity, so it doesn't flow far from the base.
Quick Tip: Remember that composite volcanoes are found at convergent margins where oceanic crust gets pushed under continental crust - think Mt. St. Helens!
These volcanoes are proper explosive. Higher gas content means pyroclastic flows and much more dangerous eruptions that can last ages.
