Properties of Magma

Not all magma is the same. The composition and viscosity of magma can vary. These properties affect how fast the lava flows and the type of volcano that forms.

Although magma is a complex mixture, it is primarily composed of silica. Magma can contain from 50 to 70 % silica.

Viscosity is a liquid's resistance to flow. High viscosity magma is sticky and flows very slowly. Low viscosity magma flows more quickly.

Magma with high silica content has a higher viscosity and produces light-colored lava that later forms rhyolite. Magma with less silica and a lower viscosity produces dark lava that forms basalt.

Higher temperatures make magma and lava more fluid, lowering the viscosity. Pahoehoe is a type of very hot, fast-moving lava with low viscosity. Slower-moving, cooler, high-viscosity lava is known as aa.