Magma Composition

Deep within the Earth, rock melts under intense heat and pressure, forming magma.

Magma collects in magma chambers beneath the Earth's surface, often at plate boundaries or hotspots.

The flow of magma primarily depends on its viscosity. High-viscosity magma, rich in silica, traps gas, remaining below the surface or erupting explosively. This type is called felsic magma. Low-viscosity magma, which contains less silica, moves easily and reaches the surface as flowing lava. This is known as mafic magma.

When magma erupts, it can spread across the landscape in rivers of lava or explode into the air.

Thick lava can block vents, trapping gas until pressure builds up, triggering an explosive eruption that ejects pyroclasts.

Lava forms different types of flows. Pāhoehoe lava is thin and flows smoothly, forming twisted, ropy patterns. Its outer layer hardens while the inside remains molten, creating lava tubes.

Pillow lava forms when lava enters water, where the rapid cooling causes it to solidify. This process is common along mid-ocean ridges, where underwater volcanic activity is frequent.