Pahoehoe lava flow

Magma is called lava after it erupts from a volcano. Different types of eruption result in different types of lava.

For example, shield volcanoes such as Kilauea on the island of Hawaii produce large amounts of lava that is less viscous (less sticky) because it has less silica, SiO2, in it. Lava from these eruptions may flow as a rough textured type called aa (a Hawaiian word, pronounced "ah, ah"), or another type called pahoehoe, which often has wrinkle folds on its surface. During an eruption, pahoehoe may change into aa as it becomes more viscous.

Composite volcanoes such as Mount St Helens generally have relatively small amounts of viscous lava. The sticky nature of the lava and the magma that forms it is caused by its relatively high silica content and makes these eruptions very explosive.

Image: A pahoehoe basalt lava flow from Kilauea volcano on the island of Hawaii (credit: Stephen & Donna O'Meara/SPL)


Pahoehoe lava flow Lava

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