Pahoehoe Lava

Synonyms

Ropy lava; Shelly lava; Slabby lava

Definition

Pahoehoe (the word is Hawaiian for ropy) lava is the term for cooling textures of a highly fluid, gas-charged lava flows and was introduced as a technical term by Clarance Dutton, 1883. The surface of Pahoehoe lava is usually smooth, undulant, or ropy (Figure 1). These textures are created by deformation of the flow. As the lava cools, the molten rock becomes more viscous (resistant to flow) and behaves more like a plastic. The moving flow cools from the outside toward the inside and a skin is created at the atmosphere-lava interface, whereas the center is still moving and flowing and tries to escape the surrounding skin. Due to this behavioral difference between the center and the skin, the skin can bunch upward or create wrinkles which can sometimes look like ropes and therefore is called ropy pahoehoe. In cases where the surface is creating more shelly textures the pahoehoe is called Shelly pahoehoeand where the surface is...