Pahoehoe refers to a type of lava flow that has a smooth and often ropy or wrinkled surface texture. It is one of the primary types of lava flows and is commonly associated with basaltic lava eruptions. Pahoehoe lava flows result from the low viscosity of basaltic lava, which allows it to flow more fluidly compared to other types of lava.
Key points about pahoehoe include:
- Surface Texture: Pahoehoe lava flows have a smooth, undulating, and ropy texture on their surface. The term “pahoehoe” is derived from the Hawaiian language and means “smooth, unbroken lava.”
- Basaltic Composition: Pahoehoe flows are often associated with basaltic lava, which has a relatively low viscosity due to its composition of low silica content. This low viscosity allows the lava to flow more easily and form distinctive textures.
- Formation: Pahoehoe flows form when basaltic lava flows quickly and smoothly over the ground, creating a continuous, fluid surface. As the lava cools and solidifies, its outer layer forms the characteristic ropy texture.
- Ropey Structures: The ropy or wrinkled appearance of pahoehoe flows is caused by the folding and stretching of the still-molten interior of the lava flow as the outer surface cools and solidifies. This creates elongated, rope-like structures known as “pahoehoe toes.”
- Advancing Front: Pahoehoe flows tend to have a relatively slow-moving advancing front due to their low viscosity. This allows them to travel greater distances before solidifying.
- Variations: Within pahoehoe flows, there can be variations in the appearance of the surface texture. These variations can result from changes in lava temperature, flow rate, and interaction with underlying terrain.
- Contrast with ‘A’a: Another type of lava flow, called ” ‘a’a,” has a rough, fragmented, and clinkery surface. ‘A’a flows result from more viscous lava and can be more difficult to traverse compared to the smoother pahoehoe flows.
Pahoehoe lava flows are common features in volcanic regions, particularly in areas with basaltic volcanism. They create distinct surface textures that can be observed in volcanic landscapes, providing valuable insights into past volcanic activity. Understanding the characteristics and behaviors of different types of lava flows is important for studying volcanic processes and hazards.