Pahoehoe

Definition

Pahoehoe is a type of basaltic lava flow characterized by its smooth, ropy, and undulating surface texture. This unique form of lava flow is significant in understanding volcanic products, the mechanisms behind effusive eruptions, the hazards associated with lava flows, and the various types of lava behavior. Pahoehoe typically results from low-viscosity lava that allows for the formation of these distinctive shapes as it cools and solidifies.

5 Must Know Facts For Your Next Test

1. Pahoehoe forms from low-viscosity basaltic lava that can flow easily over long distances, leading to widespread lava fields.
2. The formation of pahoehoe often occurs in active volcanic regions, where lava flows can create various landforms such as pahoehoe benches and toes.
3. As pahoehoe cools, its surface can develop unique textures including ropes or billows due to the movement of underlying molten material.
4. Pahoehoe flows can transition into aa flows if the viscosity increases or if the flow rate decreases, resulting in a different texture.
5. Pahoehoe lava is less hazardous than aa lava because it tends to move more predictably and can be more easily observed during eruptions.

Review Questions

• How does the viscosity of pahoehoe lava influence its flow characteristics compared to other types of lava?
  • Pahoehoe lava has a low viscosity, which allows it to flow smoothly and cover larger distances without breaking apart. This contrasts with higher viscosity lavas like aa, which have a more rugged and jagged surface due to their inability to flow as easily. The smooth texture of pahoehoe is a direct result of its fluid nature during eruption, leading to more predictable movement and distinct formations.
• What role do pahoehoe flows play in assessing volcanic hazards and planning mitigation strategies?
  • Understanding pahoehoe flows is essential for assessing volcanic hazards because they typically move predictably and can travel significant distances. This knowledge aids in creating effective evacuation plans and safety measures for nearby communities. By recognizing the characteristics of pahoehoe, scientists can forecast potential flow paths and help mitigate risks associated with volcanic eruptions.
• Evaluate how pahoehoe contributes to the formation of unique geological features and what this reveals about volcanic activity over time.
  • Pahoehoe significantly contributes to the formation of geological features like pahoehoe benches and tubes, revealing patterns of past volcanic activity. These features indicate not only the characteristics of the lava but also the dynamic processes at play during eruptions. Analyzing these formations helps geologists understand eruption history, magma composition, and the evolution of volcanic landscapes over time, providing insights into both current activity and future risks.

Related terms

Aa: Aa is another type of basaltic lava flow that has a rough, jagged, and clinkery surface, contrasting with the smooth texture of pahoehoe.

Viscosity: Viscosity is a measure of a fluid's resistance to flow; in volcanic terms, lower viscosity allows for smoother flows like pahoehoe, while higher viscosity results in thicker, slower-moving lava.

Lava Tube: Lava tubes are natural conduits formed by flowing lava that moves beneath the surface, often resulting from pahoehoe flows cooling on the surface while allowing molten material to flow underneath.