Block lava

Definition

Block lava is a type of lava flow characterized by its thick, viscous nature, which results in a rough, jagged surface as it cools and solidifies. This type of lava typically comes from volcanic eruptions that are more explosive in nature, leading to the formation of large, angular blocks rather than smooth, fluid flows. The presence of block lava indicates a high viscosity and temperature, which can significantly affect the landscape and environment around a volcano.

5 Must Know Facts For Your Next Test

1. Block lava flows are typically found in stratovolcanoes and shield volcanoes, where explosive eruptions occur.
2. The surface of block lava can be extremely rugged, often creating steep slopes and hazardous terrain.
3. As block lava cools, it may crack and break into large chunks or blocks, giving it its name.
4. Block lava has a higher temperature compared to other types of lava flows due to its higher gas content before erupting.
5. Unlike more fluid types of lava, block lava does not travel far from the eruption site because of its thickness and low mobility.

Review Questions

• How does the viscosity of block lava affect its movement and the formation of volcanic landscapes?
  • The high viscosity of block lava restricts its flow and movement, making it less mobile than other types of lava. This results in the creation of steep, rugged terrains near the volcano. As the block lava cools, it solidifies into large angular blocks rather than flowing smoothly over the ground. The thick nature of block lava also means that it accumulates near the vent rather than spreading over large distances.
• Compare and contrast block lava with pahoehoe in terms of physical characteristics and eruption styles.
  • Block lava is characterized by its rough, jagged surface and is associated with more explosive eruption styles, leading to thicker and less mobile flows. In contrast, pahoehoe is smooth and ropy, formed from more fluid lava that allows it to spread over larger areas easily. While block lava typically forms in stratovolcanoes with more violent eruptions, pahoehoe is often found in shield volcanoes where lava flows are less viscous and more gentle.
• Evaluate the impact of block lava on volcanic hazards and community safety during eruptions.
  • Block lava presents significant hazards during volcanic eruptions due to its ability to create steep slopes and unstable terrain. Communities located near volcanoes that produce block lava must be prepared for potential destruction caused by falling blocks or flows advancing down slopes. The thick nature of block lava also contributes to longer-lasting volcanic events as it does not flow away quickly, necessitating longer evacuation plans for nearby populations. Understanding the behavior of block lava helps in developing effective safety measures and emergency responses for affected communities.

Related terms

Viscosity: A measure of a fluid's resistance to flow, which in the case of lava, determines how easily it can move and spread.

Pahoehoe: A type of lava flow that is smooth and ropy in appearance, contrasting with the rough surface of block lava.

Volcanic eruption: The process by which magma from beneath the Earth's crust escapes to the surface, leading to the release of lava, ash, and gases.