Andesitic lava

Definition

Andesitic lava is a type of volcanic rock characterized by its intermediate silica content, typically between 53% and 63%. It is known for being more viscous than basaltic lava, resulting in a slower flow and the formation of distinct geological features such as lava domes and cryptodomes. The composition often includes minerals like plagioclase feldspar, pyroxene, and hornblende, which contribute to its unique properties.

5 Must Know Facts For Your Next Test

1. Andesitic lava typically erupts at temperatures between 800°C to 1,000°C (1,472°F to 1,832°F), which is cooler than basaltic lava.
2. Due to its higher viscosity, andesitic lava can lead to explosive eruptions, especially when gas builds up in the magma.
3. The presence of andesitic lava is often associated with subduction zones where oceanic plates collide with continental plates.
4. Andesitic lava contributes to the formation of stratovolcanoes, which are characterized by their steep profiles and alternating layers of lava and ash.
5. The slow flow of andesitic lava allows it to pile up in thick layers, resulting in the creation of distinctive landforms such as lava domes.

Review Questions

• How does the viscosity of andesitic lava affect volcanic eruptions compared to other types of lava?
  • Andesitic lava is more viscous than basaltic lava due to its intermediate silica content. This higher viscosity can trap volcanic gases more effectively, leading to increased pressure within the magma chamber. As a result, when andesitic lava erupts, it often produces more explosive eruptions compared to basaltic eruptions, which tend to flow more freely.
• Discuss the relationship between andesitic lava and the formation of stratovolcanoes.
  • Andesitic lava plays a crucial role in forming stratovolcanoes due to its intermediate viscosity and composition. When andesitic lava erupts, it tends to pile up near the vent rather than flow long distances, leading to the characteristic steep-sided profile of stratovolcanoes. Additionally, the explosive nature of andesitic eruptions contributes to layering ash and other volcanic materials with the lava flows, further shaping these impressive geological formations.
• Evaluate the impact of andesitic lava on both landforms and local ecosystems in areas surrounding stratovolcanoes.
  • Andesitic lava significantly influences landform development by creating features like lava domes and stratovolcanoes that alter local topography. The eruption of this type of lava can disrupt ecosystems by burying habitats under thick layers of material or changing water drainage patterns. However, these volcanic areas can also create fertile soils over time as weathering occurs, allowing for diverse plant life to thrive in nutrient-rich environments once the initial devastation has receded.

Related terms

Lava Dome: A steep-sided mound formed by the slow extrusion of viscous lava, often andesitic in composition, which piles up near the vent of a volcano.

Cryptodome: A type of dome that forms beneath the surface when magma accumulates, causing the overlying rock layers to bulge without erupting.

Volcanic Gas: Gases released from magma during a volcanic eruption, which can influence the type of lava produced and its eruptive behavior.