Andesitic Lava

Andesitic lava is a type of lava that is commonly associated with stratovolcanoes, which are characterized by their steep slopes and explosive eruptions. It is named after the Andes Mountains in South America, where this type of lava is often found.

Composition

Andesitic lava has a composition that is intermediate between the two other main types of lava, basaltic and rhyolitic. It is rich in silica, which makes it more viscous than basaltic lava but less viscous than rhyolitic lava. This intermediate viscosity contributes to the explosive nature of andesitic lava eruptions.

Physical Characteristics

When andesitic lava erupts, it tends to form thick, slow-moving flows that can travel short distances from the vent. These flows can also build up around the vent, leading to the formation of steep-sided stratovolcanoes.

Eruption Style

Andesitic lava eruptions are often explosive due to the high gas content and viscosity of the lava. The gas trapped within the viscous lava can lead to explosive eruptions, which can result in the ejection of ash, volcanic bombs, and pyroclastic flows.

Study Guide

1. What is andesitic lava named after?
2. Describe the composition of andesitic lava and how it compares to basaltic and rhyolitic lavas.
3. What are the physical characteristics of andesitic lava flows?
4. Explain why andesitic lava eruptions are often explosive.