Andesitic Lava
Andesitic lava is a type of lava that is commonly associated with explosive volcanic eruptions. It is named after the Andes Mountains in South America, where it is often found.
Composition
Andesitic lava is composed of approximately 52-63% silica, which gives it a high viscosity. This high viscosity means that andesitic lava does not flow easily and tends to form thick, blocky flows.
Characteristics
- Viscosity: Andesitic lava has a high viscosity, which means it does not flow easily. This can lead to the formation of steep-sided volcanoes.
- Color: It is typically gray to black in color.
- Gas Content: Andesitic lava often contains a high amount of dissolved gases, which can lead to explosive eruptions.
- Formation: Andesitic lava is formed at subduction zones, where oceanic crust is being pushed beneath continental crust.
- Mineral Composition: It contains minerals such as plagioclase, amphibole, and pyroxene.
Volcanic Hazards
Due to its high gas content and viscosity, andesitic lava eruptions can be highly explosive and pose significant hazards to surrounding areas. These hazards can include pyroclastic flows, ash fall, and lahars.
Study Guide
When studying andesitic lava, it's important to focus on the following key points:
- Understand the composition of andesitic lava, including its silica content and mineral composition.
- Learn about the characteristics of andesitic lava, such as its viscosity, color, and gas content.
- Explore the formation of andesitic lava at subduction zones and its association with volcanic arcs.
- Understand the hazards associated with andesitic lava eruptions, including explosive eruptions and the formation of volcanic hazards.
- Compare and contrast andesitic lava with other types of lava, such as basaltic and rhyolitic lava.
By understanding these key points, you can gain a comprehensive understanding of andesitic lava and its significance in the context of volcanic activity.
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