Volatiles

Definition

Volatiles are substances in magma that can easily evaporate or vaporize at surface conditions, primarily consisting of water vapor, carbon dioxide, sulfur dioxide, and other gases. These components play a crucial role in influencing magma behavior, eruption dynamics, and the characteristics of volcanic eruptions. The presence and concentration of volatiles significantly affect magma viscosity, the potential for explosive eruptions, and the overall chemistry of volcanic products.

5 Must Know Facts For Your Next Test

1. Volatiles are crucial for determining whether an eruption will be explosive or effusive, as higher volatile content generally leads to more explosive behavior.
2. Water vapor is typically the most abundant volatile in magma, often making up a significant portion of the gas released during eruptions.
3. The amount of volatiles present in magma can influence its viscosity; more volatiles often lower viscosity, allowing for easier flow.
4. As magma rises, pressure decreases, allowing volatiles to expand and potentially lead to explosive decompression when the pressure drop is rapid.
5. Different types of volcanic rocks can be distinguished based on their volatile content and the resulting eruption styles, such as basaltic lavas being typically less volatile than rhyolitic lavas.

Review Questions

• How do volatiles influence the physical properties of magma and its eruptive behavior?
  • Volatiles have a significant impact on the physical properties of magma by affecting its viscosity and density. Higher concentrations of volatiles generally decrease viscosity, allowing magma to flow more easily. This change in flow dynamics can lead to different eruptive behaviors; for instance, low-viscosity magmas with fewer volatiles may produce gentle lava flows, while high-viscosity magmas rich in volatiles are more likely to result in explosive eruptions due to pressure build-up and rapid gas expansion.
• Discuss the role of degassing in relation to volcanic eruptions and how it is affected by volatile content.
  • Degassing plays a vital role in volcanic eruptions as it involves the release of gases from magma as it ascends toward the surface. The amount of volatiles present directly influences how much gas can be released. If volatiles are abundant and cannot escape quickly enough due to high viscosity or pressure conditions, they may cause a build-up that leads to explosive eruptions. Conversely, if gases escape gradually, eruptions may be less violent and more effusive.
• Evaluate how differences in volatile content among various magma types contribute to diverse eruption styles observed at different volcanoes.
  • Differences in volatile content among various types of magma—such as basaltic versus rhyolitic—greatly affect eruption styles. Basaltic magma typically has lower volatile content and higher temperatures, leading to relatively gentle eruptions characterized by lava flows. In contrast, rhyolitic magma has a higher volatile content and greater viscosity, resulting in more explosive eruptions. This variance illustrates how volatile composition not only determines eruption style but also influences geological processes such as the formation of different volcanic landforms and hazards associated with specific volcanoes.

Related terms

Magma Viscosity: The measure of a fluid's resistance to flow, which is influenced by the composition of the magma, particularly its volatile content.

Degassing:

The process through which gases are released from magma as it ascends towards the surface, significantly affecting eruptive behavior.

Eruption Style: Refers to the manner in which volcanic eruptions occur, which can range from effusive lava flows to explosive events based on the volatile content in the magma.