Flux melting

Definition

Flux melting refers to the process where the addition of volatile substances, such as water or carbon dioxide, lowers the melting temperature of rocks, leading to the generation of magma. This phenomenon is crucial in understanding how magma forms and evolves, as it influences the composition and properties of the resulting melt, ultimately affecting volcanic activity and the type of igneous rocks produced.

5 Must Know Facts For Your Next Test

1. Flux melting is particularly important at subduction zones where oceanic plates descend into the mantle, introducing water that lowers the melting point of surrounding mantle rocks.
2. The presence of volatiles not only lowers melting temperatures but also affects the chemical composition of the resulting magma, influencing its viscosity and potential for explosive eruptions.
3. Flux melting can lead to the formation of different types of magma, including basaltic and andesitic compositions, depending on the source rocks and the types of volatiles involved.
4. In addition to subduction zones, flux melting can also occur in other geological settings such as rift zones and hotspots where mantle plumes introduce heat and volatiles.
5. Understanding flux melting helps geologists predict volcanic activity and assess hazards associated with explosive eruptions that can be driven by volatile-rich magmas.

Review Questions

• How does flux melting contribute to the generation of magma at subduction zones?
  • Flux melting plays a significant role in magma generation at subduction zones by introducing water from descending oceanic plates into the mantle. This water acts as a flux, lowering the melting temperature of surrounding mantle rocks and causing them to partially melt. As a result, this process generates magma that can rise to form volcanic arcs, characterized by their explosive activity due to the high volatile content.
• Discuss how the presence of volatiles influences both magma composition and volcanic activity.
  • The presence of volatiles significantly influences magma composition by affecting its temperature and viscosity. When volatiles like water or carbon dioxide are present during flux melting, they lower the melting point of rocks and lead to a more silica-rich melt. This silica-rich magma tends to be more viscous and can trap gases, which increases pressure and contributes to more explosive volcanic eruptions compared to less viscous basaltic magmas.
• Evaluate the implications of flux melting for understanding volcanic hazards in different geological settings.
  • Evaluating flux melting is crucial for understanding volcanic hazards as it provides insight into how different geological settings can produce varied magma types. For example, in subduction zones, flux melting creates volatile-rich magmas that are prone to explosive eruptions, posing significant risks to nearby populations. Conversely, in hotspot environments where magma is generated through decompression rather than flux melting, eruptions tend to be less explosive. Understanding these differences helps geologists assess potential hazards and develop mitigation strategies.

Related terms

Magma: Magma is a molten rock material located beneath the Earth's surface that can form when rocks melt due to various factors including temperature and pressure changes.

Volatile: Volatiles are substances that can easily become gases at surface conditions, like water vapor or carbon dioxide, playing a significant role in melting processes.

Partial Melting: Partial melting occurs when only a portion of a solid material melts, leading to a melt with a different composition than the original solid.