Partial Melting

Definition

Partial melting is the process where only a portion of a solid material melts, resulting in a liquid phase that is often different in composition from the original solid. This phenomenon is crucial in understanding how different layers of the Earth, like the crust and mantle, evolve and differentiate over time, especially during magma generation and magmatic differentiation.

5 Must Know Facts For Your Next Test

1. Partial melting typically occurs at specific temperatures and pressures, which can vary depending on the composition of the rock being melted.
2. Different minerals have different melting points; thus, partial melting can lead to a magma that is enriched in certain elements or minerals while leaving others behind.
3. The process of partial melting is fundamental in the formation of igneous rocks, as it generates magma that rises to form volcanoes and other geological features.
4. As partial melting occurs within the mantle, it can lead to the generation of basaltic magma, which is common at mid-ocean ridges and hotspots.
5. Understanding partial melting helps explain the chemical diversity observed in igneous rocks, as different sources and degrees of melting can yield a wide range of rock types.

Review Questions

• How does partial melting contribute to planetary differentiation?
  • Partial melting plays a significant role in planetary differentiation by allowing materials within a planet to separate based on their melting points. As a planet heats up, certain components may melt while others remain solid. This process enables denser materials to sink towards the center while lighter materials rise, contributing to the layered structure observed in planetary bodies like Earth.
• Discuss how partial melting affects the composition of magma generated from mantle rocks.
  • Partial melting alters the composition of magma generated from mantle rocks by allowing certain minerals with lower melting points to melt first. This leads to magma that is often richer in silica and other elements compared to its source material. The degree of partial melting influences the overall chemical makeup of the resulting magma, which ultimately affects volcanic activity and the types of igneous rocks produced.
• Evaluate the role of partial melting in magmatic differentiation and its impact on crust formation.
  • Partial melting significantly influences magmatic differentiation by determining which minerals crystallize from a cooling magma. As partial melting occurs, variations in temperature and pressure lead to diverse magma compositions. This process not only affects what types of rocks are formed but also contributes to the development of continental crust by creating different layers with distinct mineralogies, affecting tectonic processes and shaping the Earth’s surface over geological time.

Related terms

Fractional Crystallization: The process whereby different minerals crystallize from a cooling magma at different temperatures, leading to a change in the composition of the remaining liquid.

Magma: A molten rock found beneath the Earth's surface that can solidify to form igneous rocks once it cools.

Geotherm: The gradient of temperature with depth in the Earth, which influences the conditions under which partial melting occurs.