Dehydration melting

Definition

Dehydration melting refers to the process whereby water is released from minerals under high temperature and pressure, leading to the formation of magma. This occurs mainly in subduction zones, where an oceanic plate descends into the mantle, causing the surrounding rock to melt as a result of the removal of water from hydrous minerals. The resulting magma contributes to volcanic activity at convergent plate boundaries.

5 Must Know Facts For Your Next Test

1. Dehydration melting predominantly occurs at convergent plate boundaries, particularly in subduction zones where oceanic plates sink beneath continental plates.
2. The released water from hydrous minerals lowers the melting point of the surrounding mantle rock, facilitating magma formation.
3. As the magma rises towards the surface, it can lead to explosive volcanic eruptions due to the high gas content that accumulates during the melting process.
4. Dehydration melting is a crucial mechanism for producing intermediate to felsic magmas, which are characteristic of volcanic arcs associated with subduction.
5. The process also plays a role in recycling water back into the mantle, contributing to long-term geological cycles and influencing mantle composition.

Review Questions

• How does dehydration melting contribute to magma formation at subduction zones?
  • Dehydration melting contributes to magma formation at subduction zones by facilitating the release of water from hydrous minerals in descending oceanic plates. As these minerals release water under high temperatures and pressures, it lowers the melting point of surrounding mantle rocks. This process allows for more efficient generation of magma, which can rise towards the surface and potentially lead to volcanic eruptions.
• Discuss the implications of dehydration melting on volcanic activity at convergent plate boundaries.
  • Dehydration melting has significant implications for volcanic activity at convergent plate boundaries. The water released from hydrous minerals not only aids in lowering the melting point of surrounding rocks but also contributes to the gas content in rising magma. This can result in explosive eruptions when gases become trapped as magma ascends, causing increased pressure within magma chambers and leading to violent volcanic events characteristic of subduction-related volcanoes.
• Evaluate the role of dehydration melting in the broader context of plate tectonics and its effects on Earth's geology.
  • Dehydration melting plays a critical role in understanding plate tectonics and its effects on Earth's geology by illustrating how interactions between tectonic plates lead to volcanic activity and landform development. As oceanic plates subduct beneath continental plates, the process generates magma through dehydration melting, influencing volcanic arcs and mountain building. Furthermore, this mechanism contributes to the recycling of water back into the mantle and plays a role in global geochemical cycles, shaping not only volcanic landscapes but also influencing climate over geological timescales.

Related terms

Subduction Zone:

A region of the Earth's crust where one tectonic plate moves under another, leading to volcanic activity and the formation of mountain ranges.

Magma Generation: The process by which molten rock is formed from solid rock due to changes in temperature, pressure, and composition.

Hydrous Minerals: Minerals that contain water in their crystal structure, which can release water when subjected to high temperatures and pressures.