Mafic magma

Definition

Mafic magma is a type of magma that is rich in magnesium and iron, characterized by its lower silica content compared to other types of magma. This composition leads to distinct properties, such as higher density and a tendency to produce dark-colored igneous rocks like basalt when it solidifies. Mafic magma plays a significant role in the formation of oceanic crust and volcanic activity, especially at mid-ocean ridges and hotspot volcanoes.

5 Must Know Facts For Your Next Test

1. Mafic magma typically has a temperature range between 1000°C to 1200°C, which allows for lower viscosity compared to felsic magma, enabling it to flow more easily.
2. The lower silica content in mafic magma results in less explosive volcanic eruptions, often producing gentle lava flows instead of violent pyroclastic activity.
3. Mafic magma is primarily produced at divergent tectonic plate boundaries, where tectonic plates move apart, allowing molten rock from the mantle to rise.
4. Common minerals found in mafic magma include olivine, pyroxene, and plagioclase feldspar, which contribute to the characteristic dark color of resulting igneous rocks.
5. As mafic magma cools, it can undergo fractional crystallization, altering its composition and potentially forming more evolved magmas with different properties.

Review Questions

• How does the composition of mafic magma influence its physical properties and behavior during volcanic eruptions?
  • The composition of mafic magma, with its high magnesium and iron content and low silica levels, results in a denser and less viscous material. This means that mafic magma tends to flow more freely than other types of magma. Consequently, eruptions involving mafic magma are typically less explosive, producing basaltic lava flows rather than violent eruptions characterized by pyroclastic flows. The physical properties of mafic magma significantly shape the landforms created during volcanic activity.
• Compare and contrast mafic magma with felsic magma in terms of composition, eruption style, and rock types formed.
  • Mafic magma is rich in magnesium and iron with lower silica content, leading to denser and darker-colored rocks like basalt when solidified. In contrast, felsic magma contains higher silica levels along with sodium and potassium, producing lighter-colored rocks such as granite. Eruptions from mafic magma are generally effusive with gentle lava flows, while those from felsic magma tend to be more explosive due to higher viscosity. These differences significantly affect the geological features formed at volcanic sites.
• Evaluate the role of mafic magma in the formation of oceanic crust and its implications for plate tectonics.
  • Mafic magma plays a crucial role in the formation of oceanic crust as it emerges at mid-ocean ridges where tectonic plates diverge. The upwelling of mafic material from the mantle contributes to the creation of new ocean floor as it cools and solidifies into basalt. This process not only shapes the oceanic crust but also drives plate tectonics by providing the material for sea-floor spreading. Understanding the behavior and characteristics of mafic magma enhances our knowledge of Earth's geodynamic processes and the ongoing evolution of its surface.

Related terms

Basalt:

A dark, fine-grained volcanic rock that forms from the rapid cooling of mafic magma, typically found in oceanic crust.

Felsic Magma: A type of magma that is rich in silica and contains higher concentrations of elements like potassium and sodium, leading to lighter-colored rocks such as granite.

Igneous Rock: Rock formed through the cooling and solidification of magma or lava, classified into two main types: intrusive (plutonic) and extrusive (volcanic).