Mafic magma

Definition

Mafic magma is a type of magma that is rich in magnesium and iron, resulting in a lower viscosity and higher temperature compared to other magma types. This composition leads to specific volcanic behaviors and landforms, particularly in areas where tectonic plates diverge or at hotspots. Mafic magma is typically associated with shield volcanoes and basaltic lava flows, which are key features of volcanic activity in certain geological settings.

5 Must Know Facts For Your Next Test

1. Mafic magma typically has a temperature range of about 1,100 to 1,200 degrees Celsius, which allows it to flow more easily than more viscous magma types.
2. The presence of iron and magnesium gives mafic magma its darker color and contributes to the formation of basalt when it solidifies.
3. Mafic eruptions tend to be less explosive than those involving more viscous magma types like rhyolitic magma, resulting in relatively gentle lava flows.
4. In divergent plate boundaries, mafic magma can create new oceanic crust as it rises between tectonic plates and solidifies upon cooling.
5. The formation of large shield volcanoes like Mauna Loa in Hawaii is primarily due to repeated eruptions of mafic magma.

Review Questions

• How does the composition of mafic magma affect volcanic landforms and eruption styles?
  • Mafic magma's high temperature and low viscosity lead to the formation of broad shield volcanoes with gentle slopes due to its ability to flow easily over long distances. This contrasts with more viscous magmas that can result in steep-sided stratovolcanoes. The fluid nature of mafic lava also results in less explosive eruptions, allowing for the creation of extensive basaltic lava fields.
• Discuss the relationship between mafic magma and divergent tectonic plate boundaries.
  • At divergent tectonic plate boundaries, mafic magma rises from the mantle as tectonic plates pull apart. This process results in the formation of new oceanic crust as the mafic lava erupts onto the seafloor or creates volcanic islands. The low viscosity of mafic magma allows for frequent but less explosive eruptions, contributing significantly to the geological landscape at these boundaries.
• Evaluate the impact of mafic magma on global volcanic activity and geological features.
  • Mafic magma plays a crucial role in global volcanic activity by creating features like mid-ocean ridges and large shield volcanoes. Its frequent eruptions contribute to the construction of new oceanic crust, affecting ocean circulation patterns and marine ecosystems. Furthermore, the vast basaltic plateaus formed by mafic lava flows can influence terrestrial environments and climate over geological time scales, illustrating its significant impact on Earth's geology.

Related terms

Basalt: A common volcanic rock that is primarily formed from mafic magma, characterized by its dark color and fine-grained texture.

Shield Volcano: A broad, domed volcano built up by the flow of low-viscosity mafic lava, resulting in gentle slopes.

Volcanic Divergence: The process occurring at divergent tectonic plate boundaries where magma rises to create new crust, often leading to volcanic activity.