Basalt

Definition

Basalt is a dark, fine-grained volcanic rock that forms from the rapid cooling of low-viscosity lava rich in iron and magnesium. It is one of the most abundant types of igneous rock found on Earth and plays a crucial role in understanding the formation and classification of various Earth materials, particularly in relation to oceanic crust and volcanic activity.

5 Must Know Facts For Your Next Test

1. Basalt is primarily composed of plagioclase feldspar and pyroxene minerals, which contribute to its dark color and density.
2. Most of the oceanic crust is made up of basalt, which forms when magma rises from the mantle at mid-ocean ridges and cools rapidly in contact with seawater.
3. Basalt can form large volcanic landforms such as shield volcanoes, which have broad, gently sloping sides due to the fluid nature of basaltic lava.
4. The texture of basalt can vary from fine-grained to porphyritic, depending on the rate of cooling and the presence of larger mineral crystals.
5. Basalt is often used in construction, for roads and buildings, due to its durability and abundance.

Review Questions

• How does basalt's formation process differ from that of other igneous rocks?
  • Basalt forms specifically from the rapid cooling of low-viscosity lava that is rich in iron and magnesium, making it distinct from other igneous rocks that may form from slower cooling magma. This rapid cooling typically occurs when lava erupts onto the Earth's surface during volcanic activity. In contrast, other igneous rocks like granite form from the slow crystallization of magma deep within the Earth, resulting in larger crystals and a different texture.
• Discuss the significance of basalt in understanding oceanic crust composition and plate tectonics.
  • Basalt is significant for understanding oceanic crust because it constitutes the majority of this layer beneath oceans. As new basalt forms at mid-ocean ridges through volcanic activity, it plays a key role in the process of seafloor spreading, which is essential for plate tectonics. The formation and recycling of basalt during tectonic processes help explain how continents drift apart over geological time and contribute to our knowledge about Earth's dynamic systems.
• Evaluate how basalt's properties influence its practical applications in construction and engineering.
  • Basalt's properties, such as its durability, strength, and resistance to weathering, make it an excellent material for various construction applications. Its fine-grained structure allows for easy cutting and shaping while maintaining structural integrity. Engineers often utilize crushed basalt in road construction, building foundations, and as aggregates in concrete. Furthermore, basalt fiber is increasingly used in advanced materials due to its high tensile strength and resistance to thermal deformation, showcasing its versatility beyond traditional uses.

Related terms

Igneous Rock: Rock formed through the cooling and solidification of molten material, either magma beneath the Earth's surface or lava exposed at the surface.

Lava Flow: A stream of molten rock that emerges from a volcano or fissure and solidifies as it cools, typically forming basalt when low-viscosity lava is involved.

Pumice: A light, porous volcanic rock that forms when volcanic lava cools quickly and traps gas bubbles, often found in association with basaltic eruptions.