Basalt

Definition

Basalt is a dark, fine-grained volcanic rock that is primarily composed of plagioclase and pyroxene minerals. It plays a crucial role in the formation of oceanic crust, as it is the most abundant rock type found beneath the oceans. Basalt forms from the rapid cooling and solidification of lava that erupts at mid-ocean ridges, making it essential for understanding the processes involved in oceanic crust formation and evolution.

5 Must Know Facts For Your Next Test

1. Basalt forms from low-viscosity lava that flows easily, allowing it to cover large areas and create extensive oceanic crust.
2. As new basalt is added to the ocean floor at mid-ocean ridges, older basalt is pushed away, leading to the recycling of oceanic crust over geological time scales.
3. The composition of basalt can vary based on factors like magma source and crystallization conditions, leading to different types of basalt with varying mineral content.
4. Basalt's density is higher than that of continental crust rocks like granite, contributing to the differences in elevation between ocean basins and continents.
5. When basalt undergoes weathering and alteration, it can produce minerals like clay and iron oxides, which play roles in marine ecosystems.

Review Questions

• How does basalt contribute to the formation of oceanic crust at mid-ocean ridges?
  • Basalt is formed from lava that erupts at mid-ocean ridges, where tectonic plates diverge. As magma rises from the mantle and erupts onto the seafloor, it cools rapidly upon contact with seawater, solidifying into basalt. This process creates new oceanic crust that continuously extends the ocean floor as seafloor spreading occurs.
• In what ways does the composition of basalt influence its role in the evolution of oceanic crust?
  • The composition of basalt directly affects its physical properties and behavior during geological processes. For instance, variations in mineral content can determine how basalt interacts with seawater, influences hydrothermal systems, and contributes to sediment formation on the ocean floor. This variability also impacts how basalt-rich regions respond to tectonic movements and their role in creating geological features like ridges and trenches.
• Evaluate the significance of basalt in understanding plate tectonics and its broader implications for oceanic processes.
  • Basalt serves as a critical indicator for studying plate tectonics due to its ubiquitous presence in oceanic crust formation. By examining basalt's characteristics, such as its mineral composition and distribution patterns, scientists can gain insights into mantle dynamics, volcanic activity, and the movement of tectonic plates. Understanding these processes is crucial for addressing larger questions about Earth's geological history, climate change, and marine ecosystems influenced by oceanic crust dynamics.

Related terms

Mid-Ocean Ridge: A continuous mountain range under the ocean formed by plate tectonics, where new oceanic crust is created through volcanic activity.

Igneous Rock: A type of rock formed through the cooling and solidification of magma or lava, which includes both basalt and granite.

Seafloor Spreading:

The process by which new oceanic crust is formed at mid-ocean ridges and gradually moves away from the ridge, allowing for the expansion of ocean basins.