Chapter 9: Problem 6

How do continental-rift eruptions form flood basalts? (D)

Short Answer

Expert verified

Continental-rift eruptions form flood basalts through a process involving the separation of tectonic plates, which causes the lithosphere to stretch and thin. This stretching allows magma from deep within the Earth's mantle to rise towards the surface, resulting in the extrusion of large volumes of low-viscosity, basaltic lava. Flood basalts form from multiple volcanic eruptions over a relatively short period of time, covering vast areas and creating multiple layers of lava, which accumulate over time to create a thick pile of basaltic rock.

Step by step solution

Understand Continental-Rift Eruptions

Continental-rift eruptions occur when tectonic plates separate, causing the lithosphere to stretch and thin. This stretching allows magma from deep within the Earth’s mantle to rise towards the surface. In these regions, the mantle partially melts due to decreased pressure in the form of basaltic magmas. Continental-rift eruptions are characterized by low-viscosity, basaltic lava that is volcanic in origin.

Recognize Flood Basalts

Flood basalts are vast areas of flat-lying, extensive lava flows that form from multiple volcanic eruptions over a relatively short period of time. These eruptions are characterized by the extrusion of large volumes of low-viscosity, basaltic lava that can cover wide areas, sometimes up to several thousand square kilometers. The resulting layers of basaltic rock are often many meters thick and can form plateaus or highlands.

Magma Rising Towards the Surface

When the lithosphere stretches and thins due to tectonic rifting, it creates pathways for the magma to reach the surface. The hot, low-viscosity basaltic magma can then flow easily through these pathways, filling up any available space. This leads to the eruption of vast amounts of molten rock, and ultimately, the formation of flood basalts.

Formation of Flood Basalts

As the basaltic magma reaches the surface during a continental-rift eruption, it rapidly spreads out over large areas. The low viscosity of the basaltic magma allows it to flow long distances from the source vent, covering vast areas and creating multiple layers of lava. Over time, these layers accumulate to create a thick pile of basaltic rock, forming the characteristic flood basalts.

Conclusion

Continental-rift eruptions form flood basalts through a process involving the separation of tectonic plates, stretching and thinning of the lithosphere, and the rising of low-viscosity basaltic magma towards the Earth's surface. When this magma erupts and spreads over large areas, it accumulates and forms the layers of basaltic rock that are characteristic of flood basalts.

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How do continental-rift eruptions form flood basalts? (D)

Short Answer

Step by step solution

Understand Continental-Rift Eruptions

Recognize Flood Basalts

Magma Rising Towards the Surface

Formation of Flood Basalts

Conclusion

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