Question

Which of the following layers is believed to be the source of magma that causes volcanic eruptions?

• A. Lithosphere
• B. Mantle
• C. Asthenosphere
• D. Barysphere

Answer 1

Answer:

C. Asthenosphere

• Correct Answer: Option C (Asthenosphere)

• The asthenosphere is the primary source of magma that causes volcanic eruptions. Located in the upper mantle beneath the lithosphere, the asthenosphere is a semi-molten layer of rock that exists at depths of approximately 80-200 kilometers below the Earth's surface.

• The asthenosphere has several key characteristics that make it the source of magma:

• 1. Temperature and Pressure: The asthenosphere experiences high temperatures (around 1300-1600°C) and moderate pressure conditions that keep the rock in a partially molten state.

• 2. Partial Melting: Due to the specific temperature-pressure conditions, rocks in the asthenosphere undergo partial melting, creating pockets of molten rock (magma).

• 3. Convection Currents: The asthenosphere experiences convection currents that help transport the molten material upward toward the Earth's surface.

• 4. Tectonic Activity: At plate boundaries, the asthenosphere's magma can rise through cracks and weaknesses in the overlying lithosphere, eventually reaching the surface as volcanic eruptions.

• While the lithosphere is the outermost solid layer, the mantle (including the asthenosphere) is the deeper layer, and the barysphere refers to the Earth's core - it is specifically the asthenosphere within the upper mantle that provides the ideal conditions for magma generation and volcanic activity.