The primary cause of volcanic eruptions is the movement of tectonic plates, which can lead to the melting of rocks in the Earth’s mantle, eventually causing magma to rise and erupt as lava.
Contents
MCQs
1. What role does magma play in volcanic eruptions?
A) It cools down the Earth’s core
B) It acts as a lubricant for tectonic plates
C) It rises and erupts as lava
D) It solidifies to form the Earth’s crust
Answer: C) It rises and erupts as lava
Explanation: Magma is molten rock beneath the Earth’s surface that, during a volcanic eruption, rises through the crust and erupts as lava.
2. What is NOT a factor in causing volcanic eruptions?
A) Increase in gas pressure within the magma
B) Decrease in the Earth’s magnetic field
C) Increase in temperature causing rocks to melt
D) Introduction of water into the magma
Answer: B) Decrease in the Earth’s magnetic field
Explanation: A decrease in the Earth’s magnetic field is not a factor in causing volcanic eruptions. Factors include gas pressure, temperature changes, and water introduction into the magma.
3. How does water contribute to volcanic eruptions?
A) By cooling down the lava rapidly
B) By increasing the pressure within the magma
C) By acting as a barrier to magma rise
D) By solidifying the magma instantly
Answer: B) By increasing the pressure within the magma
Explanation: Water can contribute to volcanic eruptions by being introduced into the magma, where it turns to steam, increases pressure, and can eventually lead to an eruption.
4. What is lava?
A) Water expelled from a volcano
B) Magma that has reached the Earth’s surface
C) A type of rock formed under high-pressure
D) Gases released during an eruption
Answer: B) Magma that has reached the Earth’s surface
Explanation: Lava is the term used for magma once it erupted onto the Earth’s surface.
Read More