Why in the News?

Mount Etna, Europe’s largest active volcano, has erupted sending ash, smoke, and rock fragments several kilometres into the sky.

Why do Volcanoes Erupt?

Magma Formation: Deep within Earth, high temperature and pressure melt rocks into magma.
Gas Expansion: Magma contains gases like water vapor, CO₂, and SO₂. As magma rises, the pressure drops, allowing these gases to form bubbles, increasing internal pressure.
Crustal Weaknesses: At tectonic boundaries or mantle plumes, cracks and faults in Earth’s crust provide pathways for magma to escape.
Eruption Mechanism:
- As pressure builds, magma is pushed upwards.
- If blocked, the gas expansion can explode through the crust, ejecting lava, ash, and gases.
Signals: If magma flow is suddenly stopped by solid rock, it may create low-frequency seismic waves (pre-eruption tremors).

Next Census to conclude by March 2027

Location: Situated on the east coast of Sicily, Italy, near the city of Catania.
Type: Mount Etna is a stratovolcano (also called a composite volcano), which is formed from layers of hardened lava, volcanic ash, and rocks.
Height: It stands at approximately 3,300 meters, making it the tallest volcano in Europe south of the Alps.
Recognition: Declared a UNESCO World Heritage Site in 2013, with documented volcanic activity for at least 2,700 years.
Eruption Record: Etna is almost constantly active. Notable eruptions have occurred in 1400 B.C., 1669, 2001, 2018, 2021, 2024, and 2025.
Volcanic Activity Style: Known for Strombolian and effusive eruptions, with occasional Plinian eruptions (rare and more explosive).

Nature of Eruption: The eruption is classified as either Strombolian or possibly Plinian, depending on interpretation:
- Strombolian Eruption: Characterized by moderate explosive bursts, caused by gas bubbles in magma suddenly bursting at the surface.
- Plinian Eruption: Some volcanologists suggest this classification due to the large ash column that may have reached the stratosphere.
Eruption Trigger: The eruption likely began due to pressure buildup from gas within the magma chamber, leading to collapse of the southeast crater and lava flows.

[UPSC 2024] Consider the following:

1. Pyroclastic debris

2. Ash and dust

3. Nitrogen compounds

4. Sulphur compounds

How many of the above are products of volcanic eruptions?

Options: (a) Only one (b) Only two (c) Only three (d) Only four*