Semeru erupts: What causes volcanic eruptions? Why are some more explosive?, Pg16

Key Highlights:

• Mount Semeru, one of Indonesia's 120 active volcanoes, erupted on Wednesday, ejecting hot volcanic ash and debris.
• Volcanoes erupt due to the movement of heat beneath the Earth's surface, where rocks melt into magma.
• The explosivity of an eruption depends on the magma's composition: thin magma allows gas escape, while thick magma traps gas, leading to explosions.

Detailed Insights:

• Deep within the Earth, intense heat causes rocks to melt into magma, a thick, flowing substance that is lighter than surrounding rock.
• Magma rises and collects in chambers near the surface, increasing pressure on the surrounding rock, eventually pushing through cracks and vents, resulting in a volcanic eruption.
• Eruptions involving thick, sticky magma are more explosive because the gas cannot escape, causing the magma to blast into the air and solidify into tephra of varying sizes.

Scientific/Technical Concepts Involved:

• Magma: Molten rock beneath the Earth's surface.
• Lava: Magma that has erupted onto the Earth's surface.
• Tephra: Solid material ejected during a volcanic eruption.