Hayli Gubbi eruption: Why some volcanoes eject lava, others spew smoke and ash, Pg17

Key Highlights:

• The Hayli Gubbi volcano in northeastern Ethiopia erupted on Sunday after 12,000 years of dormancy.
• The eruption involved plumes of ash and gases, not molten lava.
• The nature of volcanic eruptions depends on the viscosity and dissolved gas content of the magma.

Detailed Insights:

• Silica content in magma determines its viscosity; low silica results in fluid magma and gentle eruptions.
• High silica magma is stickier, trapping volatiles and leading to explosive, ash-heavy eruptions.
• Explosive eruptions occur when accumulated gas-rich volatiles reach a breaking point, ejecting fragmented magma (tephra) instead of lava.

Scientific/Technical Concepts Involved:

• Magma: Molten rock beneath the Earth's surface.
• Viscosity: A fluid's resistance to flow or "stickiness".
• Volatiles: Dissolved gases in magma that can cause explosive eruptions.
• Tephra: Fragmented magma ejected during an explosive volcanic eruption.