Whenever volcanic eruption occurs______?

Analyze the question: It asks what happens whenever a volcanic eruption occurs, so we need the one outcome that is always true of an eruption.

Concept: A volcano is an opening in the Earth's crust through which materials from deep inside the Earth escape. During an eruption, pressure built up beneath the surface is released, forcing out:

• Molten rock (magma, called lava once it reaches the surface)
• Gases (steam, carbon dioxide, sulphur dioxide, etc.)
• Solid materials (ash, cinders, volcanic bombs)

Checking each option:

• A. A new flat surface emerges: Not generally true. Eruptions usually build cones or mountains. Flat lava plateaus form only in special cases (fissure eruptions), so this is not what happens every time.
• B. Residual mountains are formed: Residual mountains are left behind by long-term erosion of higher land (e.g. inselbergs). They are not formed by eruptions.
• C. Overthrust fold is formed: Overthrust folds come from intense compressional forces in folding/faulting (tectonic movements), not from volcanic activity.
• D. Gases and molten magma are ejected: This is the defining feature of every volcanic eruption. ✔

Exam tip: Link each landform to its process:

• Volcanic eruption → gases, lava, ash ejected
• Folding → fold mountains, overthrusts
• Erosion → residual mountains

When a question says "whenever," choose the universal, defining characteristic rather than an occasional result.