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What Happens Inside a Volcano Before It Erupts?
火山喷发前，内部究竟发生了什么？
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Magma rises from deep underground when pressure builds due to gas expansion and tectonic movement.
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Dissolved gases like water vapor, CO₂, and sulfur dioxide separate from magma as pressure drops near the surface.
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These expanding bubbles increase internal pressure until the rock above can no longer contain them.
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Seismic monitors detect tiny earthquakes caused by magma fracturing surrounding crustal rock.
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Ground swelling occurs as magma chambers fill, measurable by GPS and satellite radar interferometry.
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Gas emissions spike days or weeks before eruptions, especially sulfur dioxide and carbon dioxide ratios.
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Changes in groundwater temperature, chemistry, and flow also signal underground thermal and chemical shifts.
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Volcanologists combine all these clues to issue timely warnings, though precise timing remains challenging.
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Not all magma reaches the surface — sometimes it cools underground, forming intrusive igneous rock instead.
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Each volcano has its own ‘personality’, shaped by magma composition, structure, and regional geology.