十万个为什么·科学启蒙30篇（2）
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Why Do Volcanoes Erupt After Being Quiet for Years?
为什么火山在沉寂多年后会突然喷发？
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Molten rock called magma rises slowly from deep inside Earth’s mantle.
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Pressure builds up beneath the surface when magma cannot escape through solid rock.
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Gas bubbles trapped in the magma expand as it rises, increasing pressure further.
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When pressure exceeds the strength of the overlying rock, an eruption occurs.
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Some volcanoes stay quiet for centuries while magma slowly accumulates underground.
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Scientists monitor earthquakes, ground swelling, and gas emissions to predict eruptions.
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The type of eruption depends on magma thickness and gas content.
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Explosive eruptions happen when thick, sticky magma traps gas until it bursts.
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Quiet eruptions occur when thin, runny magma lets gas escape easily.
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Volcanic ash can travel thousands of miles and affect global weather patterns.