Why do volcanoes near subduction zones often erupt explosively?
Quick Answer
As one plate sinks beneath another, water and gases help melt the mantle and create sticky, silica-rich magma. That magma traps gas, so pressure builds until it erupts violently.
The Full Story
At subduction zones, an oceanic plate descends into the mantle and releases water from its minerals. This lowers the melting point of overlying rock and helps generate magma that is often high in silica and more viscous than basaltic lava. Thick magma traps volcanic gases, allowing pressure to build inside the conduit. This is why many arc volcanoes, including those in the Andes and Japan, can produce explosive eruptions and towering ash columns.
Key Facts
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"Why sinking plates make some of the world’s most explosive volcanoes"
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