Which phenomenon causes arc volcanism when an oceanic plate subducts beneath a continental plate?

💡 Explanation

When an oceanic plate subducts, hydration-induced melting occurs because water released from the subducting plate lowers the mantle's melting point, resulting in magma formation and arc volcanism. Therefore, hydration melting is the main cause, rather than decompression, friction, or radiogenic heating which are less significant factors in this process.

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• Which process triggers a Plinian eruption when magma viscosity and gas content are critically high?
• Which mechanism increases the explosive potential when magma's viscosity increases in a volcano?
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