How do plate tectonics form volcanic chains?

Volcanic chains, specifically volcanic arcs, form above subducting tectonic plates where an oceanic plate slides beneath an adjacent plate. As the subducting plate sinks into increasing pressure and temperature, trapped water and volatiles break down and lower the mantle's melting point. This melted magma ascends to create a belt of volcanoes parallel to the oceanic trench.

What we know

• Volcanic arcs form in belt shapes above subducting oceanic tectonic plates and typically parallel an oceanic trench, while volcanoes can also form where tectonic plates converge or diverge. [2, 3]
• The subducting oceanic plate releases water from hydrous minerals like micas, amphiboles, and serpentines due to increasing pressure and temperature at depth. [2]
• Released water and volatiles lower the melting point of the mantle, generating magma that ascends to form volcanoes. [2]
• Intraoceanic arcs form when oceanic crust subducts beneath other oceanic crust, while continental arcs form when oceanic crust subducts beneath continental crust. [2]

Where to go next

• compared withWhat is the difference between a volcanic arc and a hotspot chain?
• how it workedHow do intraoceanic arcs form?
• a case in pointWhat is the Central America Volcanic Arc?
• the bigger pictureHow do tectonic plates interact at convergent boundaries?
• how we knowWhat was the Farallon plate?
• an unexpected connectionHow do ancient sinking ocean plates build up continents?Plates subducting to form volcanic chains can simultaneously transport and accrete exotic crust fragments to build up continental landmasses.

Sources

• [1]volcanic arc (Wikidata Q13426043) · CC0 1.0
• [2]Volcanic arc · CC BY-SA 4.0
• [3]Volcano · CC BY-SA 4.0
• [4]Farallon plate · CC BY-SA 4.0
• [5]Central America Volcanic Arc · CC BY-SA 4.0