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trench roll back
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A four-panel diagram illustrates the process of trench rollback and back-arc basin formation at an oceanic subduction zone. Each panel shows a cross-section of Earth's crust and upper mantle, with a subducting oceanic plate, overlying plate, trench, volcanic arc, and melted rock in the asthenosphere. The sequence demonstrates how the trench and volcanic arc migrate, rifting forms behind the arc, and a back-arc basin develops as plates move and new crust forms.
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trench roll back

marine geology
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A four-panel diagram illustrates the process of trench rollback and back-arc basin formation at an oceanic subduction zone. Each panel shows a cross-section of Earth's crust and upper mantle, with a subducting oceanic plate, overlying plate, trench, volcanic arc, and melted rock in the asthenosphere. The sequence demonstrates how the trench and volcanic arc migrate, rifting forms behind the arc, and a back-arc basin develops as plates move and new crust forms.
back-arc basin The trench “roll back” process of back-arc basin formation.

Trench roll-back is a geological process occurring at subduction zones where one tectonic plate slides beneath another. This phenomenon is typically observed along the western Pacific Ocean, where tectonic plates converge.1

As one plate subducts, it creates a trench. The process of back-arc spreading can occur behind the island arc formed by this subduction. This spreading involves magma rising and creating rifts in the crust, leading to the formation of spreading centers that widen the seafloor. In some cases, this widening forces the leading edge of the overriding plate to move seaward, causing the trench to "roll back" over the subducting plate. This contrasts with scenarios where the overriding plate acts as a sea anchor, remaining fixed and causing the trailing part of the plate to move in the opposite direction.1

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2 Britannica Sources
  1. plate tectonics - Subduction zones
  2. back-arc basin

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