Earth’s surface water triggers the transformation of the core’s outer layer through a process called subduction. When oceanic plates collide with continental plates, the denser oceanic plate is forced beneath the continental plate into the mantle. As the subducted plate descends, water is released, causing melting in the mantle above. This molten material then rises and interacts with the overlying mantle, influencing the composition and dynamics of Earth’s outer core, contributing to geological processes, and shaping the planet’s structure.