Question

Where does the old seafloor go once new ones are made?

a) Slowly plunging beneath continental lithosphere along Earth's deep-ocean trenches.

b) Accumulating on the surface, forming new continents over time.

c) Dissolving into the Earth's mantle, contributing to the formation of new magma.

d) Dispersing into the atmosphere, leading to changes in global climate patterns.

Answer 1

Old seafloor is forced beneath continental lithosphere at deep-ocean trenches through the process of subduction. This results in the oceanic crust melting and integrating into convection currents, which helps balance the creation of new crust at rift zones.

Step-by-step explanation:

The old seafloor is subjected to the process of subduction, where one tectonic plate is forced beneath another. Specifically, the thinner oceanic plates can be subducted beneath the continental lithosphere at deep-ocean trenches. A prime example is the Japan trench along the coast of Asia.

During subduction, the plate is pushed into high-pressure, high-temperature zones in the upper mantle, eventually melting and getting recycled into a convection current that balances the material rising at rift zones.

Most of the rocks formed at divergent boundaries are igneous, with layers including ophiolites, which are often pushed to Earth's surface during the end of subduction. These stages of subduction lead to the oceanic lithosphere being uplifted with newly forming mountain belts.

Consequently, subducted oceanic crust is not simply lost; it becomes part of the geological recycling process, contributing to the continuous change of Earth's surface.