Final answer:
Mid-ocean ridges are long, underwater mountain ranges where new sea floor is created by the eruption of magma onto Earth's surface at diverging plate boundaries.
Step-by-step explanation:
The long mountain belts that divide the sea floor and generate new sea floor as magma rises and erupts onto Earth's surface are known as mid-ocean ridges. These are long undersea mountain ranges formed by lava rising from Earth's mantle at plate boundaries. Mid-ocean ridges are significant as they are regions where new oceanic crust is formed as molten rock or basaltic lava rises from below to fill the space between diverging tectonic plates.
This process occurs along rift zones, with the Mid-Atlantic Ridge being a well-known example. In contrast, a subduction zone is where two plates come together, and one is thrust beneath the other, leading to the destruction of old crust and its recycling into the mantle, often marked by ocean trenches like the Japan Trench.