Here's why:

* Basaltic Volcanism: Mid-ocean ridges are where new oceanic crust is formed. This process involves the upwelling of magma from the Earth's mantle, which is primarily composed of basalt. This magma erupts on the ocean floor, solidifying to create new oceanic crust.

* Seafloor Spreading: The process of seafloor spreading occurs at mid-ocean ridges. As new oceanic crust is formed, it pushes older crust away from the ridge, causing the seafloor to spread apart. This is evidenced by the magnetic striping pattern on the ocean floor, which reflects the changing polarity of the Earth's magnetic field over time.

Let me know if you have any other questions!