Final answer:
The Mid-Atlantic Ridge was formed by divergent plate boundaries where upwelling mantle currents cause tectonic plates to separate, and molten basaltic lava fills the gap to create new oceanic crust. The ridge is a physical manifestation of the plate tectonics processes that expand the Atlantic Ocean and record the Earth's magnetic field reversals.
Step-by-step explanation:
Formation of the Mid-Atlantic Ridge
The Mid-Atlantic Ridge is a massive mid-ocean ridge and an underwater mountain range that was formed by the divergent plate boundary located in the middle of the Atlantic Ocean. The formation process involves upwelling currents in the Earth’s mantle at the rift zones, where the tectonic plates pull apart from each other. As this happens, molten basaltic lava rises from beneath the Earth’s crust to fill the space created between the separating plates. This influx of basaltic material solidifies to create new oceanic crust, continually pushing the plates apart and allowing the ridge to grow.
Over time, the continued separation of the tectonic plates results in the expansion of the Atlantic Ocean. Additionally, along the Mid-Atlantic Ridge, volcanic activity extrudes material, and as the new crust cools and solidifies, it records the Earth’s magnetic field at the time of its formation. The alternating pattern of magnetic stripes on either side of the ridge provides evidence of the Earth's historical magnetic field reversals. This information, along with the knowledge of the spreading rate, can give us a historical record of the Earth's magnetic field changes over time.