Answer:
The formation of new crust primarily occurs through a process called seafloor spreading at mid-ocean ridges. Here are the key steps involved:
1. **Magma Upwelling:** Beneath mid-ocean ridges, magma rises from the mantle due to partial melting. This creates a magma chamber below the Earth's surface.
2. **Magma Intrusion:** The magma then intrudes into the overlying crust, leading to the formation of a shallow magma chamber.
3. **Crustal Rifting:** The pressure from the upwelling magma causes the crust to crack and pull apart along the mid-ocean ridge. This process is known as crustal rifting.
4. **Magma Extrusion:** As the crustal plates separate, magma from the magma chamber rises to the surface, solidifies upon contact with cold seawater, and forms new oceanic crust.
5. **Cooling and Solidification:** The extruded magma cools rapidly, solidifying into basaltic rock, which becomes part of the oceanic crust.
This cycle of seafloor spreading continually adds new crust to the Earth's surface, contributing to the dynamic nature of tectonic plate movements.
