1. Mantle Convection: The Earth's mantle is a layer of hot, semi-solid rock. Heat from the Earth's core causes convection currents within the mantle, where hot, less dense material rises, and cooler, denser material sinks.
2. Divergent Plate Boundaries: At divergent plate boundaries, where tectonic plates move apart, the rising convection currents bring hot magma from the mantle to the surface. This magma erupts through fissures, creating new oceanic crust.
3. Mid-Ocean Ridges: As the magma cools and solidifies, it forms a new seafloor. This process creates mid-ocean ridges, underwater mountain ranges that mark the boundaries where new crust is being formed.
4. Seafloor Spreading: As new oceanic crust is created at the mid-ocean ridges, the older crust is pushed away from the ridge, like a conveyor belt. This process is called seafloor spreading.
5. Magnetic Stripes: As the Earth's magnetic field flips over time, the new oceanic crust records these changes. This creates alternating stripes of normal and reversed magnetic polarity on the seafloor, providing evidence for seafloor spreading.
In summary, the key driver of seafloor spreading is the heat from the Earth's core that fuels the convection currents in the mantle. These currents create new crust at divergent plate boundaries, pushing the older crust away and expanding the ocean floor.
