What is the role of magma in understanding sea-floor spreading?

Correct answer: Magma rises, cools, and forms new oceanic crust

The direct answer is A: magma rises, cools and forms new oceanic crust. At a mid-ocean ridge, tectonic plates move apart. Hot material from below rises into the opening. When magma reaches or approaches the ocean floor, it loses heat, solidifies and becomes new basaltic oceanic crust. Continued upwelling and cooling push older crust away from the ridge, producing seafloor spreading. This process also helps explain symmetrical magnetic stripes on both sides of many ridges, because minerals record Earth’s magnetic direction as the lava cools. Option A is correct because it gives the essential sequence: rising magma, cooling, and crust formation. Option B is wrong because magma does not remove all seawater; water remains in the ocean, although volcanic activity can interact with it locally. Option C is wrong because clouds form mainly through atmospheric water vapour and weather processes, not because magma only makes clouds. Option D is wrong because magma movement and related mantle processes help plates move; they do not keep every plate fixed. Magma does not create all crust everywhere, but at divergent boundaries it is central to new oceanic crust formation. Memory cue: ridge opens, magma rises, lava cools, new crust spreads.