Final answer:
The best support for the model of plate tectonics is that oceanic crust is continuously formed at divergent plate boundaries. This occurs through the cooling and solidification of basaltic magma, which corroborates the dynamic and recycling nature of Earth's crust inherent to plate tectonics.
Step-by-step explanation:
The statement that best supports the model of plate tectonics is, "It is continuously being formed at divergent plate boundaries." This is because the oceanic crust is made up of basalt, which is a type of mafic rock formed from the cooling of volcanic lava. This process takes place at divergent boundaries found in areas like the mid-Atlantic ridge, where new crust is generated as tectonic plates move apart.
In contrast, oceanic crust is thinner and denser than continental crust, which is primarily composed of granite. Since oceanic crust is denser, it can be readily subducted beneath continental crust at convergent plate boundaries, leading to its destruction in the mantle. This subduction process, often marked by ocean trenches, results in the recycling of old crust into the mantle, maintaining a balance between crust creation and destruction. Therefore, the continuous formation of oceanic crust at divergent boundaries and its subsequent subduction at convergent boundaries confirms the dynamic nature of Earth's lithosphere, as explained by plate tectonics.