What is the theory of plate tectonics best described as?

The theory of plate tectonics is best described as the idea that Earth's outer shell is divided into several large, rigid plates that float on a semi-fluid layer of the mantle beneath them. This theory explains how these tectonic plates move and interact with each other at their boundaries, leading to various geological phenomena such as earthquakes, volcanic activity, and mountain building. The movement of these plates is driven by forces such as mantle convection, slab pull, and ridge push, making it a foundational concept in understanding the dynamic nature of Earth's surface.

Other options do not accurately reflect the core principles of the theory. For instance, while the formation of the moon is an interesting topic, it is not related to the movements of Earth's tectonic plates. Similarly, discussing the evolution of species, such as that of fish, falls under biological sciences and is unrelated to geological processes. Lastly, while predicting tectonic plate movements is a significant aspect of the theory, it is not the sole purpose or description of the theory itself. The essence of plate tectonics encompasses the interaction and behavior of the plates rather than limiting it to mere movement predictions.