I think it it a fragment by think I mean I think I know the sentence
Theory of plate tectonics states that Earth's surface the upper mantle an crust, was once made up of enormous rock plates that broke into smaller pieces approximately 300 million years ago and These smaller broken plates form more fluid rock surface in the mantle. as Time passed the plates move and morph into natural land boundaries. This explains natural land phenomena, such as earthquakes and tsunamis.
A phrase that looks like a verb, but can actually function as if it were an adjective. It can modify a noun in the same sentance.
