* Earth's Plates Move: The Earth's outer layer is made up of tectonic plates that constantly move. These plates can collide, separate, or slide past each other.
* Shifting Continents: Over millions of years, the movement of these plates has caused continents to shift their positions drastically. What was once ocean floor might have been pushed up to form land, carrying with it the fossils of marine animals that lived there.
* Sedimentation: As the ocean floor is uplifted, layers of sediment (sand, mud, etc.) are deposited on top, eventually becoming the sedimentary rock we see today.
In short: Fossils of ocean animals found in land-based sedimentary rock are a strong piece of evidence for the theory of continental drift, demonstrating that Earth's surface is not static but constantly changing over geological timescales.
