Continental drift and seafloor spreading are two related theories that describe the movement of the Earth's lithosphere. Continental drift is the theory that the continents have moved over time, while seafloor spreading is the theory that the ocean floor is created at mid-ocean ridges and moves away from these ridges as it ages.

Continental drift and seafloor spreading are both supported by a number of lines of evidence, including:

* The fit of the continents: The continents fit together like pieces of a puzzle, suggesting that they were once part of a single landmass.

* The distribution of fossils: Fossils of the same plants and animals have been found on different continents, even though these continents are now separated by oceans. This suggests that the continents were once connected and that the plants and animals were able to migrate between them.

* The age of the ocean floor: The ocean floor is younger near the mid-ocean ridges and older away from the ridges. This is consistent with the theory that the ocean floor is created at mid-ocean ridges and moves away from these ridges as it ages.

Continental drift and seafloor spreading are important theories that have revolutionized our understanding of the Earth's history. They have also helped to explain a number of geological phenomena, such as the formation of mountain ranges, volcanoes, and earthquakes.