Answer:

• Plate tectonics is the theory that Earth's land masses are in constant motion. The realization that Earth's land masses move was first proposed by Alfred Wegener, which he called continental drift. ... But the continents actually are shifting, very slowly, relative to one another.

• When filled with water, these basins form the planet's oceans.The lithosphere is the outermost mechanical layer, which behaves as a brittle, rigid solid.