These four subsystems are called "spheres." Specifically, they are the "lithosphere" (land), "hydrosphere" (water), "biosphere" (living things), and "atmosphere" (air). Each of these four spheres can be further divided into sub-spheres
The Equator actually gets less hours of daylight than the other latitudes
By studying seismic waves
1. gravity keeps the water moving downward or just in general
2. the water has to move across the surface for so long till eventually it just erodes away.
those are the only two i know sorry.