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 answer is: waterfalls can usually be found wherever there is lots of erosion or where there is steepness in the river's channel.
Answer:
Tropical wet climate regions are near the equator on several continents
It became a US Territory.
