A large area of flat land, that is at a high altitude is called a plateau. An excellent example of a plateau is Tibet.
Renewable energy is energy that doesn't run out.Examples of these are wind and water. Nonrenewable energy sources are things like oil and coal—fossil fuels, because once they're gone, we're not getting them back. but we'll always have wind and water.
There is really nothing to know. All you have to use is context clues and common sense. We know some synonyms for direct are manage and handle. Indirect means not direct, right? And we can't handle or manage earth's interior (core), right? Therefore, the study of earth's interior is an example of indirect observation because we cannot directly manage it.