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.
Answer:
They are classified by altitude and the patterns they form.
Explanation:
Clouds are classified by their altitude in the troposphere. Some clouds are found beyond the troposphere. The classification as surface level, low, middle, high and multi-level. The multi-level are massive storms clouds, known as cumulonimbus that rise from the low altitudes to the top of the troposphere. A surface cloud can be classified as fog or mist. The low level can have stratus clouds. The middle level can contain nimbostratus and the high level can contain cirrus clouds. The names are given based on their altitude but the way in which their form.
If you could dig a tunnel right through the Earth you could theoretically free-fall to the centre of our planet in just eighteen minutes. You can’t, of course: such a tunnel would have to tolerate temperatures as high as the surface of the Sun and pressures three and a half million times greater than those at the Earth’s surface.
