Because Earth Sciences covers a lot of ground (pun intended) and nobody has the time or ability to do everything well and thouroughly. The field is very highly specialized in its subdivisions.
Specialities and subspecialities help us to delve deeper into the subject of earth science. It is equally important for us to understand the impacts of various areas.
<u>Explanation:</u>
Earth Sciences is a vast subject dealing with pollution, climate, oceans, energy resources, human impacts.
For us to act accordingly, it is essential to have a deeper look into the features.
There are specializations or subspecialities in each feature to be understood.
Scientists are working on each subspeciality to make informed decisions in order to avoid catastrophic failures and disasters as much as possible.
Disasters are unavoidable but minimizing the effects is what we can do.
The Moon doesn't make its own light, it just reflects the Sun's light as all the planets do. We see the Moon go through a changing cycle of phases each month due to its orbital motion around Earth and the changing geometry with which we view it.
A planet is an object that orbits the Sun in an elliptical orbit, has compounded its matter in a spherical shape and has cleared its orbit of other debris. While a dwarf planet also orbits the Sun, has compounded its matter in a spherical shape, but has not cleared its orbit of other debris.
