Scientists generally divide our little blue world into four separate yet overlapping spheres. These spheres are the lithosphere, the atmosphere, the biosphere, and the hydrosphere.
Each of these spheres consist of unique properties that separate them from the others. However, as I am sure you have noticed, there is no distinct boundary or border between them. The atmosphere extends downward into the soil, into caves and rocks, and even into water. The hydrosphere, which consists of all the water on Earth, extends high into the atmosphere and deep into the lithosphere, or rocks and soil. The lithosphere often gets carried upward into the atmosphere in the form of dust, and so forth.
In this chapter we will explore the Earth’s hydrosphere. The hydrosphere plays a very important role in the evolution of life, as well as in weather and erosion.