Characteristics of the Environment - Field Sampling: Principles and Practices in Environmental Analysis - page 24

2.1. PARTS OF THE ENVIRONMENT
At first glance it seems obvious that there are several parts to the environment. There is
the atmosphere, which is the gaseous layer around the Earth. It extends from the Earth's
surface to space, which is often accepted to be 80 km (50 miles) above the surface. The
hydrosphere includes all bodies of water covering the Earth's surface. It is variable in
depth, depending on the underlying lithosphere. The lithosphere is the solid portion of the
Earth. It is not only the dry portion of the Earth's surface, which sticks up above oceans,
lakes, streams, and rivers, but also the solid portion underlying bodies of water.
Layers of different characteristics are common in all parts of the environment. (See
Figure 2.1.) It is not immediately obvious that the atmosphere and hydrosphere are
composed of various fluid layers, but they are. On the other hand, examples of layers in
the lithosphere are easily observed. Roads that are cut through mountainsides expose
observable layers of both rock and soil.
FIGURE 2.1 Layering in the atmosphere, hydrosphere, and lithosphere. CD is
cold, light water, while WL is warm, dense water.
2.1.1. The Atmosphere
There are different ways of looking at the layers in the atmosphere. In the older