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Section 2.1 Earth's atmosphere in context

It is important to recognize that the atmosphere is not isolated from other Earth systems, and we can consider interactions between the and geosphere, hydrosphere, atmosphere, biosphere.

The geosphere is the solid rocky mass of the Earth and provides the lower boundary to the atmosphere and oceans (which cover 71% of the area of the Earth). As a whole, planet Earth has a average radius of 6371 km and a mass of 6x1024 kg. This provides clues to its bulk composition: an iron core surrounded by a large silicate (rocky) mantle.

The hydrosphere consists of the water inventory of the Earth, making up about 0.03% of the Earth's mass. The water of the Earth is distributed into 97% oceans and 3% freshwater; only about 0.001% of the Earth's water is present in the atmosphere. Of the freshwater inventory, less than 1% is found in surface lakes and rivers; most freshwater is present in glaciers (70%) or groundwater (30%).

The atmosphere is a thin layer of air (a mixture of different gases) above the Earth's surface. The mass of atmosphere is about one-millionth of the total mass of the Earth. The atmosphere is also relatively thin, and over 99% of the atmosphere's mass is found below an altitude of 30 km (19 miles)

The biosphere consists of all plant and animal life on the planet. The biosphere is closely connected to the atmosphere through the processes of photosynthesis and respiration.

The relative masses of each of these systems is summarized in the table below:

Table 2.1.1. Earth systems
System Mass (kg)
Geosphere \(6.0\times 10^{24}\)
Hydrosphere \(1.7\times 10^{21}\)
Atmosphere \(5.0\times 10^{18}\)
Biosphere \(1.0\times 10^{16}\)