Source regions of global air masses.
Water vapor generated through surface evaporation is transported by circulatory patterns in the atmosphere. When atmospheric conditions permit an uplift of warm, humid air, this water condenses and settles to the surface as precipitation. Most of the water is then transported back to lower elevations by river systems, usually returning to the oceans or being deposited into lakes. This water cycle is a vital mechanism for supporting life on land, and is a primary factor in the erosion of surface features over geological periods. Precipitation patterns vary widely, ranging from several meters of water per year to less than a millimeter. Atmospheric circulation, topological features and temperature differences determine the average precipitation that falls in each region.
Upper atmosphere
Above the troposphere, the atmosphere is usually divided into the stratosphere, mesosphere, and thermosphere. Each of these layers has a different lapse rate, defining the rate of change in temperature with height. Beyond these, the exosphere thins out into the magnetosphere (where the Earth’s magnetic fields interact with the solar wind). An important part of the atmosphere for life on Earth is the ozone layer, a component of the stratosphere that partially shields the surface from ultraviolet light
This view from orbit shows the full Moon partially
obscured by the Earth’s atmosphere. NASA image.
Due to thermal energy, some of the molecules at the outer edge of the Earth’s atmosphere have their velocity increased to the point where they can escape from the planet’s gravity. This results in a slow but steady leakage of the atmosphere into space. Because unfixed hydrogen has a low molecular weight, it can achieve escape velocity more readily and it leaks into outer space at a greater rate. For this reason, the Earth’s current environment is oxidizing, rather than reducing, with consequences for the chemical nature of life which developed on the planet. The oxygen-rich atmosphere also preserves much of the surviving hydrogen by locking it up in water molecules.
Biosphere
A planet that can sustain life is termed habitable, even if life did not originate there. The Earth provides the (currently understood) requisite conditions of liquid water, an environment where complex organic molecules can assemble, and sufficient energy to sustain metabolism. The distance of the Earth from the Sun, as well as its orbital eccentricity, rate of rotation, axial tilt, geological history, sustaining atmosphere and protective magnetic field all contribute to the conditions necessary to originate and sustain life on this planet.
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The planet’s life forms are sometimes said to form a “biosphere”. This biosphere is generally believed to have begun evolving about 3.5 billion years ago. Earth is the only place in the universe where life is known to exist. Some scientists believe that Earth-like biospheres might be rare.
The biosphere is divided into a number of biomes, inhabited by broadly similar plants and animals. On land primarily latitude and height above the sea level separates biomes. Terrestrial biomes lying within the Arctic, Antarctic Circle or in high altitudes are relatively barren of plant and animal life, while the greatest latitudinal diversity of species is found at the Equator.
III. Answer the questions:
1. What is hydrosphere?
2. Is Challenger Deep of the Mariana Trench in the Pacific Ocean the deepest underwater location?
3. What is average depth of the oceans?
4. What kinds of water do we have on our planet?
5. What can cause significant weather shifts?
6. Oxygen, nitrogen and carbon dioxide are the main gases in the atmosphere, are not they?
7. How many atmospheric functions do you know? Make a list of them.
8. What is greenhouse effect?
9. Where are the three-quarters of the atmosphere’s mass located?
10. What can you tell about the troposphere?
11. What mechanism is vital for supporting life? Describe it.
12. How many layers of upper atmosphere do we have? Describe them.
13. What are the main conditions for life sustaining?
14. What is biosphere?
IV. Do you agree or disagree with the following statements? Explain why.
1. The Earth’s hydrosphere consists only of the oceans.
2. The majority of the fresh water, about 68.7%, is currently in the form of ice.
3. Hydrosphere has no influence on the world’s climate.
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