Translations of Encyclopedia about Geology

When discussing the preservation of our earth, two major issues are always in the forefront: the destruction of the vital ozone layer and the question of the greenhouse effect, which may be causing the increase of temperature of the atmosphere.

Ozone is an unstable gas (rather rare). It is a toxic form of oxygen. It consists of three atoms of oxygen in one molecule, while in the common molecule of oxygen there are only two atoms. Ozone is present in the entire atmosphere up to the altitude of approximately 50 kilometres. The layer containing the highest concentration of ozone (the ozone layer) is situated in the lower geographical latitudes at approximately 25 kilometres above the point zero (sea level). The altitude of the ozone layer decreases in the direction of polar regions.

By means of photochemical reaction, the short-wave part of ultraviolet rays changes oxygen into ozone. In this way, the majority of cell-damaging ultraviolet light is absorbed.

The use of chloro-fluoro-carbohydrates in sprays and manufacture of foams causes long-term damage of the protective ozone layer. The reason is, that when these gases are released, they rises very slowly into the atmosphere. There, they are dissolved by the ultraviolet light into free atoms of chlorine. They interact with ozone and destroy it. When the ozone layer is damaged, ultraviolet light penetrates to the surface of the earth. Chloro-fluoro-carbohydrates have a very long life and may continue destroying the ozone layer during many years.

This destructive process is specially noticeable at lower temperatures. A considerable decrease in the ozone layer was registered several years ago at the south pole during the winter season. This decrease is called the ozone hole. More than half of the ultraviolet rays pass through the hole. The consequence of this energy-releasing process is the release of heat. In the meantime, this effect emerged also over the north pole. In Antarctica, when at the end of the polar night the atmosphere gradually warms up again, air from the lower latitudes, rich in ozone, streams in and "fills up" the ozone hole.

In autumn of the year 2000, the hole in the ozone layer over Antarctica increased to 29 million cubic kilometres, which is four times the size of Australia. According to the information of New Zealand Antarctic stations, this increases the risk of exposure to cancer-producing ultraviolet light for the population of the southern hemisphere as never before. Antarctica as such is also threatened, because its very sensitive ecosystem may be quickly destroyed by this situation.

While the ozone in the stratosphere is being depleted, in the lower layers of the atmosphere, i.e., in the troposphere, the amount of ozone is on the increase as a result of the emissions of the automobiles (nitrogen and sulfur oxides). However, this does not help balance the decreased amounts of ozone in the stratosphere.

Even assuming that there will be a complete halt in use of the chloro-fluoro-carbohydrates, it must be taken into consideration that their damaging effects will increase. In the higher latitudes, people must take precautions and protect themselves against the ultraviolet light of the sun.

In most cases, the term "greenhouse effect" is synonymous with a negative, man-made climate change. However, without a natural greenhouse effect, the life on our planet would be impossible. The earth would remain hostile to life.

Sunlight easily passes into a greenhouse and warms it up. However, the heat cannot easily escape. That way, the heat accumulates, and that is very similar to what is going on in the atmosphere that surrounds us. It is made up of different gases: 78.1 percent of nitrogen, 21 percent of oxygen, 0.9 percent of argon, 0.03 percent of carbon dioxide, and traces of noble gases.

Fifty percent of sunlight easily reach the earth's surface, which is heated by this sunlight. The heated earth also irradiates heat. This heat, analogous to the heat of a greenhouse, cannot easily escape through the atmosphere into the universe. It is held in the atmosphere, mostly by water vapour and carbon dioxide. These two gases absorb the heat and transfer it back to the earth.

In the last few decades, people have caused the increase of the greenhouse effect. Industry, transportation and agriculture, all share in the additional amounts of the greenhouse gases being produced. These gases prevent the heat to escape into the universe, and reflect it back to the earth.

The more greenhouse gases there are, the more heat stays within the earth-atmosphere cycle. Carbon dioxide is not the only gas that increases the temperature in the atmosphere. There is also methane, which is released when forests are cleared by burning. It is also released by landfills and by many ruminants, such as beef cattle, sheep and goats. Carbon dioxide is exhaled by people and animals. It also escapes from volcanoes and is released by burning of fossil fuels. The ozone of the lower layers of the atmosphere is also one of the greenhouse gases.