• TROPOSPHERE This is the layer of the atmosphere closest to the Earths surface, extending up to about 10-15 km above the Earths surface. It contains 75% of the atmospheres mass. The troposphere is wider at the equator than at the poles. Temperature and pressure drops as you go higher up the troposphere. The Tropopause: At the very top of the troposphere is the tropopause where the temperature reaches a (stable) minimum. Some scientists call the tropopause a "cold trap" because this is a point where rising water vapor cannot go higher because it changes into ice and is trapped. If there is no cold trap, Earth would loose all its water! The uneven heating of the regions of the troposphere by the Sun causes convection currents and winds. Warm air from Earths surface rises and cold air above it rushes in to replace it
• STRATOSPHERE This layer lies directly above the troposphere and is about 35 km deep. It extends from about 15 to 50 km above the Earths surface. The lower portion of the stratosphere has a nearly constant temperature with height but in the upper portion the temperature increases with altitude because of absorption of sunlight by ozone. This temperature increase with altitude is the opposite of the situation in the troposphere.• The Ozone Layer The stratosphere contains a thin layer of ozone which absorbs most of the harmful ultraviolet radiation from the Sun. The ozone layer is being depleted, and is getting thinner over Europe, Asia, North American and Antarctica --- "holes" are appearing in the ozone layer.
• The Mesosphere The mesosphere is the third layer in the atmosphere. It is extending from 50 to 80 km above the earth’s surface. The temperature drops when you go higher, like it does in the troposphere. It can get down to - 90°C in the mesosphere. Thats the coldest part of the atmosphere!
• The mesosphere starts is on top of the stratosphere. Sometimes you can see the mesosphere by looking at the edge of a planet (like the picture to the left).
• THERMOSPHERE The thermosphere extends from 80 km above the Earths surface to outer space. The temperature is hot and may be as high as thousands of degrees as the few molecules that are present in the thermosphere receive extraordinary large amounts of energy from the Sun. However, the thermosphere would actually feel very cold to us because of the probability that these few molecules will hit our skin and transfer enough energy to cause appreciable heat is extremely low.
The thermosphere extends from 80km above the Earths surface. Thethermosphere is the fourth layer of theEarths atmosphere. It is found above themesosphere. The air is really thin thathigh up. The temperature changes withthe solar activity. If the sun is active,temperatures in the thermosphere canget up to 1,500°C or higher! The Earths thermosphere alsoincludes the region calledthe ionosphere.
• The Exosphere Very high up, the Earths atmosphere becomes very thin. The region where atoms and molecules escape into space is referred to as the exosphere. The exosphere is on top of the thermosphere.
The exosphere is the uppermost layerof Earths atmosphere. In the exosphere,an upward travelling molecule moving fastenough to attain escape velocity canescape to space with a low chance ofcollisions; if it is moving below escapevelocity it will be prevented from escapingfrom the celestial body by gravity. In eithercase, such a molecule is unlikely to collidewith another molecule due to theexospheres low density.
• Ozone depletion Is the thinning of the ozone layer. It is caused by the burning of the plastics, smoke coming from factories and vehicles, air conditioners and refrigerators that is filled with CFCs. it affects the people health.
see in thepicture...th e ozone hole is getting bigger every several
• It is the heating of the earth and caused by;• The Greenhouse Effect Heat from the Sun warms the Earths surface but most of it is radiated and sent back into space. Water vapor and carbon dioxide in the troposphere trap some of this heat, preventing it from escaping thus keep the Earth warm. This trapping of heat is called the "greenhouse effect".
• However, if there is too much carbon dioxide in the troposphere then it will trap too much heat. Scientists are afraid that the increasing amounts of carbon dioxide would raise the Earths surface temperature, bringing significant changes to worldwide weather patterns ... shifting in climatic zones and the melting of the polar ice caps, which could raise the level of the worlds oceans.