Air+Pressure,+Layers+of+the+Atmosphere

Air Pressure
=== The atmosphere has weight because of Earth's gravity.As a result of this weight, the atmosphere exerts pressure. Air pressure is the force exerted by the weight of a column of air on a surface. Air pressure changes with altitude. The atmosphere is denset near Earth's surface and becomes less dense as altitude increases. As altitiude increases, air pressure and density decrease. about half of the total mass of the athmosphere is bellow an altitude of 5.6 kilometers. when Hillary and Tenzing climbed Mount Everst, they climbed, the air became less dense. Hillary had trouble breading without an oxygen mask because there were many fewer oxygen molecueles per cubic meter of air at the summit than at sea level.Scientists measure air pressure with an instrument called a barometer. As air pressure increases, the column of mercry in the barometer rises. as air pressure decreases, the column of mercury falls. ===

The //Troposhere// is the loswest layer of the Earth's atmosphere. The layer has most of the water vapor. In the Troposphere, temperatre denerally decreases as altitude increases.
=== The //stratosphere// extendeds from an altitidude of about 12 kilometers to 20 kilimeters. Above that height, temperture increases as altitude increases. The upper stratosphere is warmer than the lower stratosphere because of the ozone layer. Ozone layer is a region of high ozone concentration. === === The //mesosphere// the layer above the stratosphere. It begins at an altitude of about 50 kilometers and extends to about 80 kilometers. In the mesosphere, temperature decreases as altitude increases. The air in the mesosphere is very thin! Studies show that in this layer the air moves at a speed of 320 kilometers per hour. Most meteroriods that enter the atmospher burn up in the mesosphere. === === The //thermosphere// begins at an altitude of about 80 kilometers and extends outward into space.There are no boundary marks in the atmosphere. In the thermosphere temperature increases rapidly with altitude. === === The //ionosphere// is not a disinct layer of the atmosphere. It is a region of charged particles, or ions that overlaps the lower thermosphere. One of nauture's most spectaular displays occurs in the ionosphere. An aurora, a colorful display of lights in the sky, produced when charged particles the sun are attracted to the Earth's magnetic poles. ===

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[] === In conclusion air pressure is a force of air. The four layers of the atomosphere are Troposphere ,which is the lowest layer. The stratosphere which is 12 to 50 kilometers above altitude. The mesosphere begins at an altitude of 50-80 kilometeres. The thermosphere is above 80 Km and the Ionosphere is a region! ===

__//**Emily and Marcos**//__ __//**10-12-10**//__ __//**period 7**//__