340 likes | 815 Vues
The Atmosphere. The earth is surrounded by an envelope of gases known as the atmosphere. Nitrogen, oxygen and carbon dioxide are all parts of this mixture. Gases can be added and removed from the atmosphere. Plants take in carbon dioxide and produce oxygen
E N D
The earth is surrounded by an envelope of gases known as the atmosphere Nitrogen, oxygen and carbon dioxide are all parts of this mixture
Gases can be added and removed from the atmosphere • Plants take in carbon dioxide and produce oxygen • Volcanic eruptions add water vapor and ash • Cars both adds and removes gases
The atmosphere is composed of the following: • Nitrogen – (78%) enters the atmosphere when volcanoes erupt and when dead plants and animals decay • Oxygen – (21%) produced by plants • Other gases – (1-2%) Argon, carbon dioxide, methane, and water vapor
The atmosphere also contains many types of solid particles or atmospheric dust Water droplets condense around the pieces of dust to form rain
The atmosphere is pulled toward the Earth’s surface by gravity As a result, the atmosphere is denser at the surface than in higher elevations
The atmosphere is divided into four layers based on temperature • The Troposphere • The Stratosphere • The Mesosphere • The Thermosphere
The troposphere is the lowest layer of the atmosphere (18km above the surface) It’s the densest layer of the atmosphere and the temperature decreases as altitude increases
The stratosphere is the next layer in the atmosphere. (18km – 50km) The stratosphere contains the ozone layer – absorbs the Sun’s UV rays
The mesosphere is the coldest layer of the atmosphere The temperature has been recorded as low as –90 degrees Celsius
The thermosphere is the layer farthest from the surface and has the highest temperature (2000 C) Nitrogen and oxygen absorb harmful solar radiation such as X-Rays and gamma rays from space
Within the thermosphere, is an area called the ionosphere Particles of the ionosphere become electrically charged and can sometimes radiate energy as light - auroras
Energy from the sun is transferred in the Earth’s atmosphere by three mechanisms • Radiation – energy transfer across space • Conduction – energy transfer by direct contact • Convection – energy transfer by air currents
Solar energy reaches the Earth by radiation, passes through the atmosphere and heats the surface The heat from the surface heats the air molecules in the atmosphere causing them to rise
The heated air rises, cools and begins to sink, where it is reheated and rises again The continuous process of warm air rising and cool air sinking is called a convection current
The gases in the Earth’s atmosphere act like the glass in a car. They trap heat inside the atmosphere This is known as the Greenhouse Effect
The amount of greenhouse gases (carbon dioxide, water vapor and methane) in our atmosphere is small (less than 2%) To keep global temperatures at a reasonable level, the level of greenhouse gases must stay the same