Atmosphere. Earth's atmosphere is a mixture of gases, solids, and liquids that surround the planet.

Transcription

1 Atmosphere Atmosphere- a thin layer of air that forms a protective covering around the planet. If Earth had no atmosphere, days would be extremely hot and nights would be extremely cold. Earth's atmosphere is a mixture of gases, solids, and liquids that surround the planet. More than 2 billion years ago, Earth's early organisms released oxygen into the atmosphere. Before then, the atmosphere was mostly made up of nitrogen and carbon dioxide.

2 Gases in the Atmosphere Today's atmosphere is a mixture of the gases shown below. Nitrogen is the most abundant gas, making up 78% of the atmosphere. Oxygen actually makes up only 21 % of Earth's atmosphere. As much as 4 % of the atmosphere is water vapor. Other gases that make up Earth's atmosphere include argon and carbon dioxide. The composition of the atmosphere is changing in small but important ways. For example, car exhaust emits gases into the air.

3 Solids and Liquids in Earth's Atmosphere In addition to gases, Earth's atmosphere contains small, solid particles such as dust, salt, and pollen. Dust particles get into the atmosphere when wind picks them up off the ground and carries them along. Salt is picked up from ocean spray. Plants give off pollen that becomes mixed throughout part of the atmosphere. On June 12, 1991, Mount Pinatubo in the Philippines erupted, causing liquid droplets to form in Earth's atmosphere.

4 Layers of the Atmosphere There are five layers of the atmosphere, each with its own properties.

5 Lower Layers of Atmosphere Troposphere~ This is where we study, eat, sleep, and play. This is the lowest of Earth's atmospheric layers. *contains 99% of the water vapor and 75% of the atmospheric gases *rain, snow, and clouds occur in this layer *extends up to about 10 km Stratosphere~ This is the layer directly above the troposphere *extends from 10 km to 50 km above Earth's surface *contains a higher level of ozone

6 Upper Layers of Atmosphere Mesosphere~ This is the layer directly above the stratosphere. *extends from top of stratosphere to about 85 km above Earth's surface *Shooting stars can be seen in the mesosphere Thermosphere~ This is named for its high temperatures. *This is the thickest atmospheric layer *found between 85 km and 500 km above Earth's surface Ionosphere~ Within the mesosphere and the thermospere is a layer of electrically charged particles *am radio waves can travel through the ionosphere and travel much further at night than during the day. Exosphere~ This is where you would find a space shuttle. *so few molecules that wings of a shuttle are useless here *beyond exosphere is outer space

7 Atmospheric Pressure Like molecules anywhere else, atmospheric gases have mass. Atmospheric gases extend hundreds of kilometers above Earth's surface. As Earth's gravity pulls the gases towards its surface, the weight of these gases presses down on the air below. These molecules are closer together and therefore, exert more pressure. This is known as atmospheric pressure. *air pressure is greater near Earth's surface *decreases as you go higher up into atmosphere *harder to breathe in mountainous areas because there are fewer molecules. *planes must maintain pressurized cabins so that people can breathe.

8 Temperature in Atmospheric Layers The sun is the source of most of the energy on Earth. Before it reaches Earth, the sun's energy must pass through the atmosphere. *some gases easily absorb the sun's energy *some gases do not~ this is why the different layers of the atmosphere have different temperatures. *ozone molecules absorb the sun's energy and raise the temperature in the stratosphere.

9 The Ozone Layer Ozone is made of oxygen. Although you can't see it, your life depends on it! *found about 19 km above your head *ozone has 3 atoms of oxygen bound together *shields us from the sun's harmful energy *absorbs most of the ultraviolet radiation that enters the atmosphere.

10 CFC's and Ozone Holes Chlorofluorocarbons (CFC's)~ These are air pollutants that are destroying the ozone layer. *CFC's destroy ozone *chemical compounds found in some refrigerators, air conditioners, and aerosol sprays *Each year more than 1.3 million Americans develop skin cancer and more than 9,500 die from it *Scientists found one large hole over Antartica and a smaller hole was discovered over the North Pole.