Presentation on theme: "Chapter 6 The Atmosphere 6 th Grade. Section 1 The atmosphere is a mixture of gases that surrounds the earth. It contains the oxygen you breathe and protects."— Presentation transcript:
Section 1 The atmosphere is a mixture of gases that surrounds the earth. It contains the oxygen you breathe and protects us from radiation from the sun. Every breath, tree planted, time you start the car affects the atmosphere.
Atmosphere The atmosphere is made up of mostly nitrogen—78%. Oxygen makes up 21% of the atmosphere. 1% is Argon, Carbon Dioxide, water vapor, and various other gasses. The atmosphere also contains dust, volcanic ash, sea salt, dirt, and smoke. Water is also present in the atmosphere. We breathe out water.
Atmosphere Air pressure adds up. At sea level a square inch surface is under almost 15 lbs of air. This is the same as carrying a bowling ball on the tip of your finger. As the altitude increases the air pressure decreases. The atmosphere is held around the earth by gravity. Air pressure is the measure of the force with which air molecules push on the surface. It is strongest at the surface. WHY???
Atmosphere Air temperature also changes as altitude increases. This is because where gases are located. Different types of gases absorb heat differently. This is why some parts are warmer where others are cooler.
Atmosphere The atmosphere is divided into four layers. Troposphere: where gases turn and mix. Stratosphere: layered, not much mixing. Mesosphere: means middle. Thermosphere: Thermo means heat….where temperatures are the highest.
Atmosphere Troposphere: layer in which we live. It is next to the earth’s surface. It is the densest atmospheric layer. Contains 90% of the atmosphere’s total mass. Almost all of earth’s carbon dioxide, water vapor, clouds, air pollution, weather, and life forms are in the troposphere. Temperatures vary greatly because of the gases mixing in the troposphere.
Atmosphere Stratosphere: home of the ozone layer Gases in this area are layered and do not mix as much as they do in the troposphere. The air is very thin in this layer and it contains very little moisture. Lower stratosphere is very cold -60 C. Temperatures rise as altitude increases. This rise occurs because ozone in the stratosphere absorbs ultraviolet radiation from the sun—this warms the air. The ozone protects life on earth by absorbing the harmful ultraviolet radiation.
Atmosphere Mesosphere: the area above the stratosphere. It is the middle layer of the atmosphere. It is the coldest layer. Temperatures can be as low as -93C at the top of the mesosphere. Thermosphere: uppermost atmospheric layer. Temperature increases with altitude. Atoms of nitrogen and oxygen absorb high- energy solar radiation and release thermal energy. The temperatures can be 1000C or higher. However, it does not feel hot. Temperature is different from heat. Temperature—average energy of particles in motion. The particles are moving really fast. Heat is the transfer of energy from particle to particle. So much space in the thermosphere the particles do not touch so not much energy is transferred.
Atmosphere Ionosphere: upper mesosphere and lower thermosphere. Nitrogen and oxygen absorb harmful solar energy. This causes the temperatures to rise and gas particles become electrically charged. The electrically charged particles are called ions. This is why it is called ionosphere. Some areas radiate energy as shimmering lights called auroras. This is also the area where radio waves reflect off of and can travel around the world.
Section 2 Radiation: The earth receives energy from the sun by radiation. Radiation is the transfer of energy as electromagnetic waves. The earth only receives about two-billionths of the energy the sun radiates. This small fraction is enough to drive the weather cycle and make earth habitable. Conduction: when you touch something hot you have experienced it. Thermal conduction is the transfer of thermal energy through a material. It is always transferred from warmer to cooler areas.
Atmospheric Heating 50% of the energy from the sun is absorbed by the earth’s surface. 20% absorbed by the clouds, ozone, and atmospheric gases. 25% is scattered and reflected by clouds and air. 5% is reflected by the earth’s surface.
Atmospheric Heating Convection: Energy transfer by circulation. Ex. watching a pot of water boil. This is the transfer of thermal energy by the circulation or movement of a liquid or gas. Cool air sinks and warm air rises. The cool air is warmed and the process is repeated. Hotter air is less dense so it rises. This is called convection current. Pg. 157.
Atmospheric Heating Greenhouse effect: 70% of radiation that enters earth’s atmosphere is absorbed by clouds and the earth’s surface. The energy is converted into thermal energy that warms the planet. Most of this should escape back into space. The atmosphere traps it and keeps it within the earth. This is called the greenhouse effect. Greenhouse effect: the warming of the surface and lower atmosphere of earth that occurs when water vapor, carbon dioxide, and other gases absorbed and reradiate thermal energy. It is kind of like the glass walls and roof of a greenhouse---which prevent solar energy from escaping.
Atmospheric Heating For earth to remain livable the amount of energy received from the sun and returned to space must be approximately equal. This balance is known as the radiation balance. Many scientist are concerned that temperatures are rising. This global temperature rise is called global warming. The burning of fossil fuels and deforestation are increasing greenhouse gases—CO 2. This rise in temperature could interrupt climate patterns. Plants and animals that are adapted to live in specific temperatures could be affected. However, this debate over this actually occurring is ongoing. Climate models are extremely complex.
Section 3 Wind: the movement of air caused by differences in air pressure. The greater the pressure difference and the closer the pressure systems are to each other the faster the wind moves. Air pressure differences are caused by unequal heating of the earth. Equator: warmer so air rises and creates a less dense area with lower pressure. Moves towards the poles and lowers. It is denser so cold air sinks. As the cold air sinks it creates high pressure.
Air Air travels in a large circular pattern. This is called convection cells. It looks like cells. These are separated by pressure belts. This is bands of high and low pressure found about every 30 degrees latitude. As warm air rises and moves toward the poles at about 30 degrees from the equator---30 degrees North and South it sinks or rises depending on the direction it is traveling. Pg. 161. Warm air rising creates low pressure belt. Cold air sinking creates high pressure belt.
The Coriolis Effect Winds do not travel directly from north or south because the Earth is rotating. Coriolis Effect: the apparent curving of the path of a moving object from an otherwise straight path due to the Earth’s rotation. Northern hemisphere: winds traveling north curve to the east and winds traveling south curve to the west. http://www.mhhe.com/biosci/genbio/tlw3/eBridge/Ch p29/animations/ch29/global_wind_circulation.swf http://www.mhhe.com/biosci/genbio/tlw3/eBridge/Ch p29/animations/ch29/global_wind_circulation.swf
Global Winds Air cells and the Coriolis effect produce patterns of air circulation called global winds. Three major global winds. Polar Easterlies: wind belts that extend from the poles to 60 degrees latitude in both hemispheres. Formed as cold, sinking air moves from the poles to 60 degrees north and 60 degrees south latitude. This is what carries cold arctic air over the U.S. Blows from the East. Westerlies: wind belts from 30 degrees to 60 degrees latitude in both hemispheres. Carries moist air over the U.S. to produce rain and snow.
Global Winds Trade Winds: in both hemispheres. Blows from 30 degrees latitude and almost to the equator. The Coriolis effect causes trade winds to curve to the west in the Northern Hemisphere and to the East in the Southern Hemisphere. Early sailors used trade winds to sail from Europe to America.
Trade Winds The Doldrums: Trade winds of the Northern and Southern Hemispheres meet in an area around the equator. In the doldrums there is very little wind because of warm, rising air creates a low pressure area. The Horse Latitudes: 30 degrees north and 30 degrees south latitude, sinking air creates an area of high pressure. Winds are weak. Most of the worlds deserts are found in horse latitudes.
Winds Jet Streams: narrow belts of high speed winds that blow in the upper troposphere and lower stratosphere. They can blow as fast as 400 km/h. They do not follow regular paths around the earth like global winds. Jet streams affect the movement of storms. Also helps pilots. Flying from west to east can be faster than flying east to west. Local winds move short distances and can blow from any direction. This is caused by temperature differences caused by mountains and water. Pg. 164 Mountain and valley breezes. Warm air rises during the day and moves up mountain slopes. As the air cools it moves down the mountain and into the valleys.
Section 4 Air pollution: the contamination of the atmosphere by the introduction of pollutants from human and natural sources. Primary pollutants: pollutants put directly into the air by human or natural activities. Ex. dust, volcanic gases, ash, smoke, pollen, CO, various chemicals. Secondary pollutants: when primary pollutants react with other primary pollutants or naturally occurring substances. Ozone and Smog are examples. Smog=when ozone and vehicle exhaust react with sunlight.
Human caused air pollution Cars-10-20% of human caused air pollution in the U.S. causes smog and acid rain. Industrial air pollution: burns fossil fuels to produce energy. Oil refineries, chemical manufacturing plants, dry cleaning businesses, furniture refinishers are potential sources of air pollution. Indoor air pollution: pg. 168.
Air Pollution Acid precipitation: rain, sleet, or snow that contains high amounts of acids. Caused by the burning of fossil fuels. This burning releases sulfur dioxide and nitrogen oxide. When they combine with water they form sulfuric acid and nitric acid. Acid precipitation can cause the level of acid in the soil to increase. This is called acidification. When the acid level is increased some nutrients the plants need are dissolved. The acid can also release some toxic metals to be released and are absorbed by the roots of the plant.
Acid Precipitation Acid precipitation can damage an entire forest. This can destroy the entire ecology of the forest. If acid is increased in aquatic areas everything in the water may die. Tends to be the worst in the spring because of melting acid snow. Increases the acid in the water quickly---this is called acid shock. Some communities spray lime on acidified lakes which balances the pH.
Ozone Ozone hole: Thinning of the ozone over the Antarctic. This is caused by CFCs. Less ozone means that more UV light rays penetrate. UV radiation damages genes and causes skin cancer. Banned CFCs but they can remain in the stratosphere for 60-120 years. So they are still destroying the atmosphere. Chlorofluorocarbon
Air Pollution and Human Health Pg. 171---read aloud. Cleaning air pollution: Clean Air Act was passed by congress in 1970. It gives the EPA the authority to control the amount of air pollutants that can be released from any source---like cars or factories. They also check air quality. Scrubber: a device that is used to remove pollutants before they are released by smokestacks. Ex. used in coal burning power plants.