Chapter 1 Vocabulary Atmosphere Altitude Density Cycle Radiation Conduction Convection Ultraviolet Radiation Infrared Radiation Ozone Greenhouse Effect Greenhouse Gas Air pollution Particulate Fossil fuel Smog

Earth’s Changing Atmosphere 7 th Grade Science Mrs. Redwine

Earth's Atmosphere The atmosphere is a thin layer of air that surrounds the Earth and protects its surface from extreme temperatures and harmful sun rays. The atmosphere is a thin layer of air that surrounds the Earth and protects its surface from extreme temperatures and harmful sun rays. Figure 1.1 Thin Gaseous envelope

The Atmosphere Makes Life on Earth Possible The gases of the atmosphere keep Earth warm and transports energy to different regions of the planet. Without the atmosphere: Oceans would not exist Life would not survive The planet would be a cold, lifeless rock.

Characteristics of the Atmosphere Altitude The distance above sea level The higher you go, the higher the altitude Air becomes thinner as the altitude increases

Characteristics of the Atmosphere Density The amount of mass in a given volume of a substance If two objects take up the same amount of space, the object with more mass has a greater density The thickness or thinness of air is measured by its density The atmospheres density decreases as you travel upward

Materials in the Atmosphere The atmosphere contains tiny particles of solid or liquid material such as dust, sea salt, and water droplets Gases in the atmosphere Nitrogen makes up 78% Promotes plant growth Oxygen makes up 21% Necessary for animals and plants to perform life processes Argon, Carbon Dioxide, and other gases make up 1% Plants use carbon dioxide to make food and water Water Vapor varies from place to place ranging from 0 to 4% Used for clouds and precipitation

Natural Processes that modify the Atmosphere The Carbon Cycle Carbon dioxide(CO2) and oxygen (O2) gases constantly circulate, or cycle, among plants, animals, and the atmosphere. Ex: Animals inhale air, use some of its oxygen, and exhale air that has less oxygen but more carbon dioxide and water. Ex: Plants take in carbon dioxide and release oxygen as they make food in the process of photosynthesis

Natural Processes that modify the Atmosphere The Nitrogen Cycle Different forms of nitrogen cycle among the atmosphere, the soil, and living organisms. Tiny organisms remove nitrogen gas (N2) from the air and transform it into other chemicals, which then enter the soil. Plants and animals use solids and liquids that contain nitrogen, which returns to the soil when the organisms die and decay. The soil slowly releases nitrogen back into the air as nitrogen gas.

Natural Processes that modify the Atmosphere The Water Cycle Different forms of water (H20) cycle between Earth’s surface and the atmosphere. Ex: Liquid water from oceans and lakes changes into gas and enters the atmosphere Ex: Plants release water vapor from their leaves Ex: Liquid water falls from the atmosphere as rain

Natural Processes that modify the Atmosphere In addition to ongoing processes, dramatic events may cause changes in the atmosphere. When sudden events occur, it takes time before the atmosphere is able to restore balance. Volcanic Eruptions Volcanoes shoot gases and huge amounts of ash into the atmosphere. Certain gases produce a haze that may affect the air for many months and lower temperatures worldwide Forest Fires When forest burn, the carbon that make sup each tree combines with oxygen and enters the atmosphere as carbon dioxide. Wood ash also enters the atmosphere. Dust Storms Wind, water, or drought can loosen soil. Powerful windstorms may then raise clouds of this eroded soil. These storms add huge amounts of particles to the air for a time.