Atmosphere 15.1 – Earth’s Atmosphere

What is Atmosphere? A thin layer of air that protects the Earth’s surface from extreme temperatures and harmful Sun rays.

What is the Atmosphere made of? A mixture of gases, solids, and liquids Earth’s early atmosphere was much different than today. Volcanoes produced nitrogen and carbon dioxide, but little oxygen. More than 2 billion years ago simple organisms (cyanobacteria) began producing oxygen. Eventually oxygen formed an ozone layer that protected Earth from harmful ultraviolet rays from the Sun. Green plants and diverse life forms developed due to the ozone layer and the protection it gave from the harsh Sun rays.

Atmospheric Make-up Continued Atmospheric gases include: Nitrogen – 78% Oxygen – 21% Carbon Dioxide - .03% Water Vapor – 0-4% Argon – 0.93% The atmosphere is changing with the introduction of pollutants: increasing human energy use is increasing the amount of Carbon Dioxide. Pollutants mix with oxygen and other chemicals to form smog.

Atmospheric Make-up Continued The solids that make up the atmosphere include: Dust Salt Pollen The liquids that make up the atmosphere include: Water droplets Droplets from volcanoes

Layers of the Atmosphere 5 main layers of the atmosphere: Low Layers Troposphere – Lowest layer, where we live. Extends about 10 km up and contains most of the water vapor and gases. Stratosphere – Extends from 10 km to 50 km and contains the ozone layer. Upper Layers Mesosphere – Extends from 50-85 km and is where meteors are visible. Ionosphere – Between the meso- and thermosphere. Has charged particles that can help carry radio waves. Thermosphere – Extends from 85-500 km and is the thickest layer. Has high temperatures. Exosphere – Outer layers where the space shuttle flies and has very few molecules.

Atmospheric Pressure Molecules closer to the surface are more densely packed (at higher pressure) than those higher in the atmosphere because of the mass of gases pressing down from higher in the atmosphere.

Temperature in the Layers The troposphere is warmed primarily by the Earth’s surface; temperature decreases as altitude increases in this layer. Temperature increase as altitude increases in the stratosphere, particularly the upper portion because ozone absorbs energy from the Sun. Temperatures decrease with altitude in the mesosphere. Thermosphere and exosphere are the first to receive the Sun’s rays, so they are very warm.

A closer look at the Ozone Layer About 19-48 km above Earth in the stratosphere, this layer of 3-atom oxygen molecules (O3) protects the Earth from the Sun’s harmful ultraviolet radiation. Life on Earth depends on it. Pollutants called chlorofluorocarbons (CFCs) are destroying the ozone layer. CFCs are using in refrigerators, air conditioners, aerosol sprays, and foam packaging. If these products develop a leak, CFCs can enter the atmosphere. The ozone layer has a large hole over Antarctica 10.6 million square miles wide.

The End… any questions?