Atmosphere15.1 – 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 ContinuedAtmospheric 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 ContinuedThe solids that make up the atmosphere

include:DustSaltPollen

The liquids that make up the atmosphere include:Water dropletsDroplets from volcanoes

Layers of the Atmosphere5 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 PressureMolecules 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 LayersThe 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 LayerAbout 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?