THE ATMOSPHERE Learning Goal: Describe how the composition and structure of the atmosphere protects life on Earth. Essential Question: How does the composition and structure of the atmosphere protects life on Earth.

Main Ideas: The atmosphere is divided into laters. The atmosphere protects life from harmful radiation and regulates the planet’s temperature. Weather is caused by changes in the atmosphere due to the transfer of energy in one form or another. This energy transfer is driven by the solar radiation from the sun.

The Atmosphere Atmosphere: the blanket of gasses that surrounds our planet held by gravity

The Early Atmosphere Thought to be mostly water vapor and carbon dioxide. Water vapor condensed and rained to fill the oceans. The first organisms used carbon dioxide to perform photosynthesis which made oxygen.

Today’s Atmospheric Composition 78% Nitrogen (N) 21% Oxygen (O2) 1% Other Gasses

The atmosphere also contains: water vapor: which forms clouds and precipitation and absorbs heat energy particles: like dust, salt, pollen ozone: a gas in the ozone layer that absorbs harmful UV radiation. Greenhouse gasses: gas molecules that absorb solar radiation, trap heat, and can increase the temperature of the atmosphere. Carbon dioxide: most worrisome Water vapor: most abundant

Atmospheric Layers There are 5 layers of the atmosphere, divided by temperature. Temperature is a measure of the average amount of kinetic energy of the particles in a material. (motion)

Layers from top to bottom: Exosphere Thermosphere Mesosphere Stratosphere Troposphere

Exosphere (“Exo”- means outer) outermost layer with no clear boundary It extends into space

Thermosphere (“therm-” means heat) Very little air here Known for its great range of temperatures (-112⁰ F - 2000 ⁰ F) Layer where space shuttles orbit Produces the Aurora Borealis (Northern Lights)

Temperature decreases. Where meteors burn up and make shooting stars. Mesosphere (“Meso-” means middle) Air is very thin Temperature decreases. Where meteors burn up and make shooting stars.

Stratosphere Air is pretty thin contains the “Ozone Layer” which is made of ozone gas that protects us from harmful UV radiation by absorbing it This is why temperature in the stratosphere increases.

Troposphere Bottom layer that contains most of the air. Temperature decreases with altitude because the Earth’s surface warms it. Where all weather occurs

Where all weather occurs. The Sun heats the Earth through radiation. The clouds block the sun during the day and keep heat in at night. Water vapor and carbon dioxide also absorb heat and help keep it warm at night.

The ground absorbs the Sun’s radiation. The ground heats the air above it through conduction. It gets cooler the farther away you get from the ground.

Convection TRIES to evenly distribute heat in the troposphere. Warm, moist air rises, and cool air sinks and rushes in to replace it. This creates wind. It is also how clouds form.

All three types of energy transfer happen in the troposphere.

Altitude is the height above sea level. The higher you go, the less air there is.

Pressure is the weight of the air above you The higher you go, the less air there is, so pressure decreases with altitude.