Earth’s atmosphere Chapter 1 Section 1

Importance of the Atmosphere The Earth’s atmosphere is a thin layer that forms a protective covering around the planet. If there was no atmosphere, days would be extremely hot and nights would be extremely cold. It also protects from the Sun’s harmful rays.

Makeup of the Atmosphere The atmosphere is a mixture of solids, liquids, and gases that surrounds the planet. The atmosphere extends from the Earth’s surface all the way to outer space. Earth’s early atmosphere contained mostly nitrogen and carbon dioxide Eventually, a layer that was rich in ozone was formed in the upper atmosphere, and protected Earth from the Sun’s harmful rays and allowed plants to flourish all over the Earth. These plants released tons of oxygen into the atmosphere and made the atmosphere like what it is today.

Gasses in the Atmosphere Today’s atmosphere is a mixture of gases: Nitrogen – 78% Oxygen – 21% Argon – 0.93% Carbon dioxide – 0.03% Several trace elements

Gasses in the Atmosphere (cont.) The makeup of the atmosphere is always changing. Car exhaust emits gasses into the atmosphere and pollutants like this can mix with other chemicals and sunlight. When they mix they form a brown haze called smog. Humans burn fuel for energy and as the fuel is burned carbon dioxide enters the atmosphere. If we increase the amount of energy used we will increase the amount of carbon dioxide in the atmosphere.

Solids and Liquids in the Earth’s Atmosphere The atmosphere contains small, solid particles such as dust, salt, and pollen. Dust gets picked up from the Earth’s surface from the wind. Salt gets picked up from ocean spray. Pollen is released into the atmosphere by plants. The atmosphere also contains small, liquid droplets other than water droplets in the clouds. The atmosphere constantly moves these solid and liquid particles from one region to another.

Layers of the Atmosphere There are 5 layers of the Earth’s atmosphere. The lower atmospheric layers: Troposphere Stratosphere The upper atmospheric layers: Mesosphere Thermosphere Exosphere

Lower Layers of the Atmosphere The troposphere is the lowest layer of the atmosphere Extends from the Earth’s surface to about 10 km into the atmosphere. Contains 99% of the water vapor in the atmosphere Contains 75% of all the gasses in the atmosphere The layer we live in The stratosphere is the layer directly above the troposphere that Extends from 10 km to 50 km above the Earth’s surface. Contains the highest concentration of ozone gas

Upper Layers of The Atmosphere The mesosphere is the middle layer of the atmosphere. Extends from the stratosphere to about 85 km Contains part of the ionosphere The thermosphere is named for its high temperatures. Extends from the mesosphere to about 500 km Contains part of the ionosphere The exosphere is the furthest layer of the atmosphere. Its where satellites can be found Contains very few particles

Atmospheric Pressure Atmospheric gasses extend hundreds of km above the Earth’s surface. As the Earth’s gravity pulls the gasses down on the Earth’s surface, the weight of these gasses presses down on the air below. This causes the molecules closest to the Earth’s surface to be closer to each other. Which makes the air closest to the Earth’s surface to be more dense than air further away.

Atmospheric Pressure (cont) The dense air closer to the Earth’s surface exerts more force than the less dense air near the top of the atmosphere. Force exerted on an area is known as pressure. Air pressure is greater near the Earth’s surface and deceases higher in the atmosphere. People find it harder to breathe in high mountains because fewer molecules of air exist there. Jets that fly above the troposphere must maintain pressurized cabins so that people can breathe.

Temperature in Atmospheric Layers The Sun is the source of most of the energy on Earth. Because some layers contain gasses that easily absorb the Sun’s energy while other layers do not, different layers have different temperatures

Temperature in Atmospheric Layers (cont) Molecules of ozone in the stratosphere absorb some of the Sun’s energy. Energy absorbed by ozone molecules raises the temperature. There are more ozone molecule in the upper portion of the stratosphere, the temperature raises with increasing altitude. Temperature in the thermosphere and exosphere are high because there are few molecules, however each molecule has a great deal of energy.

The Ozone Layer The ozone layer is a atmospheric layer that is about 19 km to 48 km above the Earth’s surface. The ozone layer consists of ozone molecules. Ozone = 3 oxygen molecules The ozone layer contains a high concentration of ozone and shields you from the Sun’s harmful energy. Ozone absorbs most of the ultraviolet radiation that enters the atmosphere. Ultraviolet radiation is one of the many types of energy that come to Earth from the sun. Too much exposure to ultraviolet radiation can damage your skin and cause cancer.

Chlorofluorocarbons (CFCs) Air pollutants, like chlorofluorocarbons, are destroying the atmosphere. Chlorofluorocarbons (CFCs) are chemical compounds used in some refrigerators, air conditioners, and aerosol sprays, and in the production of some foam packaging. CFCs can enter the atmosphere if these appliances leak or of they and other products containing CFCs are improperly discarded.

The Ozone Hole The destruction of ozone molecules by CFCs seems to cause seasonal reduction in ozone over Antarctica called the ozone hole. Beginning in late August or early September the amount of ozone in the atmosphere over Antarctica begins to decrease. By October, the ozone concentration reaches its lowest values and then begins to increase again. By December, the ozone hole disappears.

The Ozone Hole (cont) In the mid-1990s, many governments banned the production and use of CFCs. Since then, the concentration of CFCs in the atmosphere has started to decrease.