Earth’s AtmosphereEarth’s Atmosphere

The The three main featuresthree main features of the of the Earth are the Earth are the landland, the , the waterwater and theand the airair. .

Land areas include the seven Land areas include the seven continents and other landmasses. continents and other landmasses. Scientists call all the land on Earth Scientists call all the land on Earth the the lithospherelithosphere – “rock sphere”. – “rock sphere”.

• The water on Earth makes up the The water on Earth makes up the hydrospherehydrosphere ( (hydrohydro means water). About means water). About 97% of Earth’s water is salt water leaving 97% of Earth’s water is salt water leaving only 3% fresh water. Of the 3% of Fresh only 3% fresh water. Of the 3% of Fresh water nearly 85% is trapped in ice. water nearly 85% is trapped in ice.

• The oxygen that you breathe is found in The oxygen that you breathe is found in the last great sphere that makes up planet the last great sphere that makes up planet Earth, the Earth, the atmosphere.atmosphere. The atmosphere The atmosphere is the envelope of gases that surrounds is the envelope of gases that surrounds the Earth. the Earth.

• About 3.8 billion years ago, chemical About 3.8 billion years ago, chemical reactions triggered by sunlight produced reactions triggered by sunlight produced new substances in the atmosphere. new substances in the atmosphere.

• The The ozone layerozone layer is sometimes referred to as is sometimes referred to as an “umbrella” for life on Earth. The ozone an “umbrella” for life on Earth. The ozone layer absorbs much of the harmful radiation layer absorbs much of the harmful radiation from the sun. The ozone is made up of atoms from the sun. The ozone is made up of atoms of oxygen. of oxygen.

• Today, the atmospheric gases include Today, the atmospheric gases include nitrogen nitrogen – 78%, – 78%, oxygen oxygen – 21%, less than 1% – 21%, less than 1% of [carbon dioxide, water vapor, argon, and of [carbon dioxide, water vapor, argon, and trace gases (neon, helium, krypton, and trace gases (neon, helium, krypton, and xenon)]. xenon)].

• Gravity is a force of attraction by which Gravity is a force of attraction by which objects are pulled toward each other. Because objects are pulled toward each other. Because of gravity, the layers of air surrounding the of gravity, the layers of air surrounding the Earth push down on the Earth’s surface. This Earth push down on the Earth’s surface. This push is called push is called air pressure.air pressure.

• The four main layers of the The four main layers of the atmosphere are the troposphere, atmosphere are the troposphere, stratosphere, mesosphere, and the stratosphere, mesosphere, and the thermosphere. thermosphere.

• Almost all of Almost all of the Earth’s weather the Earth’s weather occurs in the troposphereoccurs in the troposphere..

• The The ozone layerozone layer is sometimes referred to as is sometimes referred to as an “umbrella” for life on Earth. The ozone an “umbrella” for life on Earth. The ozone layer absorbs much of the harmful radiation layer absorbs much of the harmful radiation from the sun. The ozone is made up of atoms from the sun. The ozone is made up of atoms of oxygen. of oxygen.

• Today, the atmospheric gases include Today, the atmospheric gases include nitrogen nitrogen – 78%, – 78%, oxygen oxygen – 21%, less than 1% – 21%, less than 1% of [carbon dioxide, water vapor, argon, and of [carbon dioxide, water vapor, argon, and trace gases (neon, helium, krypton, and trace gases (neon, helium, krypton, and xenon)]. xenon)].

• Gravity is a force of attraction by which Gravity is a force of attraction by which objects are pulled toward each other. Because objects are pulled toward each other. Because of gravity, the layers of air surrounding the of gravity, the layers of air surrounding the Earth push down on the Earth’s surface. This Earth push down on the Earth’s surface. This push is called push is called air pressure.air pressure.

• The four main layers of the The four main layers of the atmosphere are the troposphere, atmosphere are the troposphere, stratosphere, mesosphere, and the stratosphere, mesosphere, and the thermosphere. thermosphere.

• Almost all of Almost all of the Earth’s weather the Earth’s weather occurs in the troposphereoccurs in the troposphere..

• Temperature decreases with Temperature decreases with increasing altitude because the air increasing altitude because the air becomes less dense. The temperature becomes less dense. The temperature of the troposphere drops about 6.5of the troposphere drops about 6.5oo C C for every kilometer above the Earth’s for every kilometer above the Earth’s surface. However, at an altitude of surface. However, at an altitude of about 12 kilometers, the temperature about 12 kilometers, the temperature seems to stop dropping. The zone of seems to stop dropping. The zone of the troposphere where the the troposphere where the temperature remains fairly constant is temperature remains fairly constant is called the called the tropopause.tropopause. The The tropopause divides the troposphere tropopause divides the troposphere from the next layer of the atmosphere.from the next layer of the atmosphere.

• Most of the ozone in the atmosphere Most of the ozone in the atmosphere is located in a layer of the is located in a layer of the stratosphere. stratosphere.

• The upper mesosphere is the coldest The upper mesosphere is the coldest region of the atmosphere. region of the atmosphere.

• The thermosphere is made up of the The thermosphere is made up of the ionosphere and the exosphere. ionosphere and the exosphere.

• The Van Allen radiation belts are layers The Van Allen radiation belts are layers of high radiation that form as a result of high radiation that form as a result of the concentration of charged of the concentration of charged particles.particles. These charged particles are These charged particles are from storms which occur on the sun.from storms which occur on the sun.

• When there is a solar flare, the When there is a solar flare, the magnetosphere is bombarded by large magnetosphere is bombarded by large quantities of electrically charged quantities of electrically charged particles from the sun. These charged particles from the sun. These charged particles get trapped in the particles get trapped in the magnetosphere. Here they collide with magnetosphere. Here they collide with other particles in the upper other particles in the upper atmosphere. The collisions cause the atmosphere. The collisions cause the atmospheric particles to give off light. atmospheric particles to give off light. The multicolored lights are called The multicolored lights are called auroras.auroras.