Earth’s AtmosphereEarth’s Atmosphere

AtmosphereAtmosphere The atmosphere is a The atmosphere is a

thin layer of gases thin layer of gases that surround the that surround the Earth.Earth.

The atmosphere The atmosphere protects the Earth by protects the Earth by balancing the balancing the amount of heat amount of heat absorbed from the absorbed from the Sun and the amount Sun and the amount of heat that escapes of heat that escapes back into space. back into space.

The Past AtmosphereThe Past AtmosphereIt is theorized that 4 billion years ago the It is theorized that 4 billion years ago the

Earth’s atmosphere contained two deadly Earth’s atmosphere contained two deadly gases: methane and ammonia.gases: methane and ammonia.

How did the atmosphere How did the atmosphere change?change?

Methane is made up carbon and hydrogen.Methane is made up carbon and hydrogen. Ammonia, is composed of nitrogen and Ammonia, is composed of nitrogen and

hydrogen.hydrogen. Sunlight caused chemical reaction among Sunlight caused chemical reaction among

the methane, ammonia and water in the air.the methane, ammonia and water in the air. New materials, nitrogen, hydrogen and New materials, nitrogen, hydrogen and

carbon dioxide, were formed as the carbon dioxide, were formed as the methane and ammonia broke down.methane and ammonia broke down.

Ancient AtmosphereAncient Atmosphere

The water vapor remained.The water vapor remained. Hydrogen, a lightweight gas, escaped into Hydrogen, a lightweight gas, escaped into

space. space. Nitrogen, carbon dioxide and water vapor Nitrogen, carbon dioxide and water vapor

were left.were left. Sunlight then broke down the water vapor in Sunlight then broke down the water vapor in

the upper atmosphere into hydrogen and the upper atmosphere into hydrogen and oxygen. The hydrogen again escaped.oxygen. The hydrogen again escaped.

Ozone LayerOzone Layer The oxygen that was left The oxygen that was left

behind joined together, in behind joined together, in sets of three, to form a gas sets of three, to form a gas known as ozone.known as ozone.

A layer of ozone gas formed A layer of ozone gas formed about 30 km above the about 30 km above the Earth’s surface.Earth’s surface.

The ozone layer absorbs The ozone layer absorbs harmful ultraviolet radiation harmful ultraviolet radiation from space.from space.

OceansOceans Before the ozone layer formed, the only Before the ozone layer formed, the only

living things on Earth were microscopic living things on Earth were microscopic organisms that lived far below the surface of organisms that lived far below the surface of the oceans.the oceans.

After the ozone layer After the ozone layer formed, certain types formed, certain types of these of these microorganisms called microorganisms called blue-green bacteria blue-green bacteria started to appear on started to appear on or near the water’s or near the water’s surface.surface.

Blue-green BacteriaBlue-green Bacteria

These bacteria used the These bacteria used the energy in sunlight to combine energy in sunlight to combine carbon dioxide from the air carbon dioxide from the air with water to produce food.with water to produce food.

A byproduct of this food-A byproduct of this food-making process was oxygen. making process was oxygen. This was the first “free This was the first “free oxygen”.oxygen”.

OxygenOxygen Unlike ozone, oxygen remains near the Unlike ozone, oxygen remains near the

surface of the Earth.surface of the Earth. This is the oxygen that animals breathe This is the oxygen that animals breathe

today.today. Green plants began to grow on land and Green plants began to grow on land and

take in carbon dioxide and release oxygen take in carbon dioxide and release oxygen in the food-making process.in the food-making process.

Today’s AtmosphereToday’s Atmosphere 600 million years ago the amounts of 600 million years ago the amounts of

oxygen and carbon dioxide in the oxygen and carbon dioxide in the atmosphere began to level off.atmosphere began to level off.

Since that time, the composition of the Since that time, the composition of the atmosphere has remained fairly constant.atmosphere has remained fairly constant.

Composition of the AtmosphereComposition of the Atmosphere Nitrogen gas makes up about 78 percent Nitrogen gas makes up about 78 percent

of the atmosphere.of the atmosphere. Oxygen accounts for 21 percent.Oxygen accounts for 21 percent.• The remaining 1

percent is a combination of carbon dioxide, water vapor, argon and trace gases.

Solid ParticlesSolid Particles

Tiny particles of dust, smoke dirt and salt Tiny particles of dust, smoke dirt and salt float in the air.float in the air.

Every time a wave breaks, tiny particles of Every time a wave breaks, tiny particles of salt from ocean water are suspended.salt from ocean water are suspended.

Dust in the air comes from the eruption of Dust in the air comes from the eruption of volcanoes.volcanoes.

Dirt and smoke comes from people as they Dirt and smoke comes from people as they burn fuels and drive cars.burn fuels and drive cars.

Layers of the AtmosphereLayers of the Atmosphere

The atmosphere is The atmosphere is divided into layers divided into layers according to the according to the major changes in its major changes in its temperature. Layers temperature. Layers with thinner particles with thinner particles can hold less heat.can hold less heat.

Air PressureAir Pressure The layers of air that surround The layers of air that surround

the Earth are held close to it the Earth are held close to it by the force of gravity.by the force of gravity.

Because of gravity, the layers Because of gravity, the layers of air push down on the of air push down on the Earth’s surface. This is called Earth’s surface. This is called air pressure.air pressure.

The upper layers push down The upper layers push down on the lower layers so the air on the lower layers so the air pressure near the surface is pressure near the surface is greater than the air pressure greater than the air pressure further away.further away.

The TroposphereThe Troposphere This is the layer closest to the Earth.This is the layer closest to the Earth. Weather occurs in this layer. Life occurs in the Weather occurs in this layer. Life occurs in the

troposphere.troposphere.

The height of the The height of the troposphere varies troposphere varies from the Equator to from the Equator to the poles. (17-8 km)the poles. (17-8 km)

It is highest at the It is highest at the equator.equator.

This layer contains This layer contains 99% of the water 99% of the water vapor.vapor.

The StratosphereThe Stratosphere

Here very strong Here very strong eastward winds called eastward winds called the jet streams reach the jet streams reach speeds of 320 km per speeds of 320 km per hour. The jet streams hour. The jet streams move faster in the move faster in the winter than in the winter than in the summer helping summer helping storms move across storms move across the United States.the United States.

The stratosphere extends from the troposphere to The stratosphere extends from the troposphere to an altitude of about 50 km.an altitude of about 50 km.

In the lower stratosphere, the temperature is In the lower stratosphere, the temperature is around –60 degrees C. around –60 degrees C.

The MesosphereThe Mesosphere In the mesosphere, 50-90km above the earth, the In the mesosphere, 50-90km above the earth, the

temperature begins to decrease to –100 degrees temperature begins to decrease to –100 degrees C.C.

The upper region is the coldest. If water vapor is The upper region is the coldest. If water vapor is present thin clouds of ice form, noctilucent.present thin clouds of ice form, noctilucent.

The mesosphere The mesosphere protects the Earth from protects the Earth from meteoroids. When they meteoroids. When they reach the mesosphere, reach the mesosphere, they burn up from the they burn up from the friction of rubbing friction of rubbing against the particles of against the particles of gas.gas.

The ThermosphereThe Thermosphere

The thermosphere begins above the mesosphere The thermosphere begins above the mesosphere at a height of about 90 km.at a height of about 90 km.

The air is very thin. The density of the The air is very thin. The density of the atmosphere and the air pressure are one ten-atmosphere and the air pressure are one ten-millionth of what they are at the Earth’s surface.millionth of what they are at the Earth’s surface.

The temperature is very high in this layer because The temperature is very high in this layer because the rays from the sun are absorbed in this layer.the rays from the sun are absorbed in this layer.

Heat- sphereHeat- sphere

Thermosphere means heat-sphere. The Thermosphere means heat-sphere. The temperatures reach 2000 degrees temperatures reach 2000 degrees C.because this layer absorbs the ultraviolet C.because this layer absorbs the ultraviolet radiation from space and convert it into heat.radiation from space and convert it into heat.

A thermometer placed in the thermosphere A thermometer placed in the thermosphere would register below 0 because the particles would register below 0 because the particles are so far apart that not enough of them are are so far apart that not enough of them are present to bombard a thermometer.present to bombard a thermometer.

IonosphereIonosphere

Within the mesosphere and the Within the mesosphere and the thermosphere is a layer of electrically thermosphere is a layer of electrically charged particles called the Ionosphere. It charged particles called the Ionosphere. It allows radio waves to travel around the allows radio waves to travel around the earth. earth.

The ExosphereThe Exosphere The upper thermosphere is called the The upper thermosphere is called the

exosphere.exosphere. The exosphere extends from 550 km above The exosphere extends from 550 km above

the surface for thousands of km.The air is the surface for thousands of km.The air is very thin.very thin.

Artificial satellites orbit in the exosphere.Artificial satellites orbit in the exosphere.

Atmospheric PressureAtmospheric Pressure Air pressure is caused by Air pressure is caused by

Earth’s gravity pulling the Earth’s gravity pulling the air particles toward the air particles toward the Earth. Earth.

As you move away from As you move away from the Earth, air pressure the Earth, air pressure decreases.decreases.

Jets that fly in the Jets that fly in the stratosphere need stratosphere need pressurized cabins for pressurized cabins for the passengers.the passengers.

Temperature in the Temperature in the LayersLayers

The troposphere is warmed mainly by heat The troposphere is warmed mainly by heat from the ground.from the ground.

The air temperature decreases 6.5The air temperature decreases 6.5º every º every kilometer you climb up.kilometer you climb up.

The sun is the source of energy The sun is the source of energy for Earth. As the sun’s light for Earth. As the sun’s light passes through the layers some passes through the layers some layers contain gases that layers contain gases that absorb the energy. absorb the energy.

Ozone LayerOzone Layer

Most of the ozone in the atmosphere is Most of the ozone in the atmosphere is found between 16 km and 60 km about the found between 16 km and 60 km about the surface of the Earth. Most are between 35 surface of the Earth. Most are between 35 and 60 km.and 60 km.

Ozone molecules absorb much of the het Ozone molecules absorb much of the het and uv rays from the sun..and uv rays from the sun..

Ozone shields the Earth from ultraviolet Ozone shields the Earth from ultraviolet radiation. radiation.

CFCsCFCs

Chlorofluorocarbons are chemical compounds Chlorofluorocarbons are chemical compounds used in refrigerators, air conditioners and aerosol used in refrigerators, air conditioners and aerosol cans. This enter the atmosphere and break the cans. This enter the atmosphere and break the bond of the three oxygen molecules that from bond of the three oxygen molecules that from ozone.ozone.

One of the chlorine molecules combines with one One of the chlorine molecules combines with one of the three oxygen atoms, leaving a two atom of the three oxygen atoms, leaving a two atom molecule.molecule.

These new atoms do not absorb ultraviolet rays.These new atoms do not absorb ultraviolet rays.

Hole in the Ozone LayerHole in the Ozone Layer

The destruction of The destruction of ozone molecules by ozone molecules by CFCs seems to cause CFCs seems to cause a seasonal reduction in a seasonal reduction in ozone over Antarctica ozone over Antarctica called the Ozone hole.called the Ozone hole.

Ozone concentration is Ozone concentration is lowest in October in lowest in October in this location.this location.

Water CycleWater Cycle

The three steps of The three steps of the water cycle are the water cycle are evaporation and evaporation and transpiration, transpiration, condensation and condensation and precipitation.precipitation.

EvaporationEvaporation

Evaporation occurs when heat from the Evaporation occurs when heat from the sun causes water to change from a sun causes water to change from a liquid to a gas.liquid to a gas.

CondensationCondensation

If the water vapor or gas is cooled enough it If the water vapor or gas is cooled enough it will change back into a liquid.will change back into a liquid.

The process of vapor changing back into a The process of vapor changing back into a liquid is called condensation.liquid is called condensation.

Clouds form when condensation occurs.Clouds form when condensation occurs. Clouds are made of tiny drops of water that Clouds are made of tiny drops of water that

collect to form larger drops.collect to form larger drops.

PrecipitationPrecipitation

As water drops grow in a cloud, they will As water drops grow in a cloud, they will become heavy enough to fall to Earth as become heavy enough to fall to Earth as precipitation. precipitation.

Air MovementAir Movement

Uneven heating of the earth due to the Uneven heating of the earth due to the curved surface of the globe produces winds. curved surface of the globe produces winds.

Wind is the movement of air from an area of Wind is the movement of air from an area of higher pressure to an area of lower higher pressure to an area of lower pressure.pressure.

Uneven Heating of the EarthUneven Heating of the Earth Cold dense air from the poles sinks and Cold dense air from the poles sinks and

moves toward the poles.moves toward the poles. The hot less dense air near the equator is The hot less dense air near the equator is

pushed up and moves back toward the pushed up and moves back toward the poles.poles.

Coriolis EffectCoriolis Effect

The rotation of the The rotation of the Earth causes moving Earth causes moving air and water to air and water to appear to turn to the appear to turn to the right north of the right north of the equator and to the equator and to the left south of the left south of the equator.equator.

Global Wind BeltsGlobal Wind Belts

The Coriolis Effect and The Coriolis Effect and differences in solar differences in solar radiation creates wind radiation creates wind patterns on earth, patterns on earth, known as Wind Belts.known as Wind Belts.

We live in the We live in the prevailing Westerlies prevailing Westerlies where winds move where winds move west to east.west to east.