Earth’s Atmosphere

Chapter 15-1

Objectives:Objectives: Identify the gases in the atmosphere.Identify the gases in the atmosphere. Describe the structure of the atmosphere.Describe the structure of the atmosphere. Explain what causes air pressure.Explain what causes air pressure.

Atmosphere

The atmosphere is a thin layer of gases that The atmosphere is a thin layer of gases that surround the Earth.surround the Earth.

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

The Past Atmosphere

It 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.

Earth’s early atmosphere was produced by Earth’s early atmosphere was produced by erupting volcanoes and contained nitrogen erupting volcanoes and contained nitrogen and carbon dioxide, but very little oxygen.and carbon dioxide, but very little oxygen.

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

Ozone Layer

The oxygen that was left behind joined The oxygen that was left behind joined together, in sets of three, to form a gas together, in sets of three, to form a gas known as ozone.known as ozone.

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

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

Oceans

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 organisms that lived far below the surface of the oceans.of the oceans.

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

Blue-green Bacteria

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

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

Oxygen

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 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 Atmosphere

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

the atmosphere.the atmosphere. Oxygen accounts for 21 percent.Oxygen accounts for 21 percent. The remaining 1 percent is a combination of The remaining 1 percent is a combination of

carbon dioxide, water vapor, argon and carbon dioxide, water vapor, argon and trace gases.trace gases.

The trace gases include neon, helium, The trace gases include neon, helium, krypton and xenon.krypton and xenon.

Solid 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 Atmosphere

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

Air Pressure

The layers of air that surround the Earth are The layers of air that surround the Earth are held close to it by the force of gravity.held close to it by the force of gravity.

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

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

The 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 Weather occurs in this layer. Life occurs in

the troposphere.the troposphere. The height of the troposphere varies from The height of the troposphere varies from

the Equator to the poles. (17-8 km)the Equator to the poles. (17-8 km) It is highest at the equator.It is highest at the equator. This layer contains 99% of the water vapor.This layer contains 99% of the water vapor.

The Stratosphere

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.

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

Ionosphere

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 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 C.temperature begins to decrease to –100 degrees 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, noctillucent.present thin clouds of ice form, noctillucent.

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

The Thermosphere

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

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

The 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 Pressure

Air pressure is caused by Earth’s gravity Air pressure is caused by Earth’s gravity pulling the air particles toward the Earth. pulling the air particles toward the Earth.

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

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

Temperature in the Layers

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

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.

Temperature of Layers

Ozone 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.

CFCs

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 Layer

The destruction of The destruction of ozone molecules by ozone molecules by CFCs seems to cause a CFCs seems to cause a seasonal reduction in 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.

Chapter 15-2

Objectives:Objectives: To describe what happens to the energy the To describe what happens to the energy the

Earth receives form the Sun.Earth receives form the Sun. To compare and contrast radiation, To compare and contrast radiation,

conduction and convection.conduction and convection. To explain the water cycle and its effect on To explain the water cycle and its effect on

weather patterns.weather patterns.

Energy Transfer in the Atmosphere

Energy Transfer

Energy is transferred by the means of Energy is transferred by the means of conduction, convection and radiation.conduction, convection and radiation.

Radiation

Radiation is energy that is transferred in the Radiation is energy that is transferred in the form of rays or waves. form of rays or waves.

Earth radiates some of the energy it Earth radiates some of the energy it receives and absorbs from the Sun back receives and absorbs from the Sun back toward space.toward space.

Conduction

Conduction is the transfer of energy that Conduction is the transfer of energy that occurs when molecules bump into one occurs when molecules bump into one another.another.

When objects are in contact, energy is When objects are in contact, energy is transferred from warmer objects to cooler transferred from warmer objects to cooler objects.objects.

Convection

Convection is the transfer of heat by the Convection is the transfer of heat by the flow of materials. flow of materials.

Convection currents carry heat through the Convection currents carry heat through the air as cold air sinks and warm air rises.air as cold air sinks and warm air rises.

Water 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.

Evaporation

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.

Condensation

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.

Precipitation

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.

Chapter 15-3

Objectives:Objectives: Explain why different latitudes on Earth Explain why different latitudes on Earth

receive different amounts of solar energy.receive different amounts of solar energy. Describe the Coriolis effect.Describe the Coriolis effect. Explain how land and water surfaces affect Explain how land and water surfaces affect

the overlying air.the overlying air.

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

Uneven Heating of the Earth

Cold dense air from the poles sinks and Cold dense air from the poles sinks and moves toward the equator.moves toward the equator.

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 Effect

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

Global Wind Belts

The Coriolis Effect The Coriolis Effect and differences in and differences in solar radiation solar radiation (temperature) creates (temperature) creates wind patterns on earth, wind 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.

Jet Stream

The Doldrums The windless rainy zone near the equator is The windless rainy zone near the equator is

also called the doldrums.also called the doldrums. Near the equator the Sun heats the air and Near the equator the Sun heats the air and

causes it to rise, creating low pressure and causes it to rise, creating low pressure and little wind. The rising air cools, causing little wind. The rising air cools, causing rain.rain.

The Trade Winds

Near the 30Near the 30ºNorth and South line of latitude ºNorth and South line of latitude air creates steady winds that blow in air creates steady winds that blow in tropical regions.tropical regions.

Sailors used these winds to create trade Sailors used these winds to create trade routes.routes.

Prevailng Westerlies

Between 30Between 30º and 60º lines of latitudes the º and 60º lines of latitudes the winds blow from west to east, in opposite winds blow from west to east, in opposite directions from the trade winds.directions from the trade winds.

These winds affect weather patterns in the These winds affect weather patterns in the United States.United States.

Polar Easterlies

Above 60Above 60º line of latitude, the winds move º line of latitude, the winds move from east to west and are called the Polar from east to west and are called the Polar Easterlies.Easterlies.

Sea and Land Breeze

During the day, land heats During the day, land heats up faster than the ocean.up faster than the ocean.

As the warm air over the As the warm air over the land rises it is replaced land rises it is replaced with cool breezes from the with cool breezes from the ocean.ocean.

The opposite occurs at The opposite occurs at night.night.