Ch. 22

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atmosphere a mixture of gases that surrounds a planet, such as EarthThe most abundant elements in air are the

gases nitrogen, oxygen, and argon.The two most abundant compounds in air are

the gases carbon dioxide, CO2, and water vapor, H2O.

Nitrogen in the AtmosphereNitrogen makes up about 78% of Earth’s

atmosphere and is maintained through the nitrogen cycle.

Nitrogen is removed from the air mainly by the action of nitrogen-fixing bacteria.

Decay releases nitrogen back into the atmosphere.

Oxygen in the AtmosphereOxygen makes up about 21% of Earth’s

atmosphere.Land and ocean plants produce large

quantities of oxygen in a process called photosynthesisAnimals, bacteria, and plants remove oxygen

from the air as part of their life processes.

Composition of the AtmosphereWater Vapor in the AtmosphereAs water evaporates from oceans, lakes,

streams, and soil, it enters air as the invisible gas water vapor.

Plants and animals give off water vapor during transpiration, one of their processes. But as water vapor enters the atmosphere, it is removed by the processes of condensation and precipitation.

Composition of the AtmosphereOzone in the Atmosphereozone a gas molecule that is made up of three

oxygen atomsOzone in the upper atmosphere forms the ozone

layer, which absorbs harmful ultraviolet radiation from the sun.

Without the ozone layer, living organisms would be severely damaged by the sun’s ultraviolet rays.

Unfortunately, a number of human activities damage the ozone layer.What are some “activities” that damage our ozone?

Composition of the AtmosphereParticulates in the AtmosphereParticulates can be volcanic dust, ash from

fires, microscopic organisms, or mineral particles lifted from soil by winds.

Layers of the AtmosphereEarth’s atmosphere as a distinctive pattern of

temperature changes with increasing altitude.

Scientists identify four main layers of the atmosphere based on these differences.The TroposphereThe StratosphereThe MesosphereThe Thermosphere

The Tropospheretroposphere - the lowest layer of the

atmosphere, in which temperature drops at a constant rate as altitude increases; the part of the atmosphere where weather conditions exist

The Stratosphere

stratosphere the layer of the atmosphere that lies between the troposphere and the mesosphere and in which temperature increases as altitude increases; contains the ozone layer

The Mesosphere

mesosphere the coldest layer of the atmosphere, between the stratosphere and the thermosphere, in which the temperature decreases as altitude increases

The upper boundary of the mesosphere, called the mesopause, has an average temperature of nearly 90°C, which is the coldest temperature in the atmosphere.

The Thermosphere

thermosphere the uppermost layer of the atmosphere, in which temperature increase as altitude increases; includes the ionosphere

Ionosphere - The lower region of the thermosphere, at an altitude of 80 to 400 km

Interactions between solar radiation and the ionosphere cause the phenomena known as auroras.What is an aurora???

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Pop Quiz1. Which layer of the atmosphere is the

coldest, reaching -90C?

A. TroposphereB. StratosphereC. MesosphereD. Thermosphere

2. In what layer of the atmosphere does weather conditions exist?

A. Troposphere B. StratosphereC. MesosphereD. Thermosphere

3. In which layer of the atmosphere does the ozone layer exist?

A. Troposphere B. StratosphereC. MesosphereD. Thermosphere

4. What is the most common element that makes up our atmosphere?

A. OxygenB. NitrogenC. Carbon DioxideD. Hydrogen

5. Land and ocean plants produce large quantities of oxygen in a process called what?

A. PhotosynthesisB. transpirationC. evaporationD. Absorption

6. Which part of the atmosphere absorbs harmful ultraviolet radiation from the sun?

A. ThermosphereB. MesosphereC. Ozone LayerD. Ionosphere

RadiationAll of the energy that Earth receives from the

sun travels through space between Earth and the sun as radiation.

Radiation includes all forms of energy that travel through space as waves.

Radiation can take several forms but the most common is light (electro-magnetic radiation).

Light radiation is categorized by its wavelength. The shorter the wave length the more energetic (and dangerous).

The Earth’s atmosphere protects us from the harmful radiations by absorbing the energy of the light radiation.

Different layers of the atmospheres absorb different wavelengths of radiation.

The Exosphere and Thermosphere absorb high energy X-Ray and UV Rays

The Mesosphere absorbs very little.

The Stratosphere absorbs mid-energy UV Rays

The Troposphere absorbs low energy Infra Red Radiation

Electromagnetic Spectrum…electromagnetic spectrum - all of the

frequencies or wavelengths of electromagnetic radiation

The distance from any point on a wave to the identical point on the next wave, for example from crest to crest, is called the wavelength of a wave.

The various types of radiation differ in the length of their waves.

The diagram below shows the varying waves of the electromagnetic spectrum.

Reflectionalbedo the fraction of solar radiation that is

reflected off the surface of an object.Reflection - the return of light, heat, sound,

etc., after striking a surface. The amount of energy that is absorbed or

reflected depends on characteristics such as color, texture, composition, volume, mass, transparency, state of matter, and specific heat of the material on which the solar radiation falls.

AbsorptionSolar radiation that is not reflected is

absorbed by rocks, soil, water, and other surface materials.

The absorption of thermal energy from the ground heats the lower atmosphere and keeps Earth’s surface much warmer than it would be if there were no atmosphere.

The Greenhouse Effectgreenhouse effect the warming of the

surface and lower atmosphere of Earth that occurs when carbon dioxide, water vapor, and other gases in the air absorb and reradiate radiation

Earth’s atmosphere slows the escape of energy that radiates from Earth’s surface.

The diagram below shows the greenhouse effect and the latitude and seasons.

Human Impact on the Greenhouse Effect

Generally, the amount of solar energy that enters Earth’s atmosphere is about equal to the amount that escapes into space.

However, human activities may change this balance and may cause the average temperature of the atmosphere to increase.

Increases in the amount of carbon dioxide may intensify the greenhouse effect and may cause Earth to become warmer in some areas and cooler in others.

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