Global Atmospheric Change
Modeling Earth's Atmosphere
The air surrounding Earth is known as the atmosphere. Gas molecules in the atmosphere are held relatively close to Earth’s surface by gravity. The atmosphere is mostly nitrogen (78%) and oxygen (20%). The amount of water vapor in the atmosphere varies, but can be as much as 5% by volume. Other gases, present in much smaller amounts, also are extremely important parts of the atmosphere. Carbon dioxide (CO2), methane (CH4) and other gases, including water vapor, help radiate heat back toward Earth’s surface, thus keeping it much warmer than it would be otherwise. Ozone, which is present in tiny amounts in part of the atmosphere, filters out most of the harmful ultraviolet radiation from the sun.
Life on Earth would not be possible without the atmosphere, which protects the planet’s surface from extremes of temperature and harmful radiation, and also provides essential water, carbon dioxide, oxygen and nitrogen. This activity helps students learn about Earth’s atmosphere by creating a scale model.
In the atmosphere model created by students, 1 cm represents 0.5 km. Based on these proportions, the diameter of the Earth would have to be drawn as approximately 25,000 cm. The sun would be positioned 300,000,000 cm away!
Ozone, a highly reactive gas molecule made of three oxygen atoms, is found naturally in the stratosphere. Even though it is present only in tiny amounts, ozone is vital to the planet. It absorbs most of the harmful ultraviolet radiation emitted by the sun and prevents it from reaching Earth’s surface. Near the ground, ozone often is produced as a byproduct of burning fossil fuels. Unfortunately, in this instance, ozone is very harmful. It can damage lungs and is harmful to other living things, such as plants.
Ask students if they ever have seen pictures of astronauts in space. Ask, Why do the astronauts wear special suits? Mention that the space suits keep astronauts warm, provide them with air to breathe and protect them from harmful rays from the sun. Follow by asking if we need to wear space suits on Earth. Help students recognize that the thin layer of gases surrounding Earth—the atmosphere—provides protection for all of the planet, as space suits protect the astronauts.
Mention that, as a class, the students will create a scale model of Earth’s protective layer of gases. Lay a sheet of brown or white paper (at least 2.5 m long) on the floor where students can work on it. Discuss the scale of the model with students (1 cm = 1/2 km; 2 cm = 1 km).
Distribute the Job cards to student groups. Each group will create and decorate a different part of the atmosphere model. Older students should measure and draw their own lines on the model. To facilitate work in groups, you may want students to cut off their sections of the model to complete in separate locations. (Groups 1 and 2 work on the same section.) Once completed, the sections can be taped together.
Group 1 – Planet Earth. Draws a vertical line about 15 cm from the bottom of the sheet of paper (this line represents the Earth’s surface); creates figures (mountains, forests, cities, etc.), using construction paper or other materials and adds them to the model. Remind students that the figures they create should be no more than 5 cm tall
Group 2 – First layer of the atmosphere (troposphere). Draws a line about 22 cm from the line designating Earth’s surface (represents the upper limit of the first layer); adds figures of weather phenomena (clouds, rain, lightning, etc.), as well as low-flying aircraft and hot air balloons. Point out to students that much of the pollution produced by burning wood and fossil fuels remains in the troposphere. The gases responsible for keeping Earth warm (greenhouse gases) are found in this layer. Temperatures within the troposphere decrease with altitude.
Group 3 – Second layer of the atmosphere (stratosphere). Draws a line about 100 cm from the line for the Earth’s surface (represents the upper limit of the second layer); adds figures of storm clouds, jet aircraft, wind, and a representation of the protection provided by ozone molecules in this layer. The stratosphere is warmer due to absorption of UV light by ozone.
Group 4 – Third layer of the atmosphere (mesosphere). Draws a line about 170 cm from the line for the Earth’s surface (represents the upper limit of the third layer); adds figures of feathery ice clouds and weather balloons. The mesosphere is very cold.
Group 5 – Fourth layer of the atmosphere (thermosphere). Adds figures of spacecraft, satellites and meteors (shooting stars) to the model. If students were to draw a line, the upper limit of the thermosphere would be 1,200 cm (12 m) from the baseline of the model. This group may use the remainder of the space on the sheet. This layer is very hot in some parts—up to 1,700°C or more—due to absorption of radiation by different atoms and molecules.
Group 6 – Outer Space. Creates figures representing other components of the solar system and universe, and places them around the room. The exosphere contains very small amounts of hydrogen and helium, and continues until it merges with space.
Have each group label its layer on the model. Display the model somewhere in the classroom. Encourage students to note that most activities involving the atmosphere occur very close to Earth’s surface. Leave the model available for students to refer to throughout the unit.
Keywords: atmosphere | climate | CO2 | Earth | ecology | energy | environment | global change | greenhouse gas | oxygen | ozone | physical science | radiation | solar energy | sun | weather | lesson
- Moreno, N., Tharp, B., and Dresden, J. (2011) The Science of Global Atmospheric Change Teacher’s Guide. Baylor College of Medicine: Houston. ISBN: 978-1-888997-75-0.
- Photo courtesy of NASA.
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Funded by the following grant(s)
My Health My World: National Dissemination
Grant Number: 5R25ES009259
The Environment as a Context for Opportunities in Schools
Grant Number: 5R25ES010698, R25ES06932
Foundations for the Future: Capitalizing on Technology to Promote Equity, Access and Quality in Elementary Science Education