The Earth: An Interdisciplinary Unit
- Grades: 6–8
Aims and Objectives
- understand that Earth is a planet in constant motion
- understand that Earth is a planet constantly being
formed and transformed
- explore basic principles of geology
- develop an enthusiasm for investigating landscape
- collect, observe and classify rock samples
- understand that most materials come from Earth and its
- devise initiatives to care for Earth and save natural
- develop rational and creative thinking skills
- work co-operatively in groups
- Following directions
Before the unit, gather the following resources:
- books and charts in the classroom
- globe of Earth, candle
- hard-boiled egg, knife
- balloons, newspaper, paint, thin card, felt-tip pens,
- container with deep sides
- wire, plastic wrap, soil, rocks, pebbles, sand
- paper plates
- glass jars, string, paper clips, salt, sugar
- tongs, access to a hot plate
- deep-sided plastic tray
- large sheets of plain chart paper
- reference materials
atmosphere: the mixture of gases surrounding Earth
bedrock: solid rock under the soil
continent: a large land mass
core: the innermost part of Earth's structure
crust: the outermost part of Earth's structure
earthquake: a shaking of Earth's surface caused by the movement of tectonic plates
erosion: when the rocks and soil of Earth's surface are loosened, worn away and moved
evaporation: the process of turning a liquid into vapor
geologist: a person who studies the structure, composition and history of Earth
igneous: rock formed from cool magma or lava
island: an area of land surrounded by water
mantle: the part of Earth's structure between the crust and the core
metamorphic: a rock altered by pressure, heat or chemically active fluids
mineral: a natural substance, such as a rock, that is not of animal or plant origin
ocean: a great mass of salt water
plain: a large, flat area of land
plate: large pieces of moving rock in Earth's crust
sedimentary: rocks composed of different layers deposited by water, wind or ice
soil: loose covering, of broken rocky material and decaying organic matter, over Earth's surface
valley: area of low land between two mountains
volcano: vent in earth's crust
The Living Planet
Earth is the only planet on which life is known to exist. It is uniquely suited to life because it is warmed by the nearby Sun, it is surrounded by a life-supporting atmosphere, it has a large supply of air and water, and there are plenty of minerals in its crust
Earth in Space
- Earth is the third planet from the Sun.
- Earth is not quite a sphere. It is flattened slightly at the poles
- The circumference of Earth at the equator is 40,075.02
- The estimated area of Earth's surface is 510,065,600
- A true day (i.e., the time it takes for Earth to rotate on its axis) on Earth is 23 hours 56 minutes 4.0996 seconds.
- It takes Earth 365 days 5 hours 48 minutes and 46 seconds to orbit the Sun.
- Earth orbits the Sun at an average speed of 30 km per second.
- Earth experiences changing seasons because it orbits the Sun at an angle.
- Earth has one satellite, the Moon.
The Structure of the Earth
Earth is thought to consist of:
- an inner core about 2600 km in diameter made of solid iron and nickel.
- an outer core about 2250 km thick made of molten iron and nickel.
- a mantle of solid rock about 2900 km thick.
- a crust about 6-70 km thick.
The crust and the top layer of the mantle form about twelve major moving tectonic plates.
Earth is surrounded by an atmosphere made up of 78.09 per cent nitrogen, 20.95 oxygen, 0.93 per cent argon and 0.03 per cent carbon dioxide, plus small mounts of neon, helium, krypton, hydrogen, xenon, ozone and radon.
- Earth is about 4600 million years old.
- The closer to the center of Earth, the greater the temperature and the air pressure. At the center of the core
the estimated temperature is 4500 degrees Celsius.
- Life is believed to have begun on Earth about 4000
million years ago.
- Millions of years ago Antarctica was a rainforest.
- About 71 per cent of Earth's surface is covered by water.
- The Atlantic Ocean is growing about 2.5 cm wider each year. The Pacific Ocean is shrinking.
- About 400 earthquakes rock New Zealand every year.
- A rock from an active volcano might be about 1000 degrees Celsius. That's a bit too hot to handle!
- Australia has no active volcanoes.
- Seashells can be found high up on some mountains. The mountains were pushed up millions of years ago as Earth's crust folded and crumpled. They carried rocks and fossil shells up from the seabed.
- A person who explores and maps the inside of caves is called a spelunker.
- Stalactites hang from the ceiling of caves. Stalagmites rise up from the cave floor.
- It takes about 1000 years to make 2.5 cm of soil.
- Sedimentary rocks cover more than two-thirds of Earth's surface.
- At present, people can drill only a few kilometers into Earth's crust.
- If we could dig all the way to China we would have to start in Chile or Argentina. China and these two countries are Antipodes — places opposite each other on the globe.
Create word banks to display in the classroom. Encourage students to add words as the unit progresses. One word bank could list students' feelings or impressions about Earth. Use the banks as a basis for language and word study.
Discuss with students the facts they already know about Earth. Use the students' comments to create "What we know about Earth" and "What we want to know about Earth" charts. Write students' initials next to their comments and review and add to the charts regularly.
Have students write acrostic Earth poems, for example:
A ll together
R acing through space
T here's room for us all
H ere on _.
Students could use words collected in the word banks. Have students design posters for their poems and present them to the rest of the class. Discuss any rhyme, rhythm, alliteration, word choice, line pattern or illustration that is appropriate.
This activity could be used for evaluation if repeated at the end of the unit. How have students' attitudes towards Earth and their feelings and knowledge about Earth changed and developed?
Earth in Space
Examine a globe of Earth. Ask students to observe and explain the way Earth spins on its axis. (Earth rotates on its axis and the plane of its orbit is inclined at an angle of 23.5 degrees.)
Earth Orbits the Sun
Simulate Earth orbiting the Sun. Use a globe and put a sticker on the United States. Place a candle in the middle of the floor to represent the Sun.
Explain to students that the candle Sun and the globe Earth are not in correct proportion. Have a student carry the globe and walk around the 'Sun,' at the same time rotating Earth on its axis. Encourage students to observe day and night in the U.S. as Earth rotates on its axis, and the changing seasons as Earth completes one orbit of the Sun.
If you want to get really complicated, you could ask another student to be the Moon and walk around Earth as it rotates and orbits the Sun! The Moon takes the same time to complete one orbit of Earth as it does to complete one rotation on its axis. One side is therefore turned permanently to Earth. The Moon reflects light from the Sun. Encourage students to draw conclusions about the phases of the Moon, from new moon (dark), to crescent moon (first quarter half moon), full moon and back again to new moon.
Explain to students that the rise and fall of the ocean twice a day is called a tide. Ask them to thin about how high the water is on the beach at one time of the day and then how low it is at another time of the day. Tides are caused by the force of the moon's gravity pulling on Earth. Encourage students to draw conclusions about the progression of the tides around Earth as it rotates. The average time between high tides is 12 hours and 25 minutes.
Earth is Like a Hard-Boiled Egg!
Use a hard-boiled egg to demonstrate the structure of Earth. Tell students that Earth has layers inside it. Slice the egg in half. The eggshell is like the rocky crust of Earth. The egg white is like the solid rock mantle. The yolk is like the molten outer core and the solid inner core.
Have students make papier-mâché models of the structure of Earth. Cover an inflated balloon with layers of papier-mâché. When the model is strong and dry, carefully cut away a cross-section. Cut a circle of thin card that will fold in half and fit into this cross-section. Use felt-tip pens to draw on the layers inside Earth. Fit this inside view into the cut-away section and attach with tape. Paint the outside of Earth. Suspend the models from the ceiling or display them with appropriate labels.
Find the Antipodes
Antipodes are places opposite each other on the globe. For example, the South Pole is opposite the North pole, China is opposite Chile. Have students find the antipodes of their home.
Here is a formula:
1. Find the latitude of your home and change its direction For example, if the latitude is south, make it north
2. Find the longitude and subtract it from 180 then change its direction. For example, if the longitude is east, make it west
3. You now have the latitude and longitude of the opposite point on the globe.
Students could then choose a point on the globe to start digging. Where would they end up if they could dig right through Earth?
Create Earth's Atmosphere
Have students look at a globe or maps and estimate the proportion of Earth's surface that is covered with water. They should conclude that the surface of Earth is mostly water. In fact, about 71 percent of Earth's surface is covered with water.
Encourage students to use this knowledge when constructing their own working model of Earth's surface and its atmosphere. Have each group arrange soil, rocks and water in a deep-sided container. Use wire to make a frame for the top of the dish and cover this with plastic wrap to represent Earth's sealed atmosphere. Have each group record their observations over the next few weeks. They could observe and comment on any changes to their model Earth — evaporation, condensation, plant growth and so on.
Explain that the crust of Earth is made up of large plates of rock that might be covered by sand, soil or water. These rock plates are always moving. They move about 2 to 15 cm every year. That's about the same amount as a fingernail grows. Have each student cut a paper plate in half. Tape a rectangle of paper on top.
Have students experiment by sliding one side of the plate under the other. The paper rectangle will rise. Over millions of years, mountains form in the same way. Earthquakes occur when the creeping plates get stuck. Pressure builds until the plates suddenly slip, releasing Earthquake energy.
Sedimentary rocks cover more than two-thirds of Earth's surface. They are made up of different layers. These layers might be sand, silt, pebbles or fossil fragments. Over a long period of time the layers turn to rock.
Have students make a model of sedimentary layers. Have students collect rocks, pebbles, dirt, sand and other materials and, either individually or in small groups, fill about one-third of the jar with their collected materials. Add water, screw on the lid and shake well. Have students observe what happens over the next day or so as the materials settle into layers. Encourage students to describe the layers. For example, "The heavy, coarse materials are at the bottom and the fine or light materials are at the top."
Igneous rocks are formed from cooling magma or lava. The mixture of minerals and how quickly they cool determines the different types of igneous rock formed. Slow cooling produces large crystals. Rapid cooling results in small crystals.
Have students grow their own crystals. Cool some quickly (place in a freezer or a fridge) and others slowly (place in sunlight or at room temperature). Have students examine the crystals with a magnifying glass, then draw and compare them.
To grow crystals, mix salt or sugar in half a glass of boiling water until no more will dissolve. Tie a paper clip to the end of a piece of string to weight it. Drop the weight into the salt or sugar solution and hang the other end over the side of the glass. Leave the glass undisturbed for the crystals to grow on the string.
Metamorphic rocks are formed when already existing rocks are altered by pressure (as tectonic plates stress, strain and squeeze) or heat (from nearby magma).
Have students write a recipe for a metamorphic rock, using shale, sandstone or limestone as the main ingredient. Depending on depth and heat, the shale will become slate, schist, gneiss or homfels. The sandstone will become quartzite and the limestone will become marble.
Collecting and Classifying Rocks
Organize a rock-collecting expedition in a park or in the playground. If possible, first find a geological guidebook for your area. Have students find as many different rock specimens as they can. Students can use a rock classification sheet to classify their specimens as igneous, sedimentary or metamorphic. The description column might include observations about where the rock was found, its shape, color or texture.
For the classification sheet, include the following elements:
- very hard
- crystals of each mineral lined up in layers
Have students observe the effects of heat and cold on rocks. Place small specimens of different rocks on a hot plate for at least ten minutes. Use a pair of tongs to place the hot rocks one at a time into a dish of ice-water. Record the results. The heat will cause the rocks to expand, and the cold will cause them to contract. Sedimentary rocks weather faster because they are softer and more porous.
Make a mount of sand or dirt towards one end of a deep-sided plastic tray. Have students place pebbles, flowers, twigs, leaves and other natural materials on the slope of the mound. Have students hypothesize about what will happen if water is poured down the slope. Pour some water slowly, then quickly, and observe what happens. Encourage students to conclude that Earth's surface is constantly being changed.
Air and water can weather or change rocks to make soil. Changes in temperature also cause rocks to crack and crumble. Have students rub two rocks against each other and collect the particles in a jar. They could also put a rock in an old pillowcase and hammer it until it is crushed. Add bits of dead leaves, grass and other organic material.
How long does it take students to make one cup of soil? (It takes nature up to a thousand years to make 2.5 cm of soil.)
The Resourceful Earth
Earth's crust is rich in mineral resources. People mine these resources and process them so that they can use them. Encourage students to do research on some of the Earth's mineral resources and their uses, e.g., bauxite, gold, silver, coal, iron ore, sand.
Students might choose one resource and create a flow chart to explain the process from mining to final product.
Organize a debate on the topic that '"People use too much of Earth's resources by consuming products unnecessarily."
Students could design a series of posters to encourage people to take care of Earth and its resources.
Inside Earth: A Simulation
Use as a Final Project to Your Unit
The government announced today a special Inside Earth mission. Five carefully selected teams will attempt to dig through the center of Earth from five different starting points. Each team will be made up of the following specialist crew:
- Survey and chart the area where digging will commence
- Note any special features or formulations.
- Analyze weather conditions.
- Design the vehicle to carry the team officer inside Earth.
- Build a prototype model.
- Write operating instructions.
Create a Design Brief Reproducible for the Transporter using the elements below:
- Plan and organize all supplies needed for the mission (including food, clothing and equipment).
- Keep the mission log.
- Record any discoveries.
- Record life on board the mission vehicle.
- Record any discoveries.
Organize teams and ensure that there is at least one student in each team responsible for each crew job. Each team should examine a globe or map of the world and decide where they will start their mission. The landforms and other physical features at this starting point will determine the design of their vehicle, supplies needed and other mission outcomes.
Each team should then use their imaginative, creative thinking and problem-solving skills to undertake their tasks. Their work might include models, diaries, reports, newspaper articles, charts, scrapbooks or photograph albums. At the end of the mission each team should complete a mission report and prepare a presentation for the whole class.
For the mission report, include the following elements:
Bresler, Lynn. The Usborne Book of Earth Facts. Usborne. Packed with fascinating facts to capture the interest of students.
Symes, Dr. R.F. Rock and Mineral. (Eyewitness Guide series). HarperCollins. A book of stunning real-life photographs with captions to tell the story of Earth.
Cole, Joanna. The Magic School Bus Inside Earth. Ashton Scholastic. Ms. Frizzle takes her class on an excursion to the center of Earth. Zany illustrations and humorous fantasy are combined with a fantastic lesson in geology.
Maddern, Eric. Earth Story. HarperCollins. Explores the creation of Earth.
Andrew, Kate. Beyond the Rolling River. Lions. The search for the tuning fork that controls Earth's weather.
Hughes, Ted. The Iron Man. Faber. A giant Iron Man emerges from inside Earth.
Fantasia. Walt Disney. "Rite of Spring" section. The animation of this section shows the formation of Earth and the beginning of life.
If You Could See Earth. Britannica. (9 mins.) Satellite footage shows Earth, continents and oceans. The rotation of Earth and the forces of gravity are also explained.
Nature of Australia. ABC. (Two video set -- 150 min.) An account of how the island continent of Australia came to be the way it is.
Our Dynamic Earth. National Geographic. (23 mins.) More suitable for older students. Explains the theory of plate tectonics and includes live footage of earthquakes and volcanoes.
Adapted from "The Earth," Senior Topics. Published by Ashton Scholastic in Australia.