Plate Tectonics: a full term of science

Ten ready-to-teach lessons for Year 8 Earth and space sciences. Print this pack and the term is prepared: every lesson comes with a step-by-step plan, the questions to ask, a student worksheet, cut-out cards, an evidence sheet or exit tickets, an assessment kit and worked answers.

Start here: five minutes to Monday

1. Skim the term at a glance on the next page.
2. Print the lesson you need. Each lesson is three A4 sheets: plan, worksheet, and cards, an evidence sheet, a map or tickets.
3. Gather the few items under “You need” on the plan. Most come from the science prep room, the kitchen or the garden.
4. Open the free interactive unit on your board or projector. Every plan tells you which picture to show and when.
5. Teach straight from the plan. Timings, talk prompts, misconceptions and worked answers are all on the one page.

For any Year 8 science teacher

The pack suits an earth science specialist and a teacher working outside their own subject alike: each plan explains the idea in plain words, lists the misconceptions students bring, and gives worked answers. The big idea of the term: the Earth’s outer shell is broken into plates that move a few centimetres a year on the slowly creeping mantle. Where plates pull apart, push together or slide past, they build ridges and rift valleys, trenches, volcanoes and mountains, and faults that shake. The theory rests on evidence: fitting continents, shared fossils, the sea floor’s magnetic stripes and the pattern of earthquakes.

Two ways to run each lesson

Every lesson works as one 60-minute block, or as two 30-minute sessions; the split point is marked in every plan. Lessons 3 and 7 need scissors and sticky tape or glue, and Lesson 6 needs a sharp pencil and a steady hand.

Safety and care in one look

The convection model uses hot water from a kettle, handled by the teacher only. Earthquake machines stay on the bench, and rubber bands are pulled along the ruler, never towards a face. Scissors are passed handles first.

The term at a glance

One lesson a week for a term. Each lesson stands on the ones before it, so run them in order where you can.

How the sequence builds

Lessons 1 and 2 set up the Earth’s layers and moving plates. Lessons 3 to 5 take the three kinds of boundary in turn, and Lesson 6 maps where earthquakes and volcanoes happen. Lessons 7 and 8 weigh the evidence, from Wegener’s fossils to the sea floor’s magnetic stripes, Lesson 9 applies it all to the Australian plate, and Lesson 10 brings it together.

Curriculum links (Australian Curriculum V9)

The whole term teaches the Science Understanding descriptor AC9S8U03 quoted on the cover. The lessons also work these Science Inquiry and Human Endeavour descriptors:

Assessment in this pack

• Every plan ends with “Answers and look-fors”: what meeting the idea sounds like in a Year 8 voice, with working.
• The assessment sheet near the front has a class observation checklist and a three-level rubric.
• Lesson 10 is the summative pair: the mystery boundary task, plus the “Show what we know” check.

Materials for the whole term

One gathering session covers all ten lessons. Most of what you need is paper, scissors and rulers; the rest is a few everyday things for the models. One thing is worth doing ahead: test the earthquake machine once, so you know how hard to pull the rubber band for a clear stick and slip.

The one-trip list

• From the prep room: a compass, a bar magnet, stopwatches, metre rulers and a clear tank or large jar.
• From the supermarket: food colouring, a peach or eggs, modelling clay, coarse sandpaper and thick rubber bands.
• From home or the garden: hand towels, a small bottle with a cap, wooden blocks or bricks, and a smooth board.
• From the school: an adding-machine roll or A4 paper, scissors, sticky tape, glue, calculators, a world atlas and a globe.

Safety and care in one look

• Hot water for the convection model comes from a kettle and is handled by the teacher only.
• Rubber bands are pulled along the ruler, never towards a face; bricks stay low on the bench.
• Scissors are passed handles first; offcuts go straight in the bin.
• Damp towels and clay are wiped off benches before the next class.

Assessment without extra work

The term assesses itself. Every lesson plan ends with worked answers and look-fors, and Lesson 10 is the summative pair: the mystery boundary task, in which students plot earthquake depths beside an island chain and explain the sinking plate they reveal, and the final check. This sheet is the place to note what you see along the way.

The three levels

Class observation checklist

A tick a lesson is plenty; the Lesson 10 task and check fill the gaps.

Word wall cards

Cut out the cards and build the wall as the words arrive: crust, mantle and core in Lesson 1; plate, convection and continental drift in Lesson 2; divergent boundary and mid-ocean ridge in Lesson 3; convergent boundary, subduction and trench in Lesson 4; transform boundary, fault and earthquake in Lesson 5; magnitude in Lesson 6; Gondwana in Lesson 7; sea-floor spreading and magnetic stripes in Lesson 8.

Dear families

This term in science, Year 8 studies plate tectonics: how the Earth’s outer shell is broken into plates that move a few centimetres a year, and how their movement builds mountains, opens oceans and causes earthquakes and volcanoes. We also look at the evidence that convinced scientists, from fossils to the magnetic record in the sea floor.

Along the way your student will build a scale model of the Earth’s layers, run an earthquake machine with a brick and a rubber band, plot real earthquakes and volcanoes on a map of our region, and put the ancient supercontinent of Gondwana back together like a jigsaw.

Try this at home

• Look at a world map. Which coastlines look as if they could fit together?
• Find out how far Australia moves in a year, and how much it has moved since your student was born.
• Ask whether anyone in the family has felt an earthquake, here or overseas. Where was it?
• Look up the nearest old volcano to where you live. When did it last erupt?

What to ask your scientist

• What are the layers inside the Earth?
• Why does New Zealand have more earthquakes than Australia?
• What evidence shows that continents move?
• What happens where two plates crash into each other?

A small note on care: the hot water for one model is handled only by the teacher, and students work carefully with scissors and rubber bands.

Warm regards,

The Year 8 science team

Printed from the free seegongsik Plate Tectonics teaching pack · seegongsik.com/au/y8/earth-and-space/AC9S8U03/pack

Inside the Earth

The Earth is layered: a thin crust of cool, solid rock; a thick mantle of hot rock that is solid but creeps very slowly; a liquid outer core of iron and nickel; and a solid inner core. The crust is so thin that on a scale strip 64 cm long it is less than half a centimetre. The crust and the top of the mantle are broken into plates that ride on the creeping mantle below. Groups mark the layers on a strip at 1 cm for every 100 km, then sort twelve facts into the four layers.

We are learning to

• describe the layers of the Earth and the state of each,
• use a scale to compare the thickness of the layers,
• explain why the plates can move on the mantle.

Success criteria

• I can work out where each boundary goes on the scale strip and mark it accurately.
• I can explain how the mantle can be solid and still move.

You need

• for each group: a strip of paper at least 70 cm long (adding-machine roll or taped A4), a metre ruler and four coloured pencils,
• the worksheet (next sheet), one per student, and the layer cards (third sheet), one set per pair; a peach or a boiled egg cut in half, for the opening.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the model, the board and the strip in Session A, and the cards and Part C in Session B.

Watch for these ideas

• “The mantle is a sea of liquid lava.” It is solid rock, so hot that it creeps a few centimetres a year, like very stiff toffee.
• “The centre is liquid because it is hottest.” The inner core is the hottest part but stays solid because of the enormous pressure.
• “The crust is thick.” Compared with the whole Earth it is thinner than the skin of an apple.

Make it easier, make it bigger

• Easier: give the four boundary positions already worked out, and ask groups only to mark and colour.
• Bigger: the deepest hole ever drilled went about 12 km down. Mark it on your strip, and say what fraction of the way to the centre it reached.

Answers and look-fors

• Part A: crust (under a continent) from 0 to 35 km, 35 km thick, 0 to 0.4 cm on the strip; mantle from 35 to 2,900 km, 2,865 km thick, 0.4 to 29 cm on the strip; outer core from 2,900 to 5,150 km, 2,250 km thick, 29 to 51.5 cm on the strip; inner core from 5,150 to 6,371 km, 1,221 km thick, 51.5 to 63.7 cm on the strip.
• Part B: crust C, D, I, J; mantle A, F, G, K, L; outer core E, H; inner core B.
• Part C: 1. The mantle, 2,865 km thick. 2. It is solid, but so hot that over millions of years it slowly creeps, a few centimetres a year, carrying the plates on top. 3. On the strip the crust is 0.4 cm; the peach skin is a much larger share of the peach.
• Bigger: 12 km is 0.12 cm on the strip, about 12 ÷ 6,371 ≈ 1/531 of the way to the centre.

Inside the Earth

A. The scale strip

Scale: 1 cm on the strip stands for 100 km. The centre of the Earth is 6,371 km down, so the strip is 63.7 cm long.

B. Twelve facts

C. Questions

Which layer?

Cut out the cards. Lay down the four grey heading cards, read each fact, and sort it.

Teacher note: the piles are not the same size; the answer is on the plan.

Plates on the move

The plates move a few centimetres a year. The Australian plate moves north-north-east about 7 cm a year, about twice as fast as fingernails grow; in 2020 Australia’s official map coordinates were moved 1.8 m to catch up with 26 years of drift. Over millions of years those centimetres add up to thousands of kilometres. The plates are moved by slow currents in the hot mantle, which rises where it is hottest and sinks where it is cooler: convection. Students work out how far Australia travels and watch a model of convection.

We are learning to

• calculate how far a plate moves over different spans of time,
• describe convection and how it can move the plates,
• use a model and say what it shows and what it does not.

Success criteria

• I can convert a distance in centimetres to metres and kilometres, and show my working.
• I can draw the path of the warm water in the model and link it to the mantle.

You need

• for the demonstration: a clear tank or large jar of cold water, a small bottle with a cap, a kettle, food colouring and tongs or string to lower the bottle,
• the worksheet (next sheet), one per student, and the exit tickets (third sheet).

Safety: you fill the bottle with hot water from the kettle and lower it; students watch from their seats.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the fingernails and the calculations in Session A, and the model, the board and Part D in Session B.

Watch for these ideas

• “The continents float on the sea.” They are part of plates that ride on the mantle; the oceans sit on plates too.
• “Plates only move during earthquakes.” They creep all the time; an earthquake is the edge catching up in one jerk.
• “The mantle is boiling.” It is solid rock moving by convection, far too slowly to see.

Make it easier, make it bigger

• Easier: give the conversion steps: centimetres ÷ 100 = metres, and metres ÷ 1000 = kilometres.
• Bigger: at 7 cm a year, how many years would Australia take to move 1,000 km?

Answers and look-fors

• Part A: one year: 7 cm = 0.07 m; your lifetime so far (13 years): 91 cm = 0.91 m; from 1994 to 2020 (26 years): 182 cm = 1.82 m; since the last dinosaurs (66 million years): 462,000,000 cm = 4,620,000 m = 4,620 km.
• Part B: 7 × 26 = 182 cm ≈ 1.8 m, which matches the 1.8 m shift; without it, maps and GPS would disagree by almost two metres.
• Part C: the colour rises from the hot bottle, spreads along the top, cools and sinks at the sides, then is drawn back towards the bottom: a loop. In the mantle, hot rock rises under ridges, spreads sideways under the plates and sinks where it is cooler, dragging the plates along.
• Part D: 1. It is far too slow to feel, and everything around us moves with it. 2. About 4,620 km, about the width of Australia itself. 3. The model is water, fast and liquid; the mantle is solid rock that moves millions of times more slowly.
• Bigger: 1,000 km is 100,000,000 cm; ÷ 7 ≈ 14.3 million years.

Plates on the move

A. How far does Australia move?

The Australian plate moves about 7 cm a year. 100 cm = 1 m; 1000 m = 1 km.

B. The map moved

In 2020 the official latitude and longitude of every place in Australia were moved about 1.8 m, the drift of the 26 years since the last reset in 1994.

C. A convection model

D. Questions

Exit tickets

Cut out one ticket for each student.

Plates pulling apart

At a divergent boundary two plates move apart. Hot mantle rock rises into the gap, partly melts and cools into new crust, so the sea floor is youngest at the ridge and older the further away it is. Under the oceans this builds mid-ocean ridges, the longest mountain chains on Earth; on land it opens rift valleys, such as the East African Rift. Students graph the age of sea-floor rock against its distance from a ridge to find the spreading rate, and build a paper model of new sea floor forming.

We are learning to

• describe how new crust forms at a divergent boundary,
• name the features divergent boundaries build, under the sea and on land,
• use a graph to work out a spreading rate.

Success criteria

• I can plot the data, draw a line of best fit and work out the spreading rate with units.
• I can explain why the youngest rock is found at the ridge.

You need

• for each pair: the paper spreading model (third sheet), scissors, sticky tape and two coloured pencils,
• the worksheet (next sheet), one per student.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the board and the paper ridge in Session A, and the graph and Part C in Session B.

Watch for these ideas

• “New crust forms at every boundary.” Only at divergent boundaries; crust sinks back into the mantle at convergent ones.
• “The Earth is getting bigger.” As much crust is destroyed at subduction zones as is made at ridges.
• “Ridges are only under the sea.” Iceland sits on the Mid-Atlantic Ridge, and East Africa is splitting on land.

Make it easier, make it bigger

• Easier: draw the line of best fit together and read one value off it before students work out the rate.
• Bigger: the Atlantic is about 5,000 km wide. At the full spreading rate, how long has it taken to open?

Answers and look-fors

• Part A: the points lie close to a straight line through the origin: the further from the ridge, the older the rock.
• Part B: 200 km in 16.2 million years ≈ 12.3 km per million years, which is 12.3 mm a year on each side; both sides together about 2.5 cm a year.
• Part C: 1. At the ridge, where it has only just formed from rising mantle rock. 2. About 8.1 million years: the sea floor spreads the same way on both sides. 3. A long valley, volcanoes and earthquakes, and in time a narrow sea, like the Red Sea.
• Bigger: 5,000 km = 500,000,000 cm; ÷ 2.5 ≈ 200 million years, which matches the age of the oldest Atlantic sea floor.

Plates pulling apart

A. Rocks from the sea floor

Rock samples drilled from the sea floor on one side of a mid-ocean ridge (typical values).

B. The spreading rate

C. Questions

A paper mid-ocean ridge

Cut out the base and the two strips. Cut along the dashed slit in the base. Tape the ends of the strips together marked “start”, push them up through the slit from underneath, and pull one strip each way. Colour each pair of boxes as it comes out, in the same colour on both sides.

Teacher note: the boxes that came out first end up furthest from the slit, just as the oldest sea floor is furthest from the ridge.

Plates colliding

At a convergent boundary two plates push together. Where ocean crust meets continental crust, the denser ocean plate sinks under the continent: subduction. It leaves a deep trench offshore, and as water squeezed from the sinking plate melts the mantle above it, a line of volcanoes rises inland. Where two ocean plates meet, one sinks and a curved chain of volcanic islands forms. Where two continents meet, neither sinks, and the crust folds into the highest mountains, such as the Himalaya. Students reason about density, fold layers to make mountains, and label three collisions in cross-section.

We are learning to

• explain why ocean crust sinks under continental crust,
• describe the features formed at three kinds of convergent boundary,
• use a model of folding and say what it shows.

Success criteria

• I can use density to explain which plate sinks.
• I can label the features of all three collisions and say how each formed.

You need

• for each group: a damp hand towel, or three thin sheets of different-coloured modelling clay, and a ruler,
• the worksheet (next sheet) and the collision evidence sheet (third sheet), one each per student.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the densities, the board and the model in Session A, and the three collisions in Session B.

Watch for these ideas

• “The bigger plate wins.” The denser crust sinks, whatever the size of the plate.
• “The volcanoes are right on the trench.” Rock melts where the sinking plate is about 100 km deep, so the volcanoes rise well inland.
• “Mountains are pushed up in one go.” They rise a few millimetres a year over millions of years.

Make it easier, make it bigger

• Easier: give the seven labels as a jumbled word bank for the evidence sheet.
• Bigger: the Himalaya are still rising a few millimetres each year. Why do they not just keep growing taller forever?

Answers and look-fors

• Part A: ocean crust (3 g/cm³) is denser than continental crust (2.7 g/cm³), so the ocean plate sinks under the continent.
• Part B, example group: 50 cm became 32 cm, about 36% shorter, with folds about 7 cm high. Squeezing a layer sideways makes it shorter and thicker, rising in folds, as the crust does where continents collide.
• Evidence sheet: 1 a deep ocean trench, where the ocean plate bends down; 2 a volcano, fed by rock melting above the sinking plate; 3 mountains, where the edge of the continent is squeezed and crumpled; 4 the ocean plate, sinking into the mantle; 5 a trench, where one ocean plate dives under the other; 6 a curved chain of volcanic islands; 7 very high mountains, where neither continent sinks and the crust folds and piles up.
• Part C: 1. The ocean plate sinks; ocean and continent (A). 2. Neither sinks, because both are light continental crust, so they crumple into high mountains (C). 3. Earthquakes, volcanic eruptions and tsunamis.
• Bigger: rain, ice and rivers wear the mountains down all the time; the height is a balance between uplift and erosion.

Plates colliding

A. Which one sinks?

B. Make mountains

C. Questions

Three collisions

Each drawing shows two plates meeting, cut through from the side. Label each numbered feature.

Sliding past, sticking and slipping

At a transform boundary two plates slide past each other sideways. No crust is made or destroyed, but the rough rock along the fault catches and locks while the plates keep moving, so the rock bends and stores energy, sometimes for hundreds of years. When the fault slips, the rock snaps back and the stored energy shakes the ground: an earthquake. Students build an earthquake machine, a block dragged by a rubber band, and compare how it jerks over a smooth board and over sandpaper.

We are learning to

• describe what happens at a transform boundary,
• explain how strain builds up and is released as an earthquake,
• use a model to compare a smooth fault with a rough one.

Success criteria

• I can find the mean jump and the mean wait for each surface.
• I can use the words friction, strain and slip to explain an earthquake.

You need

• for each group: a wooden block or a brick with a hook, a thick rubber band, a smooth board, a strip of coarse sandpaper, a metre ruler, sticky tape and a stopwatch,
• the worksheet (next sheet), one per student, and the exit tickets (third sheet).

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the board and the machine in Session A, and the means, the comparison and Part C in Session B.

Watch for these ideas

• “Earthquakes happen when plates crash.” At a transform fault the plates are stuck, then slip; most quakes are sudden slips.
• “The ground opens and swallows things.” The damage comes mostly from shaking, landslides and, at sea, tsunamis.
• “An earthquake moves a plate a long way.” Even a huge one slips a few metres; it releases movement that built up over many years.

Make it easier, make it bigger

• Easier: test the sandpaper only, and compare with the example results for the smooth board.
• Bigger: in New Zealand’s 2016 Kaikoura earthquake, parts of one fault slipped about 10 m. If the plates there move about 4 cm a year, roughly how long could that strain have taken to build?

Answers and look-fors

• Part A, example group: smooth board: mean jump 0.9 cm, mean wait 1.1 s; sandpaper: mean jump 3.1 cm, mean wait 4 s.
• Part B: 1. On sandpaper the block waited longer and jumped further. 2. More friction holds the block longer, so the band stretches further and stores more energy before it slips. 3. A rough, strongly locked fault stores strain for longer and releases it in bigger, rarer earthquakes.
• Part C: 1. Transform: the two sides grind past each other sideways. 2. Strain is still building, so a large earthquake may be coming; a quiet fault is not a safe fault. 3. Build to earthquake codes, secure heavy furniture, plan what to do in a quake.
• Bigger: 10 m = 1000 cm; ÷ 4 = 250 years (a rough estimate, since some of the movement is taken up in other ways).

Sliding past, sticking and slipping

A. The earthquake machine

Example group results: five jumps on each surface.

B. Compare

C. Real faults

The Alpine Fault runs along New Zealand’s South Island. The ground on one side moves past the other at a few centimetres a year, but the fault itself has not slipped in a large earthquake for about three hundred years.

Exit tickets

Cut out one ticket for each student.

Where the ground shakes

Earthquakes and volcanoes are not scattered at random: most lie in narrow belts along plate boundaries, and around the Pacific those belts form the Ring of Fire. Australia sits near the middle of its plate, so it has fewer and smaller earthquakes, though not none, and no active volcanoes on the mainland. Students plot ten earthquakes and eight volcanoes on a map grid of our region, and use the pattern to find the edges of the Australian plate.

We are learning to

• plot positions from latitude and longitude,
• describe the pattern of earthquakes and volcanoes, and the points that do not fit,
• use the pattern as evidence for where plate boundaries are.

Success criteria

• I can plot all eighteen points accurately and draw where I think the plate boundaries run.
• I can explain why three of the earthquakes do not fit the pattern.

You need

• the worksheet (next sheet) and the map grid (third sheet), one each per student, a sharp pencil and a ruler,
• a world atlas or a wall map for checking.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the plotting in Session A, and the board, the edges and Part B in Session B.

Watch for these ideas

• “Earthquakes happen on coasts.” They happen at plate boundaries, which may be out at sea or far inland, like the Himalaya.
• “Australia never has earthquakes.” It has many small ones every year and occasional damaging ones, such as Newcastle in 1989.
• Mixing up latitude and longitude when plotting; always go across first, then up or down.

Make it easier, make it bigger

• Easier: plot the earthquakes only, then add the volcanoes as a class on the board.
• Bigger: the 2004 Sumatra earthquake sent a tsunami across the Indian Ocean as far as Africa. Explain how an earthquake under the sea can make a tsunami.

Answers and look-fors

• Map: the large earthquakes and all the volcanoes lie in a curving belt from Sumatra and Java through the Philippines and Taiwan to Japan, and a second belt from Papua New Guinea through the Solomon Islands to New Zealand: the northern and eastern edges of the Australian plate.
• Part B: 1. A narrow belt around the north and east of the map; the volcanoes follow the same belt. 2. Meckering, WA (6.5), Newcastle, NSW (5.6), Petermann Ranges, NT (6.1): they are inside the Australian plate, far from any boundary, and smaller (magnitude 5.6 to 6.5) than those on the belt (7.5 to 9.1). 3. Strain still builds inside a plate as it is pushed from its edges, and is sometimes released in a smaller earthquake.
• Part B: 4. Australia is far from a plate boundary; its youngest volcanoes, in western Victoria and south-eastern South Australia, last erupted a few thousand years ago and are not active now.
• Bigger: the quake lifted a long strip of sea floor by several metres in seconds, pushing up all the water above it; that bulge of water spread out as waves across the ocean.

Where the ground shakes

A. The data

Positions are rounded to the nearest degree. Plot each earthquake as a small cross with its magnitude beside it, and each volcano as a small triangle.

B. Questions

Our region: plot the earthquakes and volcanoes

Squares mark cities, for checking your plotting. Draw the plate boundaries you think the pattern shows, in coloured pencil.

Evidence I: a jigsaw of continents

In 1912 Alfred Wegener proposed that the continents were once joined and have since drifted apart. His evidence: the coasts of South America and Africa fit together; the same fossils of land animals and plants, which could not cross an ocean, are found on continents now far apart; and rock layers and the scratches of ancient ice sheets line up when the continents are fitted back together. Students assemble five simplified pieces of the southern supercontinent, Gondwana, and use the fossil zones to test their fit.

We are learning to

• describe the evidence Wegener used for continental drift,
• use fossil evidence to decide which continents were once joined,
• explain why most scientists did not accept the idea at first.

Success criteria

• I can assemble the puzzle so every fossil zone runs on unbroken from piece to piece.
• I can explain why a freshwater reptile is good evidence that two continents were joined.

You need

• the jigsaw pieces (third sheet), one per pair, scissors and glue or sticky tape,
• the worksheet (next sheet), one per student; a globe or a world map.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the map and the jigsaw in Session A, and the board and Part B in Session B.

Watch for these ideas

• “The animals swam across.” Mesosaurus lived in fresh water, and Lystrosaurus and Cynognathus were land animals; none could cross an ocean.
• “The continents have always had today’s shapes.” Coasts change as sea level rises and falls; the edge of the continental shelf fits even better.
• “Wegener was right about everything.” He was right that continents moved, but not about how: they move as part of plates.

Make it easier, make it bigger

• Easier: start pairs off by joining South America and Africa, the clearest fit.
• Bigger: coal, which forms from swamp plants, is found in Antarctica, and scratches from ancient ice sheets are found in Australia, India and Africa. What do these two clues add?

Answers and look-fors

• Part A: Mesosaurus: South America, Africa; Cynognathus: South America, Africa; Lystrosaurus: Africa, India, Antarctica; Glossopteris: South America, Africa, India, Antarctica, Australia.
• Part B: 1. All five: South America, Africa, India, Antarctica and Australia. 2. It lived in lakes and rivers and could not survive in, or swim across, a salty ocean, so the land must have been joined. 3. The fossil zones would be broken; joined edges are where the zones run on. 4. He could not explain what force moved whole continents; evidence from the sea floor in the 1950s and 1960s (Lesson 8) showed how.
• Part C: the five pieces fitted with each fossil zone unbroken; South America and Africa side by side, Antarctica below, India and Australia along its northern edge.
• Bigger: Antarctica was once warm enough for swamps, so it must have been nearer the equator; the ice scratches line up into one ice sheet when the continents are joined, so they were once together near the South Pole.

Evidence I: a jigsaw of continents

A. Which fossils, where?

Tick each continent where the fossil zone appears on your assembled puzzle.

B. Weigh the evidence

C. Our Gondwana

Put Gondwana back together

Cut out the five pieces along the dashed lines. Fit them together so that every coloured fossil zone runs on unbroken from one piece to the next.

Teacher note: the pieces are simplified and not to scale; real coastlines fit best at the edge of the continental shelf.

Evidence II: the sea floor remembers

In the 1950s and 1960s, ships mapping the ocean floor found what Wegener had lacked. A ridge runs down the middle of the oceans; the rock is youngest at the ridge and older away from it; and the rock records the Earth’s magnetic field, which has flipped direction many times. New rock cooling at the ridge locks in the direction of the field at that time, so matching magnetic stripes lie on both sides of the ridge, like a recording. And no open ocean floor is older than about 180 million years, while crystals from the Jack Hills in Western Australia are 4.4 billion years old: sea floor is made at ridges and destroyed at trenches.

We are learning to

• explain how magnetic stripes form on either side of a mid-ocean ridge,
• use the stripes and a spreading rate to work out widths and ages,
• explain how sea-floor evidence answered the question Wegener could not.

Success criteria

• I can complete the stripe pattern and explain why it is a mirror image.
• I can work out the width of each band from how long it lasted and the spreading rate.

You need

• the worksheet (next sheet), one per student, a dark pencil and a calculator; a compass and a bar magnet, for the opening,
• the exit tickets (third sheet).

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the compass, the board and the stripes in Session A, and Part B in Session B.

Watch for these ideas

• “The stripes are different-coloured rock.” They cannot be seen; ships measure them by towing instruments that sense magnetism.
• “The magnetic field flips every few years.” It flips at irregular times, usually hundreds of thousands of years apart.
• “The sea floor is as old as the Earth.” It is recycled: made at ridges and swallowed at trenches.

Make it easier, make it bigger

• Easier: work out the youngest band together before students do the others.
• Bigger: a ship measures the youngest band at another ridge as 32 km wide on each side. What is that ridge’s spreading rate?

Answers and look-fors

• Part A: the right-hand side is the mirror of the left: dark, white, dark, white outwards from the ridge. Widths at 20 km per million years: 0 to 0.8 million years ago (normal), 16 km; 0.8 to 2.6 million years ago (reversed), 36 km; 2.6 to 3.6 million years ago (normal), 20 km; 3.6 to 5.9 million years ago (reversed), 46 km.
• Part A: the stripes are mirrored because the ridge makes new rock on both sides at the same time, and both sides record the same field as they cool.
• Part B: 1. The sea floor is destroyed at trenches, sinking back into the mantle, so none survives for long; continental rock is too light to sink, so very old pieces remain. 2. It showed the sea floor spreading from the ridges, pushing the plates apart: the movement Wegener could not explain. 3. Twice the rate makes every band twice as wide: the youngest 32 km.
• Bigger: 32 km ÷ 0.8 million years = 40 km per million years, or about 4 cm a year on each side.

Evidence II: the sea floor remembers

A. Magnetic stripes

Dark = rock that cooled when the field pointed the way it does today (normal); white = rock that cooled when it was reversed. The sea floor spreads 20 km every million years on each side. Shade the right-hand side.

B. Old and young rocks

The oldest open ocean floor is about 180 million years old. Tiny zircon crystals from the Jack Hills in Western Australia are about 4.4 billion years old (4,400 million years), the oldest pieces of the Earth ever found.

Exit tickets

Cut out one ticket for each student.

Australia on a moving plate

Australia rides near the middle of its plate, moving north about 7 cm a year. Its northern edge pushes into the plates of Asia and the Pacific, building the trench and volcanoes of Indonesia and the mountains of New Guinea. To the south-east, New Zealand sits right on a boundary, with the Alpine Fault sliding sideways. To the south, the plate is pulling away from Antarctica along a mid-ocean ridge. Pairs sort twelve famous places by the kind of boundary that made them, then describe each edge of our own plate.

We are learning to

• identify the kind of boundary from the features it makes,
• describe the boundaries around the Australian plate,
• predict how the plate’s movement will change the region.

Success criteria

• I can sort all twelve places and give the clue that decided each one.
• I can name the kind of boundary on three edges of the Australian plate.

You need

• the place cards (third sheet), one set per pair, and the worksheet (next sheet), one per student,
• a world atlas, and the map grids from Lesson 6.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the board and the cards in Session A, and our plate and the future in Session B.

Watch for these ideas

• “Australia is not on a plate.” Every continent rides on a plate; Australia is simply far from the edge of its own.
• “A plate’s edge is the coast.” Boundaries can run far out at sea, like the ridge south of Australia.
• “Each country has one kind of boundary.” New Zealand has transform and convergent boundaries.

Make it easier, make it bigger

• Easier: give the clue words for each heading first: ridge or rift; trench, volcanoes or mountains; sliding sideways.
• Bigger: India began colliding with Asia about 50 million years ago, raising the Himalaya. Predict where a new mountain range could rise as Australia keeps moving north.

Answers and look-fors

• Part A: divergent B, F, I, J; convergent A, C, D, H, K, L; transform E, G.
• Part B: north: indonesia and new guinea, convergent: the plate sinks under Indonesia at the Java Trench, feeding volcanoes, and pushes up the New Guinea Highlands; south-east: new zealand, mostly transform along the Alpine Fault, with convergent boundaries to the north and south of it; south: between australia and antarctica, divergent: a mid-ocean ridge where the two have been spreading apart for tens of millions of years.
• Part C: 1. Convergent: the trenches, volcanoes and mountains it builds are among the largest features on Earth. 2. The Australian plate is still pushing north into the plates beside it. 3. The sea narrows and in time closes; Australia and New Guinea push into Asia.
• Bigger: along the line where the Australian plate meets Asia, through Indonesia and New Guinea, as Australia pushes into Asia.

Australia on a moving plate

A. Twelve places

B. The edges of our plate

C. Questions

Which kind of boundary made it?

Cut out the cards. Lay down the three grey heading cards, read each card, and sort it.

Teacher note: the piles are not the same size; the answer is on the plan.

Show what we know

The last lesson brings the term together. Scientists recorded earthquakes under a curved chain of volcanic islands beside a deep ocean trench, and noted how deep each one was. Students plot depth against distance from the trench, find the sloping line of quakes that traces a sinking plate, name the boundary and explain the islands. Then each student sits the final check on their own, and the class finishes with the unit quiz on the board.

We are learning to

• use earthquake data as evidence for a sinking plate,
• identify a boundary and explain its features,
• show what we know about plate tectonics on our own.

Success criteria

• My graph shows the quakes getting deeper away from the trench, and I can explain why.
• I can back each answer on the final check with a feature, a number or a reason.

You need

• the mystery boundary task (next sheet) and the final check (third sheet), one each per student, with a ruler and a calculator,
• the interactive unit open for the closing quiz.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the task and the partner check in Session A, and the final check and the class quiz in Session B.

Watch for these ideas

• Plotting depth upwards: the graph then looks like a mountain, not a sinking plate.
• Calling it a divergent boundary because there are volcanoes; the trench and the deepening quakes show a plate sinking.
• Placing the volcanoes on the trench; they rise where the sinking plate is about 100 km down.

Make it easier, make it bigger

• Easier: plot the first two points together and describe the pattern as a class before students go on.
• Bigger: use the graph to estimate the angle at which the plate sinks.

Answers and marking guide

• Task: 1. The quakes get steadily deeper away from the trench, from about 15 km at the trench to 205 km at 250 km away, along a sloping line. 2. They happen in the sinking plate as it slides down into the mantle, so they trace its slope. 3. Convergent: one ocean plate sinking beneath another. 4. Where the plate is about 100 km down, about 115 km from the trench: water from the plate melts the mantle above it. 5. Earthquakes, tsunamis and eruptions; for example, warning systems, evacuation plans and strong buildings.
• Check: 1. divergent boundary. 2. Crust (thin, solid rock), mantle (hot solid rock that creeps), outer core (liquid iron and nickel), inner core (solid iron and nickel). 3. the same freshwater reptile fossils on both. 4. New crust forms at the ridge from rising mantle rock and moves away on both sides, so rock gets older away from it.
• Check: 5. two continents collide. 6. The rough rock along the fault locks while the plates keep moving, so it bends and stores energy; when it slips, the rock snaps back and the energy shakes the ground. 7. 5 × 2,000,000 = 10,000,000 cm = 100 km. 8. Australia is near the middle of its plate, far from a boundary; New Zealand sits on the boundary, where the plates grind and sink.
• Bigger: the line drops about 190 km over 250 km, an angle of about 37° on a scale drawing.
• Scoring: 1 mark each for 1, 3 and 5; 2 marks each for 2, 4, 6, 7 and 8. The rubric near the front of the pack turns the task and the check into a level.

The mystery boundary

A curved chain of volcanic islands lies beside a deep ocean trench. Scientists recorded how deep earthquakes were at different distances from the trench.

Show what we know

Show what you know about plate tectonics. Read each item, then circle or write.

Teacher note: the marking guide is on this lesson’s plan; the rubric near the front of the pack turns the score into a level.