The Rock Cycle: 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 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: rock is never made once and left alone. It is weathered, carried, laid down, buried, baked, melted and cooled again, in a cycle with no fixed path, on timescales from days to hundreds of millions of years. How a rock formed shows in its texture, and gives it the properties that decide how we use it.

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. Look ahead: a rock kit helps in Lessons 1 and 8, and the rock pieces for Lesson 8 should be dried the day before.

Safety and care in one look

Eye protection goes on whenever vinegar is used. Jar lids are screwed on firmly before shaking, the hot Epsom salt solution is made and poured by the teacher, and steel nails are used for scratching away from hands. Nothing is tasted, including the crystals.

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 introduce the three families and the cycle that links them. Lessons 3 to 6 follow the cycle round: weathering and erosion, sediment becoming rock, magma cooling into crystals, and rock remade by heat and pressure. Lesson 7 puts the processes on a timescale, Lesson 8 links properties to uses, Lesson 9 reads Australia’s landscapes, and Lesson 10 brings it together.

Curriculum links (Australian Curriculum V9)

The whole term teaches the Science Understanding descriptor AC9S8U04 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 road cutting task, plus the “Show what we know” check.

Materials for the whole term

One gathering session covers all ten lessons. A rock kit from the prep room makes Lessons 1 and 8 easier; the rest comes from the kitchen, the garden and a hardware store. Two things are worth doing ahead: dry the rock pieces for Lesson 8 the day before, and chill one slide per group for Lesson 5.

The one-trip list

• From the prep room: a rock kit, hand lenses, balances, glass slides, droppers, timers and eye protection.
• From the supermarket: white vinegar, Epsom salts, uncooked rice, PVA glue and chalk.
• From home or the garden: gravel, sand, garden soil, a river pebble, plastic jars with lids and tall clear jars.
• From a hardware store or the school: steel nails, plasticine, paper cups, A3 paper and a kettle.

Safety and care in one look

• Eye protection whenever vinegar is used; rinse spills with water.
• Jar lids screwed on firmly before shaking; chalk dust wiped up with a damp cloth.
• The hot Epsom salt solution is made and poured by the teacher; nothing is tasted.
• Steel nails are used for scratching away from hands, on a bench.

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 road cutting task, in which students name six rocks and work out the order of the events that made them, 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: igneous rock, sedimentary rock and metamorphic rock in Lesson 1; rock cycle, weathering, erosion and magma in Lesson 2; abrasion in Lesson 3; sediment, compaction, cementation and fossil in Lesson 4; crystal, intrusive and extrusive in Lesson 5; parent rock in Lesson 6; porous and durable in Lesson 8.

Dear families

This term in science, Year 8 studies the rock cycle: how rocks are broken down, carried away, laid down, buried, baked and melted, and made again, over timescales from days to hundreds of millions of years. Students learn to read a rock’s story from its texture, and why different rocks suit different jobs.

Along the way your student will identify rocks with a key, shake chalk in a jar to see how rivers round off pebbles, grow crystals to see why granite and basalt look so different, squeeze rice in plasticine to model how slate forms, and read the story of a road cutting.

Try this at home

• Look at the stone around your home or street: benches, steps, walls, kerbs. Can you tell which family each rock belongs to?
• Find a rounded pebble and a sharp chip of rock. What happened to the pebble that did not happen to the chip?
• Drip a little vinegar on a piece of chalk or a shell. What do you see, and what does it tell you about limestone?
• Visit an old cemetery or church, and compare how worn the marble and granite stones are.

What to ask your scientist

• What are the three families of rock, and how does each form?
• Why does granite have big crystals and basalt tiny ones?
• How can a sandstone become a magma one day?
• Why is slate good for roofs?

A small note on care: students wear eye protection when using vinegar, the teacher handles any hot water, and nothing in the science room is tasted.

Warm regards,

The Year 8 science team

Printed from the free seegongsik Rock Cycle teaching pack · seegongsik.com/au/y8/earth-and-space/AC9S8U04/pack

Reading rocks

Every rock belongs to one of three families, named for how it formed. Igneous rock cools from molten magma or lava, so its crystals interlock, or gas leaves it full of holes. Sedimentary rock is made of grains, pebbles or shells laid down in layers and cemented together. Metamorphic rock is older rock remade by heat and pressure, so it is often banded, splits into sheets or sparkles with new crystals. A rock’s texture is the clue to its story. Pairs observe eight rocks and use a key to name each one and its family.

We are learning to

• observe the texture, grain size and other properties of rocks,
• use a key to identify rocks,
• link the texture of a rock to the way it formed.

Success criteria

• I can name all eight rocks with the key and sort them into the three families.
• I can give the clue in a rock’s texture that shows how it formed.

You need

• for each pair: a class rock kit labelled A to H, or the rock cards (third sheet); a hand lens, a dropper of vinegar, a steel nail and a cup of water,
• the worksheet (next sheet), one per student.

Safety: wear eye protection with the vinegar, and wipe the rocks dry before they go back in the kit.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening, the board and four rocks in Session A, and four rocks and Part B in Session B.

Watch for these ideas

• “Shiny rocks are metamorphic.” Granite sparkles too; the question is how the crystals formed.
• “Igneous rocks are always dark.” Granite and pumice are pale; colour comes from the minerals.
• “A rock’s family is its colour or hardness.” The family is about how it formed, read from its texture.

Make it easier, make it bigger

• Easier: give each pair three rocks, one from each family, before the full set.
• Bigger: write one more question for the key that would separate marble from limestone without using vinegar.

Answers and look-fors

• Part A: A sandstone (sedimentary), B granite (igneous), C slate (metamorphic), D limestone (sedimentary), E pumice (igneous), F marble (metamorphic), G conglomerate (sedimentary), H basalt (igneous).
• Part B: igneous B, E, H; sedimentary A, D, G; metamorphic C, F.
• Part B questions: 1. Interlocking crystals (from molten rock cooling) or gas holes. 2. Grains, pebbles or shells cemented together, often in layers. 3. Bands, thin sheets, or crystals that grew in an older rock under heat and pressure. 4. Pumice: gas bubbles trapped as lava cooled very fast leave holes full of air, so it is less dense than water.
• Bigger: for example, “Can you see shells or fossils?” (limestone often has them; marble does not), or “Does it sparkle with interlocking crystals?”

Reading rocks

The key

1. Does it fizz in vinegar? Yes: go to 2. No: go to 3.
2. Shells, or tiny grains you cannot see separately: limestone. Sparkling crystals that interlock: marble.
3. Full of tiny holes, and light enough to float? Yes: pumice. No: go to 4.
4. Grains or pebbles cemented together, which rub off? Yes: go to 5. No: go to 6.
5. Rounded pebbles bigger than a pea: conglomerate. Sand grains: sandstone.
6. Large interlocking crystals of several colours? Yes: granite. No: go to 7.
7. Splits into thin, flat sheets: slate. Dark, heavy, with crystals too small to see: basalt.

A. Eight rocks

B. Three families

Eight rocks to identify

Use these cards if your class has no rock kit. Each card says what you would see and find. Use the key to name each rock.

Teacher note: the names are on the plan; the cards describe the rocks without naming them.

The rock cycle

Rock is never made once and left alone. At the surface, weathering and erosion break any rock into sediment, which is laid down and cemented into sedimentary rock. Buried deep, any rock can be changed by heat and pressure into metamorphic rock, or melted into magma, which cools into igneous rock. There is no single path: rock can take many routes round the cycle, over millions of years. Pairs build the cycle from five stage cards and eight process cards, then trace three journeys.

We are learning to

• describe the processes of the rock cycle,
• explain how any rock can become any other kind,
• say which processes happen at the surface and which happen deep underground.

Success criteria

• My cycle has every process card on the right arrow.
• I can trace a journey from one rock to another and name every process on the way.

You need

• the cycle cards (third sheet), one set per pair, an A3 sheet, glue and a pencil for arrows,
• the worksheet (next sheet), one per student.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the board and the cycle in Session A, and the journeys and Part C in Session B.

Watch for these ideas

• “Rocks go round in one fixed order.” Any rock can be weathered, changed or melted, depending on where it ends up.
• “Metamorphic rock is melted rock.” It changes while solid; once it melts, it becomes magma and then igneous rock.
• “The cycle happens quickly.” A full trip usually takes many millions of years.

Make it easier, make it bigger

• Easier: give the stage cards already placed in a ring, and ask pairs only to place the processes.
• Bigger: add an “uplift” arrow to your cycle. Where must it go for a metamorphic rock formed deep underground to be weathered?

Answers and look-fors

• Stage cards: A magma, B igneous rock, C sediment, D sedimentary rock, E metamorphic rock. Process cards: F heat and pressure, sedimentary rock to metamorphic rock; G weathering and erosion, metamorphic rock to sediment; H cooling and crystallising, magma to igneous rock; I weathering and erosion, sedimentary rock to sediment; J melting, metamorphic rock to magma; K deposition, compaction and cementation, sediment to sedimentary rock; L heat and pressure, igneous rock to metamorphic rock; M weathering and erosion, igneous rock to sediment.
• Part B: 1. granite (igneous) → weathering and erosion → sediment → deposition, compaction and cementation → sandstone (sedimentary); 2. limestone (sedimentary) → heat and pressure → marble (metamorphic) → melting → magma; 3. basalt (igneous) → buried → heat and pressure → metamorphic rock.
• Part C: 1. Rock is used again and again; there is no end point. 2. Yes: igneous rock can melt back into magma and cool again. 3. At the surface: weathering, erosion and deposition; deep underground: compaction and cementation, heat and pressure, melting. 4. The Sun drives the weather that wears rock away; the Earth’s inner heat melts and bakes rock deep down.
• Bigger: from metamorphic rock (and from igneous and sedimentary rock buried deep) up to the surface, before weathering and erosion.

The rock cycle

A. Our cycle

B. Three journeys

C. Questions

Build the rock cycle

Cut out the cards. Place the five stage cards, draw an arrow for each change, and lay each process card on its arrow.

Stage cards

Process cards

Teacher note: three cards say weathering and erosion and two say heat and pressure, because more than one kind of rock can take that path.

Breaking rock down

Weathering breaks rock down where it is. Physical weathering cracks rock as water freezes in its joints, as it heats and cools, or as roots grow into its cracks; chemical weathering dissolves it, as slightly acidic rain does to limestone. Erosion then carries the pieces away by water, wind, ice and gravity, and they round off as they knock together. Students shake chalk with gravel in a jar to model abrasion in a river, track the mass lost each minute, and drip vinegar on chalk and on granite to compare chemical weathering.

We are learning to

• tell weathering from erosion, and physical weathering from chemical,
• model abrasion and graph the results,
• explain why some rocks weather faster than others.

Success criteria

• I can work out the mean mass lost after each minute and draw the graph.
• I can explain why the chalk wore more slowly as the test went on.

You need

• for each group: a plastic jar with a screw lid, four pieces of chalk (about 20 g), a handful of gravel, a balance, a timer, a dropper of vinegar and a piece of granite,
• the worksheet (next sheet), one per student, and the exit tickets (third sheet).

Safety: screw the lid on firmly before shaking, wear eye protection with the vinegar, and wipe up chalk dust with a damp cloth.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the pebble, the board and the jar in Session A, and the vinegar, the graph and Part D in Session B.

Watch for these ideas

• “Weathering and erosion are the same.” Weathering breaks rock where it is; erosion carries the pieces away.
• “Rocks are too hard to wear away.” Over thousands of years even granite crumbles.
• “Acid rain is the only chemical weathering.” Ordinary rain is slightly acidic too, and slowly dissolves limestone.

Make it easier, make it bigger

• Easier: weigh the chalk only at the start and after four minutes, and compare.
• Bigger: plan a test of whether water in the jar would make the chalk wear faster. What would you keep the same?

Answers and look-fors

• Part A, example class means: 0 min 20.0 g, 1 min 18.6 g, 2 min 17.4 g, 3 min 16.3 g, 4 min 15.4 g; mass lost 0.0, 1.4, 2.6, 3.7, 4.6 g.
• Part B: a curve that rises steeply at first and then less steeply; the losses each minute were 1.4, 1.2, 1.1, 0.9 g.
• Part C: the chalk fizzes as the vinegar reacts with it and a little dissolves; the granite does not change.
• Part D: 1. About 4.6 g, about 23% of the chalk. 2. The sharp corners broke off first; as the pieces rounded, there was less to chip away. 3. Pebbles knock against each other and the riverbed, wearing off their corners. 4. Limestone and marble react with the slightly acidic rain and slowly dissolve; granite does not.
• Bigger: the same chalk, gravel, jar, shaking speed and time; only add the water.

Breaking rock down

A. Chalk in a jar (mass in g, example class)

B. Graph

C. Vinegar test

D. Questions

Exit tickets

Cut out one ticket for each student.

Layer upon layer

Sediment settles where moving water slows, the biggest and heaviest grains first. Layer builds on layer; the weight above squeezes out the water (compaction), and minerals dissolved in the water glue the grains together (cementation), making sedimentary rock. Fossils are found almost only in sedimentary rock, and the layers read like the pages of a book, the oldest at the bottom. Students settle mixed sediment in a jar of water and measure the layers, cement sand into a model rock, and read the layers of a sea cliff.

We are learning to

• describe how sediment settles in layers and becomes rock,
• explain why the oldest layers are at the bottom,
• read the story of past environments in a cliff.

Success criteria

• I can explain the order of the layers in the jar using the size of the grains.
• I can put the cliff’s layers in order and say what each one tells us.

You need

• for each group: a tall clear jar with a lid, a cup each of gravel, sand and garden soil, water, a ruler; for the model rock, a paper cup, a spoon of PVA glue and some dry sand,
• the worksheet (next sheet) and the cliff evidence sheet (third sheet), one each per student.

Set up the jars at the start of the lesson; the finest mud keeps the water cloudy for hours, so look again the next day.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the jar, the board and the model rock in Session A, and the layers and the cliff in Session B.

Watch for these ideas

• “The heaviest layer is the oldest because it is heaviest.” The bottom layer is oldest because it was laid down first.
• “Sediment turns to rock in a year or two.” Compaction and cementation take thousands to millions of years.
• “Fossils are found in every kind of rock.” Melting or strong heat destroys them, so they are almost always in sedimentary rock.

Make it easier, make it bigger

• Easier: give the layer names in a jumbled list for students to put in order from the bottom.
• Bigger: a cliff has a layer of tilted beds below flat ones. What must have happened between the two?

Answers and look-fors

• Part A, example group, from the bottom: gravel 14 mm, coarse sand 18 mm, fine sand 11 mm, silt 7 mm, clay 4 mm; total 54 mm. The biggest, heaviest grains sink fastest, so they settle first, at the bottom; the clay settles last and slowest.
• Part B: pressing the sand stands for compaction by the weight of layers above; the glue stands for cementation by minerals in the water.
• Cliff: 1. Layer 1 is oldest and layer 5 youngest: each was laid on the one below. 2. A sea, because shells are made by sea creatures. 3. Fast water, such as a river in flood, carried the large pebbles. 4. From sandy, to quiet muddy water, to sea, to a fast river, to sandy again. 5. The plants and animals were buried in sediment before they rotted, and the rock was never melted.
• Bigger: the lower layers were tilted by earth movements and worn flat, before new flat layers were laid on top.

Layer upon layer

A. The settled jar

B. A model rock

C. Questions

Reading a sea cliff

This cliff shows five flat layers of sedimentary rock, numbered from the bottom.

Cooling and crystals

Igneous rock forms when magma or lava cools and its minerals crystallise. The slower it cools, the longer the crystals have to grow. Granite, which cooled slowly deep underground, has large crystals; basalt, from lava that cooled quickly at the surface, has tiny ones; and lava chilled almost instantly forms glassy obsidian, or pumice if it is full of gas bubbles. Students grow crystals from a warm Epsom salt solution on a cold slide and on a warm one and measure them, as a model of fast and slow cooling.

We are learning to

• explain how the rate of cooling controls crystal size,
• use a model and compare it with real igneous rocks,
• tell where an igneous rock cooled from the size of its crystals.

Success criteria

• I can compare the mean crystal sizes and say how many times bigger the slow-cooled ones were.
• I can explain why granite has bigger crystals than basalt.

You need

• for each group: two glass slides (one chilled in a freezer or on ice, one warmed on a tile over hot water), a dropper, a hand lens and a ruler; samples of granite and basalt,
• a jar of saturated Epsom salt solution made with hot water from a kettle (you make and pour it); the worksheet (next sheet) and the exit tickets (third sheet).

Safety: you handle the hot solution; students use droppers and never taste the crystals.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the two rocks and the crystals in Session A, and the board and the comparison in Session B.

Watch for these ideas

• “Big crystals mean hotter magma.” Big crystals mean slower cooling, which gives the crystals time to grow.
• “All volcanic rock is the same.” Lava can give basalt, glassy obsidian or bubbly pumice, depending on how it cooled.
• “Our crystals are rock.” Epsom salt crystals model the idea; real magma is molten rock at over 700 °C.

Make it easier, make it bigger

• Easier: compare the two slides by eye with the hand lens, before measuring.
• Bigger: some granite has a few large crystals scattered among small ones. Suggest a cooling history that could make this.

Answers and look-fors

• Part A, example group: means cold slide (cooled fast) 0.5 mm, warm slide (cooled slowly) 2.1 mm; the slow-cooled crystals were about 4.2 times as long.
• Part B: many small, crowded crystals on the cold slide; fewer, larger, well-shaped crystals on the warm slide.
• Part C: granite cooled slowly underground (intrusive), large crystals; basalt cooled quickly at the surface (extrusive), tiny crystals; obsidian cooled almost instantly, no crystals.
• Part D: 1. The warm slide cooled slowly, giving the crystals more time to grow. 2. Granite cooled slowly deep underground; basalt cooled quickly at the surface. 3. It cooled very fast at the surface, so its crystals are too small to see.
• Bigger: the magma cooled slowly underground at first, growing a few large crystals, then rose and cooled quickly, so the rest formed small crystals.

Cooling and crystals

A. Crystal lengths (mm, example group)

B. What we saw

C. Three igneous rocks

D. Questions

Exit tickets

Cut out one ticket for each student.

Changed by heat and pressure

Metamorphic rock is rock changed by heat and pressure without melting. Deep in the crust, or beside a hot body of magma, the minerals recrystallise, and under pressure they line up across the direction of the squeeze, giving the flat sheets of slate or the light and dark bands of gneiss. Each metamorphic rock has a parent rock: shale becomes slate, limestone becomes marble, sandstone becomes quartzite and granite becomes gneiss. Students squeeze plasticine with grains of rice to watch the grains line up, and match parent rocks to the rocks they become.

We are learning to

• describe how heat and pressure change a rock without melting it,
• explain the sheets and bands in metamorphic rock,
• match parent rocks to the metamorphic rocks they become.

Success criteria

• I can use the model results to explain why slate splits into flat sheets.
• I can match four parent rocks to their metamorphic rocks and say what changed.

You need

• for each group: a ball of plasticine, 20 grains of uncooked rice, a heavy book, a plastic knife; samples of shale and slate, limestone and marble if you have them,
• the worksheet (next sheet), one per student, and the rock cards (third sheet), one set per pair.

Lesson flow (about 60 minutes)

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

Watch for these ideas

• “Metamorphic rock was melted.” It changed while solid; melted rock becomes magma and then igneous rock.
• “Pressure squashes the minerals flat.” The minerals regrow and turn so that they lie across the squeeze.
• “Any rock can become any metamorphic rock.” Which rock forms depends on the parent rock and on how hot and deep it got.

Make it easier, make it bigger

• Easier: show shale and slate side by side before the cards.
• Bigger: slate can change again, deeper and hotter, into schist and then gneiss. What would you expect to happen to the size of its crystals?

Answers and look-fors

• Part A, example group: 4 of 20 grains (20%) lay flat before squeezing and 16 of 20 (80%) after: the grains turned to lie across the direction of the squeeze.
• Part B: A shale with H slate: clay minerals line up under pressure, so it splits into thin sheets; B limestone with G marble: its calcite grains recrystallise into larger, interlocking crystals; C sandstone with E quartzite: its quartz grains grow into each other and lock tight, without melting, making a very hard rock; D granite with F gneiss: its minerals separate into light and dark bands.
• Part C: 1. Its minerals all lie in the same direction, so it breaks easily along them into flat sheets. 2. Metamorphic rock changes while solid; igneous rock forms when molten rock cools. 3. Heat from deep burial or from nearby magma; pressure from the weight of rock above and from plates pushing together.
• Bigger: the crystals grow bigger at each step, until the minerals separate into visible light and dark bands.

Changed by heat and pressure

A. Squeeze the rice

B. Parents and children

C. Questions

Which rock does it become?

Cut out the cards. Match each parent rock to the metamorphic rock it becomes under heat and pressure.

Parent rocks

Metamorphic rocks

Teacher note: the metamorphic cards are printed in a different order from their parents; the pairs are on the plan.

How long does it take?

The rock cycle runs on very different clocks. A thin lava flow crusts over in hours and cools in days; weathering can be measured in a lifetime; turning sediment into rock, or cooling a large body of magma, takes thousands to millions of years; and a whole trip round the cycle can take hundreds of millions. To compare times so different we use a time line where each mark is ten times the one before. Students work out how fast marble and granite headstones wear from a cemetery survey, then place rock cycle processes on a powers-of-ten time line.

We are learning to

• describe the timescales of rock cycle processes,
• calculate a rate of weathering from data,
• use a time line in powers of ten to compare very different times.

Success criteria

• I can plot both kinds of headstone and work out how fast each wears.
• I can place five processes on the time line and explain why we use powers of ten.

You need

• the worksheet (next sheet) and the time line sheet (third sheet), one each per student, with a ruler and a calculator,
• photos of old headstones, or a visit to a local cemetery if your school can arrange one.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the headstones and the survey in Session A, and the board and the time line in Session B.

Watch for these ideas

• “Rocks never change.” They change all the time, but mostly too slowly to notice in a lifetime.
• “Each mark on the time line adds the same amount.” Each mark multiplies by ten: 1, 10, 100, 1000 years.
• “Weathering is always slow.” Marble in rain wears measurably in a lifetime, and a cliff can collapse in a day.

Make it easier, make it bigger

• Easier: plot the marble headstones only, and read the rate from two points.
• Bigger: at the marble rate, how long would it take to wear away a 3 cm deep carving completely?

Answers and look-fors

• Part A: marble rises steadily with age, almost a straight line; granite stays close to zero.
• Part B: marble about 2 mm a century (50 years for each millimetre); granite about 0.2 mm a century, about 13 times slower.
• Part C: 1. Marble is calcite, which reacts with the slightly acidic rain and dissolves; granite’s minerals hardly react. 2. Yes, but only just: about a millimetre in a lifetime of marble; less than you could see in granite.
• Time line: A at 0.01 years, B at 50 years, C at 10,000 years, D at 1,000,000 years, E at 500,000,000 years. Powers of ten fit days and hundreds of millions of years on one page; on an ordinary line, everything but the slowest process would be squashed into the first millimetre.
• Time line questions: 1. 500,000,000 ÷ 0.01 = 50,000,000,000 times. 2. Each mark multiplies by ten, so very short and very long times both fit and can be compared. 3. The lava flow and the headstone. 4. Most of its processes take far longer than a human life.
• Bigger: 30 mm ÷ 2 mm a century ≈ 1500 years.

How long does it take?

A. A cemetery survey

How much of the carved writing had worn away (mm), on headstones of different ages (example survey).

Plot both rocks on the same axes, with a key.

B. How fast?

C. Questions

The rock cycle in powers of ten

Mark each process on the time line with its letter, then answer the questions.

The right rock for the job

The way a rock formed gives it its properties, and its properties decide what it is good for. Interlocking crystals make granite hard and almost watertight; slate’s lined-up minerals let it split into thin waterproof sheets; marble’s even crystals carve and polish well; sandstone’s cemented grains cut easily but leave spaces that soak up water. Students test rocks for how much water they soak up and how easily they scratch, then choose the best rock for six jobs.

We are learning to

• test and compare the properties of rocks,
• explain how a rock’s properties come from the way it formed,
• choose a rock for a job and justify the choice.

Success criteria

• I can work out the percentage of water a rock soaks up.
• For each job, I can name the best rock and the property that makes it best.

You need

• for each group: small dry pieces of the six rocks, a balance, a cup of water, paper towel, a steel nail and a timer,
• the worksheet (next sheet), one per student, and the exit tickets (third sheet).

Dry the rock pieces in a sunny spot the day before, so the water test starts from dry.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Start the soaking in Session A and weigh at the start of Session B, then do the jobs.

Watch for these ideas

• “Heavy rocks are strong.” Strength and hardness depend on how the grains or crystals are held together, not on mass alone.
• “Rocks do not soak up water.” Many sedimentary rocks have spaces between their grains that hold water.
• “One rock is best for everything.” Each job needs a different property, and cost and looks matter too.

Make it easier, make it bigger

• Easier: use the example values only, and choose rocks for three of the jobs.
• Bigger: in places with freezing winters, why is a porous stone a poor choice for steps? (Think about water in the pores.)

Answers and look-fors

• Part A: water soaked up = (wet mass − dry mass) ÷ dry mass × 100; the example values range from 0.2% (slate) to 6% (sandstone).
• Part B: a kitchen bench, granite: hard and soaks up almost no water, so it resists scratches and stains; roof tiles, slate: splits into thin, flat sheets that soak up almost no water; a statue, marble: even crystals and soft enough to carve fine detail, and it takes a polish; crushed rock under a road, basalt: hard, tough and heavy, so it does not wear down under traffic; garden paving and walls, sandstone: easy to cut into flat blocks, though it soaks up water and wears; making cement, limestone: it is calcium carbonate, which is heated to make the lime in cement.
• Part C: 1. Granite cooled slowly, so its crystals grew and interlocked tightly, leaving almost no spaces; sandstone is grains cemented together, with spaces between them. 2. Marble scratches easily, and acids in food such as lemon juice and vinegar dissolve its surface. 3. Sandstone soaks up rain, and the cement between its grains slowly weathers, so carvings wear and need repair.
• Bigger: water in the pores freezes and expands, cracking the stone from the inside a little more each winter.

The right rock for the job

A. Testing the rocks

Water soaked up (%) = (wet mass − dry mass) ÷ dry mass × 100.

B. Six jobs

C. Questions

Exit tickets

Cut out one ticket for each student.

Australia’s rock stories

Australia’s landscapes record the rock cycle. Uluru and Kata Tjuta are sedimentary rocks laid down about 550 million years ago, then tilted and slowly worn into the shapes we see; Wave Rock and Karlu Karlu are granite that cooled deep underground and now lies exposed and weathering; the Twelve Apostles are limestone stacks being cut by the Southern Ocean. Many of these places are sacred to their Traditional Owners, who share some of their knowledge with visitors. Pairs sort twelve Australian rocks and landmarks into the three families, then tell one landmark’s story through the rock cycle.

We are learning to

• identify the rock family of Australian landmarks from clues,
• describe a landmark’s history using the processes of the rock cycle,
• respect the cultural significance of places to their Traditional Owners.

Success criteria

• I can sort the twelve cards and give the clue that decided each one.
• I can tell one landmark’s story in at least three rock cycle steps, with a timescale.

You need

• the place cards (third sheet), one set per pair, and the worksheet (next sheet), one per student,
• a map of Australia, and photos of some of the landmarks shared by their parks or custodians.

Lesson flow (about 60 minutes)

Running two half-sessions instead? Do the opening and the cards in Session A, and the board and the stories in Session B.

Watch for these ideas

• “Uluru is one giant boulder dropped there.” It is the top of a huge layer of sandstone that continues far underground.
• “Landmarks are finished.” Every one is still weathering; at the Twelve Apostles a stack collapsed in 2005.
• “Red means igneous.” Uluru’s red colour is iron rusting on the surface of sandstone.

Make it easier, make it bigger

• Easier: underline the clue word in each card together for the first three.
• Bigger: find out which landmark near your school is made of rock, and add its own card to the sort.

Answers and look-fors

• Part A: sedimentary B, D, F, G, I; igneous A, E, K, L; metamorphic C, H, J.
• Part B, Uluru at standard: sand worn from ancient mountains was laid down in layers about 550 million years ago; buried, it was compacted and cemented into sandstone; earth movements tilted the layers almost on end; over hundreds of millions of years the softer rock around it wore away, and weathering is still shaping it.
• Part C: 1. The layers were laid down flat, then tilted by earth movements long afterwards. 2. Water seeps along the cracks, weathering the corners fastest, so the blocks round off into boulders. 3. The Twelve Apostles: waves cut the soft limestone quickly enough that stacks fall within a lifetime.
• Bigger: answers depend on the place; the card should give a clue to its family.

Australia’s rock stories

A. Twelve places

B. One rock’s story

C. Questions

Which family of rock?

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 in a road cutting that shows all three families of rock. Students name the six rocks, back each with evidence from its texture, and put the events that made the cutting in order: layers laid down, magma pushing up and baking the rock beside it, the land worn flat, and lava flowing over the top. 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

• identify rocks and their families from evidence,
• work out the order of events from the way rocks lie and cut across each other,
• show what we know about the rock cycle on our own.

Success criteria

• I can put the six events in order and give a reason for each step.
• I can back each answer on the final check with a property, a process or a number.

You need

• the road cutting task (next sheet) and the final check (third sheet), one each per student, 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

• Putting the granite first because it is at the bottom; it cuts through the layers, so it came after them.
• Calling E an igneous rock; it is limestone baked by the granite’s heat, which makes it metamorphic.
• Missing the worn surface: the wavy line shows a long gap, when rock was worn away before the lava came.

Make it easier, make it bigger

• Easier: give the rock names for A to F, and ask students to add the family and the evidence.
• Bigger: the basalt is 2 million years old and the sandstone 300 million. What can you say about the age of the granite?

Answers and marking guide

• Task A: A sandstone (sedimentary); B shale (sedimentary); C limestone with shell fossils (sedimentary); D granite (igneous); E marble, in a baked zone beside the granite (metamorphic); F basalt (igneous).
• Task B: P = 4, Q = 1, R = 6, S = 2, T = 5, U = 3; that is, 1. Sand settles and becomes sandstone (A); 2. Mud settles on top and becomes shale (B); 3. Shells and lime mud settle and become limestone (C); 4. Magma pushes up through A, B and C and cools slowly into granite (D), baking the rock around it, so the limestone beside it becomes marble (E); 5. The land is uplifted and the top is worn flat; 6. Lava flows over the worn surface and cools quickly into basalt (F).
• Task C: 1. Only rock right beside the hot granite got hot enough to change. The band runs through A and B too (baked sandstone becomes quartzite), but only the limestone becomes marble. 2. The granite cooled slowly underground (large crystals); the basalt cooled quickly at the surface (tiny crystals). 3. The granite: it cuts through the limestone, so the limestone was already there. 4. The land was raised and worn flat for a long time before the lava flowed over it; the line cuts across the granite too, so the granite came before the wearing down.
• Check: 1. igneous. 2. Compaction, as the weight of layers above squeezes out water; cementation, as minerals in the water glue the grains. 3. granite, with large crystals. 4. Heat and pressure, without melting, recrystallise its calcite into larger interlocking crystals; it becomes harder to split and loses its fossils.
• Check: 5. at the bottom. 6. 1.5 mm in 75 years is 50 years a millimetre, so 4 mm takes 200 years. 7. Slate: pressure lined up its minerals, so it splits into thin, flat sheets that soak up almost no water. 8. For example: granite weathers into sand, the sand becomes sandstone, which is baked into quartzite, which could melt into magma and cool into a new igneous rock.
• Bigger: younger than the sandstone it cuts through (300 million years) and older than the basalt that lies over it (2 million years).
• 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 road cutting

A new road was cut through a hill, showing the rocks below. Read the cutting.

Clues: A has rounded sand grains; B is fine grained and splits into thin layers; C has shell fossils and fizzes in vinegar; D has large interlocking crystals; E sparkles, fizzes in vinegar and has no fossils; F is dark, with crystals too small to see. The band around D is rock baked by the granite’s heat; where it crosses C, it is E.

A. The rocks

B. What happened, in order

Number the events 1 (first) to 6 (last).

C. Explain

Show what we know

Show what you know about the rock cycle. 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.