Ausgeology. Years 3 to 10 lessons

Year 5 Science · AC9S5U02

Shaping the land.

Mountains wear down. Rivers carry the pieces away and drop them somewhere else. Cliffs fall and beaches grow. The ground under your feet is being made and unmade all the time, mostly so slowly that you would never notice, and sometimes so fast that it makes the news.

Illustration
One landscape, four jobs. Rock breaks up in the mountains, the river carries the pieces, the pieces are dropped on the plain and at the coast, and the sea is cutting away the cliff. Can you find all four?
Weatheringrock breaks up where it is
Erosionthe pieces are picked up and moved
Transportationwater, wind or ice carries them along
Depositionthe pieces are dropped somewhere new

What we are learning

How rock breaks up, how the pieces travel, where they end up, and why some of these changes take millions of years while others take seconds.

I can

  • 1explain how weathering breaks rock into pieces without moving them.
  • 2explain how water and wind move the pieces, and what makes them move more.
  • 3explain why slowing water drops pebbles, sand and mud, and where that builds new land.
  • 4sort changes to Earth’s surface into slow and rapid, with a real example of each.
  • 5plan a fair test about erosion: one thing changed, one thing measured, everything else kept the same.

Australian Curriculum v9, AC9S5U02: “describe how weathering, erosion, transportation and deposition cause slow or rapid change to Earth’s surface”

Printable activity

Plan a fair test

A planning sheet and a results table for a real stream table: what you will change, measure and keep the same, three runs, and what you found out. The same links are at the end of the lesson.

Activity sheet (PDF) Editable (Word)

How this lesson works

  1. Look. Weather a boulder with heat, ice, wind and roots, and watch it break up.
  2. Test. Run a stream table. Change one thing at a time and measure how much soil washes away. That is a fair test.
  3. Explain. See where a river drops its load, and learn the four words scientists use.
  4. Apply. Sort real changes into slow and rapid, see how people speed erosion up or slow it down, and follow salt water into a Kakadu wetland.
  5. Show what you know. Plan your own fair test and answer five questions.

Your answers and notes are saved in this browser, so you can stop and come back.

1Look

Breaking up.

A boulder sits on a hillside. Nothing seems to happen to it. Come back in a thousand years and it has cracked, crumbled and split into pieces. Nobody hit it. So what did?

One boulder, two thousand years

Pick the weather, then let time pass
Illustration

What is the weather doing?

Today 2,000 years

0 years

Try all four. Which one works fastest? Which one needs a cold place? Which one needs a desert?

Key idea

Weathering breaks rock into smaller pieces where it is. The pieces stay put until something moves them.

On a hot day the outside of a rock warms and swells. On a cold night it shrinks. Do that a million times and the outer layer flakes off. Water that gets into a crack swells when it freezes and pushes the crack wider. Sand carried by the wind scrubs rock like sandpaper. Roots grow into cracks and push them apart. Water also slowly changes some rocks: Uluṟu’s red surface is iron in the rock rusting as water and air get at it.

Which of these is weathering?

Try it for real: three kinds of weathering in a week

  1. Wind and sand. Put six sugar cubes in a jar with a lid. Shake it two hundred times. Tip them out. What happened to the corners? What is the powder?
  2. Ice. Soak a piece of chalk in water for an hour, then put it in the freezer overnight in a bag. Look at it next to a dry piece.
  3. Roots. Mix plaster of Paris in a paper cup with three bean seeds pushed into it. Keep it damp for a week. Watch what the sprouting beans do to the plaster.

All three are models. The jar does in a minute what wind takes centuries to do.

What I noticed

2Test

Carried away.

Weathering makes the pieces. Rain and rivers move them. Here is a stream table: a tray of soil propped up on books, with a watering can for rain and a bowl at the low end. Change the slope, the rain and the plants, run the rain, and measure how much soil ends up in the bowl. Change one thing at a time and you have a fair test.

Rain on a tray of soil

Change one thing at a time
Model

Slope

Rain

Plants

Soil in the bowl 0 g

Pick your settings, then run the rain. The bowl catches whatever washes off the tray.

A run is a fair test when only one setting is different from the run before it. Then you know what made the difference.

Key idea

Steeper, wetter and barer means more erosion. Plants hold the soil together and slow the water down.

Each raindrop knocks grains loose. Water running downhill picks the loose grains up. The faster the water, the more it can carry, and water runs fastest down a steep, bare slope. Grass and tree roots hold the soil, and leaves break the fall of the rain.

Jo runs the stream table twice. Run 1 is steep, heavy rain, bare soil. Run 2 is gentle, light rain, grass. Run 2 loses much less soil. Jo says: “Grass stops erosion.” Is that a fair test?

My runs

3Explain

Where the pieces stop.

A fast river can carry pebbles, sand and mud all at once. When it slows down it has to let go, biggest pieces first and smallest last. That is deposition, and it is how rivers build flat plains, beaches and deltas out of the mountains they have worn down.

Fast river, slow river

Slide the speed
Illustration
Mountain stream, fast The sea, still

In a flood the river spills over its banks. Out on the plain the water is shallow and slow, so it drops its mud there. That is how a floodplain gets a new layer every few years.

Weathering

Rock breaks into smaller pieces where it is. Heat and cold, ice, wind-blown sand, roots and water all do it. It makes sediment.

Erosion

The pieces are picked up and moved away from where they were made. Rain, rivers, waves, wind and ice do the picking up.

Transportation

The pieces travel. Fast water carries pebbles, slower water carries sand, and even gentle water carries mud. Wind carries sand and dust.

Deposition

The water or wind slows down and drops what it was carrying. Pebbles drop first, then sand, then mud. The dropped pieces build up as layers.

Northern Territory · Kakadu floodplains

A sea of fresh water, every wet season

  • What happensEvery wet season, shallow fresh water spreads over the plains for hundreds of square kilometres. The floodwater carries mud and nutrients that feed the plants, birds, fish and crocodiles of the wetlands.
  • Where the mud came fromThe sandstone escarpment behind the plains is being worn back by up to one metre every thousand years. Its grains end up on the floodplain and the tidal flats, and some are carried out to sea.
  • Slow or rapid?One flood lays down one thin layer. The whole plain took thousands of floods.
Bangladesh and India · Ganges-Brahmaputra delta

The biggest river delta in the world

  • What happensThe Ganges and Brahmaputra rivers carry huge loads of sediment down from the Himalaya, the highest mountains on Earth, and drop it where they meet the Bay of Bengal. The delta they have built is about 350 kilometres wide.
  • The monsoonMost of the carrying happens in the summer monsoon, when months of heavy rain swell the rivers. Where the Brahmaputra reaches flat land, it slows and drops so much sand that it splits into many channels around the sandbars it makes.

A fast river full of pebbles, sand and mud flows into a lake and slows right down. What happens to its load?

The four words in order

4Apply

Slow or rapid?.

Some changes to Earth’s surface take millions of years. Some take seconds. All of these happened for real. Read each one and decide: slow, or rapid?

Ten real changes

0 of 10 sorted

Key idea

Rapid changes usually come at the end of slow ones.

The sea stack at the Twelve Apostles fell in a few seconds, but waves had been hollowing it out for thousands of years before that. A landslide takes a minute, after rain has soaked a slope that weathering had been loosening for centuries. Slow and rapid are two ends of the same story.

Which of these is a rapid change?

Near you

4Apply

People change the pace.

Clear the trees off a hillside, drive cattle over it or dig it up for a road, and one storm can wash away soil that took centuries to form. People can slow erosion down too. Use what you found at the stream table.

One hillside, three choices

Then make it rain
Illustration

Eastern Australia · 23 September 2009

Red Dawn: a dust storm that took the topsoil with it

  • What happenedAfter years of drought, strong winds lifted dry topsoil off farmland and dry country in western New South Wales, South Australia and south-west Queensland. The dust cloud was about 3,000 kilometres long and turned the sky over Sydney red.
  • How muchScientists worked out that more than 2.5 million tonnes of soil blew out over the sea in a single day. Cleaning up cost about 300 million dollars.
  • Slow or rapid?Rapid. Soil forms over centuries. This was wind erosion of a whole region in one afternoon, and bare, dry ground made it possible.

A farmer clears every tree and all the grass off a steep paddock. What will the next heavy rain do?

Erosion detective

4Apply

Salt in the fresh water.

On a flat coast, a low ridge of sand is sometimes all that keeps the sea out of a freshwater swamp. When floods and storm tides cut through the sand, salt water creeps in and the swamp starts to die. At Point Farewell in Kakadu, this has been happening since the 1950s.

Point Farewell, 1950 to 1997

Drag through the years
Illustration, simplified
1950 1997

1950

Northern Territory · Kakadu National Park

What the salt took

  • What happenedBig wet-season floods, storm surges and very high tides cut through the old beach ridges and the bank of soil that had kept the sea out of a freshwater wetland near Point Farewell. A tidal creek pushed inland: about 1 kilometre in 1950, about 4 kilometres by 1997.
  • What it didSalt water killed the paperbark forest. More than half of it was gone by 1997, and bare salty mudflats had grown almost ten times bigger. When the flats dry out they crack, and the wind blows their soil away, so the basin gets lower still.
  • Why it mattersBininj, the Aboriginal people of this part of Kakadu, hunted magpie geese and gathered their eggs here, and the springs in the swamp were a dry-season water source. The geese have gone from the Point Farewell wetlands.
  • What was triedA barrage, a wall across the creek, was built to keep the tide out. The tide wore it away and went around it. Scientists are still working out how to build walls that last, and whether the salt can be kept out of some parts of the plain at all.

Before you investigate a place

Every place in Australia is someone’s Country. Ask before you go.

Scientists who want to study a wetland, a beach or a creek on Aboriginal land ask the Traditional Owners first, and plan the work with them. Some places are not to be visited at all. Your class should do the same before a field trip: find out whose Country it is and what permission you need.

Why did the paperbark forest at Point Farewell die?

Think about it

5Show what you know

Plan your own fair test.

Scientists ask one question at a time. Pick a question about erosion, decide what you will change, what you will measure and what you will keep the same. Then run it, on the stream table or in a real tray of soil.

My fair test

My question

Make a real stream table

  1. Fill a paint tray, a baking tray or a cut-down milk carton with damp soil, patted flat. Prop one end up on a book: that is your slope.
  2. Put a bowl or a cut-off bottle at the low end to catch what washes down.
  3. Pour one cup of water from a jug with holes in the lid, or a watering can, from the same height each time. That is your rain.
  4. Pour the muddy water in the bowl through a coffee filter or a paper towel. Let it dry. Weigh the soil, or compare the piles by eye.
  5. Change one thing: two books instead of one, two cups of water, or a patch of grass cut from the lawn laid on the soil. Run it again. Compare.

Do it outside or on a tarp. Wash your hands afterwards, keep the soil out of your mouth and eyes, and ask before you dig up any grass. The printable sheet has a table for three runs.

Look at your own place

Use a map or an aerial photo to predict where erosion is happening near your school, then go and look.

Steep slopes, bare ground, creek banks, cattle tracks and building sites are the places to check. Take photos, measure a gully with a tape, and come back after the next big rain to measure it again. Find out whose Country the place is on and ask for permission if you need it, and plan how to stay safe near water and loose ground.

5Show what you know

Show what you know.

Five questions, one try each. They match the five “I can” statements from the start. At the end you will see which parts to look at again.

Every winter, water in the cracks of a mountain boulder freezes, and each year the cracks get a little wider. Which word describes this?

Which hillside will lose the most soil in a storm?

A muddy river in flood spreads out across a flat plain and slows right down. What happens to the sand and mud it was carrying?

Which of these is a rapid change to Earth’s surface?

Sam wants to find out whether grass slows erosion. Which plan is a fair test?

Offline activity

Plan a fair test

A planning sheet and a results table for a real stream table: what you will change, measure and keep the same, three runs, and what you found out.

Activity sheet (PDF) Editable (Word)
For teachers

Curriculum

Australian Curriculum: Science, Version 9. Year 5, Science Understanding, Earth and space sciences.

AC9S5U02: describe how weathering, erosion, transportation and deposition cause slow or rapid change to Earth’s surface

The lesson is built around the Year 5 Science Inquiry descriptions as much as the content description:

AC9S5I02: plan and conduct repeatable investigations to answer questions, including, as appropriate, deciding the variables to be changed, measured and controlled in fair tests; describing potential risks; planning for the safe use of equipment and materials; and identifying required permissions to conduct investigations on Country/Place

From the Year 5 achievement standard:

They describe key processes that change Earth’s surface. [...] Students plan safe investigations to identify patterns and relationships and make reasoned predictions. They identify risks associated with investigations and key intercultural considerations when planning field work. They identify variables to be changed and measured. They use equipment to generate data with appropriate precision. They construct representations to organise data and information and describe patterns, trends and relationships.

All three are quoted from ACARA’s Australian Curriculum Version 9.0.

Of the seven elaborations for AC9S5U02, the lesson works through all of them: mechanical and biological weathering (screen 2: heat and cold, ice, wind abrasion, roots); erosion by moving air and water and the relocation of surface soil (screens 3 and 6); the difference between weathering and erosion and their timescales (screens 2, 4 and 5); modelling erosion on a simulated landscape and the factors that reduce it (the stream table, screens 3 and 8); human changes to landscapes and their effect on erosion rates (screen 6); First Nations Australians affected by rapid sand dune erosion and saltwater reaching culturally significant freshwater swamps (screen 7, Point Farewell); and monsoon rainfall moving river sediment in the Asia-Pacific region (screen 4, the Ganges-Brahmaputra delta and Kakadu). The AC9S5I02 elaboration on using a map or aerial photograph to predict local erosion sites and planning a field excursion is on screens 6 and 8, and the elaborations on permission and consultation on Country are on screens 7 and 8.

How the lesson is taught

The lesson is a fair-test inquiry. Each screen asks a question that can be answered by changing one thing and watching what happens, and the stream table on screen 3 records every run and says whether it was a fair test against the run before it.

  • Look (screen 2): four agents of weathering on one boulder, with time as the slider. Students see that nothing moves; the rock just breaks.
  • Test (screen 3): the stream table. Slope, rain and plant cover, one at a time. The results table is the Year 5 “representation to organise data”.
  • Explain (screen 4): deposition in order of size, then the four words, then two real places where the sediment ends up.
  • Apply (screens 5 to 7): ten real changes sorted into slow and rapid; people speeding erosion up and slowing it down; salt water in a Kakadu wetland.
  • Show what you know (screens 8 and 9): the student’s own fair-test plan, with a check that it changes one thing, and five questions mapped to the “I can” statements.

Allow three sessions: screens 1 to 3, then 4 and 5, then 6 to 9. The real stream table on screen 8 is best done as a class after screen 3, with the printable sheet. The sugar cube, chalk and bean models on screen 2 take a week for the beans.

Misconceptions the screens target

  • Weathering and erosion are the same thing (screens 2, 4, 9). Weathering breaks; erosion moves.
  • Changes to the land are always slow (screen 5). Landslides, collapses, floods and dust storms are erosion and deposition in hours or seconds.
  • Rapid events come from nowhere (screen 5). The stack that fell in 2005 had been undercut for thousands of years.
  • Rivers only take land away (screen 4). Deposition builds floodplains, beaches and deltas, and the biggest pieces drop first.
  • Plants have nothing to do with soil loss (screens 3 and 6). Cover is the variable students can change most easily, in the model and on real land.
  • A test with a different result is a fair test (screens 3 and 9). The question is what was changed, not what was measured.

Hands-on versions and safety

  • Stream table: trays, damp soil, books for slope, a jug with holes in the lid for rain. Outside or on a tarp. Wash hands; no soil near eyes or mouth; ask before cutting a grass patch from a lawn.
  • Sugar cubes in a lidded jar for abrasion; chalk soaked and frozen in a bag for ice; bean seeds in plaster of Paris in a paper cup for roots (plaster warms as it sets; adults mix it).
  • Field work near a creek or a gully: plan it with the AC9S5I02 elaborations in mind: risks, equipment, and whose Country it is.

About the places and the numbers

  • Twelve Apostles: the limestone is 8.6 to 14 million years old and the stacks were shaped by coastal erosion only in the last few thousand years, after the last ice age (University of Melbourne, 2026). A stack about 50 metres tall collapsed in July 2005, leaving eight; news reports at the time said it took a few seconds.
  • Great Ocean Road: more than 120 landslides after heavy rain in September and October 2016; VicRoads crews cleared more than 10,000 tonnes of material (Premier of Victoria, 16 November 2016).
  • Red Dawn: total soil loss estimated at over 2,540,000 tonnes, a plume about 3,000 kilometres long, dust from north-western NSW, south-west Queensland and north-eastern South Australia, and a cost of about A$299 million, mostly household cleaning (Tozer and Leys, 2013).
  • Cyclone Alfred, March 2025: beaches lost millions of cubic metres of sand, leaving dune escarpments up to 6 metres high (Bureau of Meteorology).
  • Kakadu: wet-season floodwater spreads over the plains for hundreds of square kilometres; the escarpment erodes by up to one metre every thousand years (Parks Australia). Point Farewell: the tidal creek reached about 1 kilometre inland in 1950 and about 4 kilometres by 1997; bare saline mudflats had increased almost ten times since 1950 and more than half the paperbark forest had been lost; magpie geese, a traditional food, had disappeared from the wetlands; an earlier barrage eroded and was outflanked by the tide (Supervising Scientist note). The screen-7 picture is a simplified diagram, not a map.
  • Uluṟu: arkose, started forming about 550 million years ago, tilted 90 degrees about 400 million years ago; its flaky red surface is iron rusting as water and oxygen break down minerals, and the grey inside the caves is the rock’s original colour (Parks Australia).
  • Ganges-Brahmaputra: the world’s largest delta, about 350 kilometres wide (NASA JPL); the Brahmaputra has one of the highest sediment loads per square kilometre of any river and widens twentyfold into braided channels where it slows on reaching flat land (NASA Earth Observatory).
  • The stream table is a teaching model. Its grams are made up so that runs can be compared; they are not measurements of any real hillside. The weathering boulder compresses two thousand years into a slider, and the relative speeds of the four agents are a simplification: in a real place they depend on climate, rock type and water.

Answers at a glance

  • Slow or rapid: slow are Uluṟu flaking, Nitmiluk Gorge, the Kakadu escarpment, the Ganges-Brahmaputra delta, and Uluṟu rusting red; rapid are the Twelve Apostles collapse, the Great Ocean Road landslides, Cyclone Alfred’s beaches, Red Dawn, and a Kakadu flood laying down one layer.
  • Stream table: steep, heavy and bare gives the most soil; grass roughly halves it and trees with grass cut it further. Any run that changes two settings is flagged as not a fair test.
  • Exit check: x1 weathering; x2 steep bare slope; x3 dropped on the plain; x4 the stack collapsing; x5 same slope and water, only the grass changed.

Saved progress

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Sources

Word list