ACARA v9 CONTENT DESCRIPTION “describe how weathering, erosion, transportation and deposition cause slow or rapid change to Earth’s surface”
Builds on knowing that the land is made of rock and soil, and that water moves through the landscape. Here we follow four linked processes that slowly or quickly reshape the surface of Earth: weathering, erosion, transportation and deposition.
Four processes shape the land
The hills, valleys, rivers and beaches around us are always changing. Four processes work together to reshape the surface of Earth. Weathering breaks rock into smaller pieces. Erosion carries those pieces away. Transportation moves them along, often in a river. And deposition drops them somewhere new, building fresh landforms. The same processes can act slowly over millions of years or rapidly in a single day.
Weathering breaks rock apart
Step through how a solid rock is broken into smaller pieces right where it sits.
Weathering is the breaking of rock into smaller pieces while it stays in the same place. Rain, wind and changing temperature all wear at the rock. When water trickles into a crack and freezes, it pushes the crack wider, until the rock splits into loose pieces.
Weathering: breaking rock into pieces
Weathering is the breaking down of rock while it stays in the same place. Rain, wind and changing temperature all wear at the rock over time. One common way is freezing: water trickles into a tiny crack, freezes and expands, and pushes the crack wider. After many cycles the rock splits into loose fragments. Weathering does not move the rock, it only breaks it.
Erosion carries the pieces away
Switch between wind and flowing water to see how loosened pieces are moved off the slope.
Once weathering has loosened the pieces, erosion picks them up and carries them away. Wind blows light grains across the land, and flowing water washes sediment down a slope. Erosion is the moving of the loosened material, not the breaking.
Erosion: carrying the pieces away
Once weathering has loosened the pieces, erosion picks them up and moves them off the slope. Wind lifts and blows light grains across the land, and flowing water washes sediment downhill. Erosion is about moving the loosened material away, not about breaking it. Where erosion is strong, the land can lose soil and wear down.
Transportation: the river carries it along
Step the bundle of sediment downstream and watch the river carry it toward the sea.
Transportation is the journey the loosened material takes. A river picks up sand, mud and small stones and carries them along in its flowing water, sometimes for many kilometres, moving them from the hills toward the sea.
Transportation: the journey of the sediment
Transportation is the journey the loosened material takes from one place to another. A river is a powerful carrier: it sweeps sand, mud and small stones along in its flowing water, sometimes for many kilometres. Wind, waves and even moving ice can transport material too. The faster the water flows, the bigger the pieces it can carry.
Deposition builds new land
Add layers of dropped sediment and watch a delta grow where the river slows.
Deposition is the dropping of carried material when the water or wind slows down. Where a river meets a calm sea it loses speed and lets go of its load. The sediment settles and builds up, layer on layer, into new landforms such as a delta, a beach or a sandbar.
Deposition: dropping the load and building land
When moving water or wind slows down, it can no longer carry its load, so it drops the material. This is deposition. Where a river meets a calm sea it loses speed and lets the sediment settle. Layer on layer, the dropped material builds new landforms such as a delta, a beach or a sandbar. So the very material weathered from one place can build up the land somewhere else.
Slow change or rapid change
Switch between a slowly carved canyon and a sudden landslide to compare how fast land can change.
These same processes can be slow or rapid. A river may take millions of years to carve a deep canyon, grain by grain. A landslide or a flood can move huge amounts of rock and soil in seconds. Both reshape the land, just at very different speeds.
Slow change and rapid change
These processes can be slow or rapid. A river may take millions of years to carve a deep canyon, removing the rock grain by grain. Yet a landslide or a flood can move enormous amounts of rock and soil in just seconds. Both kinds of change reshape the surface of Earth, one quietly over ages and the other suddenly.
Why this matters
Weathering, erosion, transportation and deposition together shape the world we live on, from mountain valleys to the sandy beach. Understanding them helps you read the landscape, see why rivers carry mud, and explain how floods and landslides can change a place quickly. It also helps people protect soil, plan where to build, and care for the land.
Quick self-check
1. What does weathering do to a solid rock?
2. A strong wind blows loose sand off a dune and away across the land. What is this an example of?
3. How does a river take part in transportation?
4. Where a river slows down as it meets a calm sea, sediment settles and builds up. What is this called?
5. Which of these is an example of rapid change to the land?