Rocks and soil
Recognise that soils are made from rocks and organic matter, and that different soils have different properties
What a learner can do afterwards
- State that soil is a mixture of broken-down rock particles and decomposed organic matter (humus)
- Compare at least two types of soil (sandy, clay, loam) and describe their different properties
- Explain that soil formation takes a very long time as rocks gradually break down
The lesson
Soil looks like plain brown dirt, but it is really a mix of two things: tiny broken pieces of rock, and humus, which is rotted-down bits of dead leaves, plants and creatures. Together they make the soil that plants grow in.
Big rocks slowly break into smaller and smaller pieces. Rain, wind, ice, and even plant roots squeeze into tiny cracks and split rocks apart, bit by bit, over a very long time.
Zara pushes her finger into three pots of soil. The sandy soil feels gritty and crumbly. The clay soil feels smooth and sticky when wet. The loam soil feels soft and crumbly, a good mix for growing seeds.
Soil forms so slowly that it can take hundreds of years just to make a layer as thick as your finger. That is why we look after the soil we have.
Soil is broken rock mixed with humus, sandy, clay and loam soils behave differently, and soil takes a very long time to form.
Watch it
Where it sits
Learn first
This opens up
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.