Soil Formation and Erosion
Introduced| English |
|---|
| weathering/ˈweðərɪŋ/ |
| humus/ˈhjuːməs/ |
| erosion/ɪˈrəʊʒn/ |
The thin skin that feeds us
- Almost all our food grows in a thin layer of soil.
- Soil is not just dirt — it is a living mix of rock, air, water, and life.
- It takes centuries to build, but can wash away in a day.
- Understanding how soil forms shows why we must protect it.
From rock to soil
- Soil begins as solid parent rock.
- Weathering 风化 slowly breaks the rock into ever-smaller pieces.
- Wind, water, freezing ice, and plant roots all do the breaking.
- Over long times, this produces the mineral grains of soil.
Soil forms when weathering breaks down…
Soil starts as weathered rock — broken down over long times into mineral particles.
Adding life
- Dead plants and animals decay and mix into the mineral grains.
- This dark, decayed organic matter is called humus 腐殖质.
- Humus holds water and nutrients, making the soil fertile.
- Living things — worms, fungi, bacteria — keep the soil healthy.
How soil forms
Step through soil formation - rock is broken down and mixed with organic matter over long times.
The dark, decayed organic matter in soil is called…
Humus is decayed plant and animal matter; it makes soil dark and fertile.
Erosion strips it away
- Erosion 侵蚀 is the removal of soil by wind or water.
- Bare, ploughed, or deforested land erodes fastest.
- Erosion carries away the fertile top layer, leaving poor ground.
- Because soil forms so slowly, erosion is a serious threat.
The removal of soil by wind or water is called ____.
Erosion carries soil away — and it happens far faster than soil forms.
Soil forms slowly but can be eroded away quickly, so it is a limited resource.
It can take centuries to build an inch of soil, but erosion can strip it in a single storm.
Select all true statements about soil formation and erosion.
Soil forms slowly, over centuries. The other three are correct.
Soil is a slowly renewable resource, close to non-renewable on human timescales. It can take centuries to form an inch of fertile soil, but a single storm on bare ground can erode it away. Once the fertile topsoil is gone, it is effectively lost for generations.
The Dust Bowl:
- In the 1930s, farmers ploughed up huge areas of dry grassland in the US.
- With no roots to hold it, the bare soil dried out.
- Great winds lifted the topsoil into towering dust storms, ruining the land — a disaster of soil erosion caused by removing the plants that protected it.
Soil forms slowly: weathering breaks parent rock into mineral grains, and decayed organic matter (humus) makes it fertile. Erosion by wind and water removes soil far faster than it forms. Because soil builds over centuries but erodes in days, it is a precious, easily lost resource.