Soil Layers and Life on Earth
GeographySoils, Biosphere & EnvironmentAges 11–12
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Soils, Biosphere & Environment
On the left, a soil profile forms over time: click Run to see the litter, humus and accumulation layers thicken above the parent rock; change the climate, parent rock and slope to see why steep mountain soils stay thin while alluvial and basaltic soils grow thick and fertile. On the right, a vegetation column by latitude (tropical rainforest, savanna, desert, broadleaf forest, taiga, tundra) and a mountain show that vegetation also changes with altitude, just as it does from the Equator to the poles. Drag the latitude arrow or click a soil layer to read an explanation.
Lesson: Soil on Earth; life on Earth
What it shows
Soil forms slowly as parent rock weathers and organic matter from plants and animals is added and broken down. The model grows a soil profile year by year: a litter layer on top, a dark humus layer, a paler accumulation layer where rainwater deposits clay, and the parent rock beneath. How deep and fertile the soil becomes depends on the five soil-forming factors: parent rock, climate, organisms, relief and time. A second panel links vegetation to climate, showing the natural biomes from the Equator towards the poles and the matching altitudinal belts on a mountain, where temperature falls about 0.6 °C per 100 m.
How to use
Start with a wet tropical climate, basalt parent rock and a gentle slope, press Run and let the profile grow until its depth levels off. Press Reset, then change one factor at a time (Climate where the soil forms, Parent rock or Slope of the terrain) and compare the humus and total soil depth. Click any layer to read what it is. Finally, drag the Latitude for viewing vegetation from 0° to 85° and compare the biome sequence with the mountain belts.
Parameters you can change
- Climate where the soil forms Wet tropical (hot, heavy rain), Temperate (cool, moderate rain), Arid (hot, very little rain), Polar (freezing cold)
- Parent rock (source material) Basalt, Granite, Limestone, River alluvium
- Slope of the terrain 0–35 °
- Latitude for viewing vegetation 0–85 ° (North)
- Time simulation speed 20–600 years/s
Questions to explore
- Why is the soil on a steep slope thinner than on flat ground with the same climate and parent rock?
- Which parent rock gives the thickest, most fertile soil, and what does this show about where soil minerals come from?
- How does the sequence of vegetation belts up a high mountain compare with the change from the Equator to the poles?
