Soil catena

Field photographs of red and black soils at different positions on the Addi Selam hillslope in Ethiopia. — Addi Selam, Ethiopia: published field photographs compare red and black soils along a hillslope. Slope position changes drainage and material movement.

A suggested lesson sequence

Use these stages at your own pace. Pause for students to sketch, compare observations or lead part of the demonstration.

01
Observe
Locate crest, backslope and toe on one parent material. Read the three soil thicknesses.
Open Observe
02
Tinker
Increase Slope and compare export and accumulation in this selected example. Compare physical scale and distinguish soil thickness from topographic relief.
Open Tinker
03
Explain
How can movement of water and sediment connect soil differences along a single slope?
Open Explain
04
Check
Choose an answer and explain your reasoning. Each question includes feedback.
Open Check

Rehearse with the model

The same scene and controls as the lab. Load it when you are ready; use Start projector for the full classroom view.

Before the lesson

Compare soil profiles from the crest to the foot of a slope and explain how water and sediment movement connect them.

Open the model before the lesson and choose a view that makes the important feature easy to see. Drag to rotate, and use the on-screen controls to change one variable at a time. The Controls panel explains the available keyboard shortcuts.

Ask students to predict the result before you change a setting. Compare the new view with the starting state.

Guide the demonstration

Locate crest, backslope and toe on one parent material. Read the three soil thicknesses.

Increase Slope and compare export and accumulation in this selected example. Compare physical scale and distinguish soil thickness from topographic relief.

Discuss a common misconception

“Soils on one hillside must be identical because they share a climate.” Position on a slope affects drainage, erosion, deposition and the movement of dissolved material. These differences can produce contrasting soils even on similar parent material under the same regional climate. The pattern depends on local conditions rather than a universal sequence of thicknesses.

Build the explanation

Soils along a slope are linked by movement of water and sediment. Upper slopes may lose material while lower slopes receive it, creating differences even where parent material is similar.

Increase Slope and compare export and accumulation in this selected example. Compare physical scale and distinguish soil thickness from topographic relief.

The selected thickness pattern is one example; climate, drainage and land use can produce a different catena.

Teaching notes

Consider slope position, drainage and material movement alongside climate when comparing soils along a hillslope.

Use evidence of erosion and accumulation rather than assuming that the thickest soil must occur at the crest.

Distinguish a catena’s sequence of soil profiles from a texture triangle that classifies mineral particle proportions.

Check understanding

Open Check for 4 questions. Ask students to explain their choice before revealing the answer.

Return to the opening photograph. Ask students to identify one visible feature and explain which part of the model helps account for it.

Look more closely

Use these observations to connect the vocabulary to features students can identify.

Toe

An aerial view of the Oso landslide's bare source scar, debris path and deposits across the valley. — Oso, Washington, 2014: an aerial photograph of the landslide source, travel path and deposit. The displaced material crossed the valley floor.

Read the definition

Gley

Photographs of clay samples comparing grey reduced material and oxidised reddish material. — Real clay samples showing contrasting redox conditions. Prolonged saturation restricts oxygen, often producing grey gley colours; oxidation can produce reddish mottles.

Read the definition

Sources to keep beside the lesson

Cranfield / LandIS soils
USDA NRCS catenas