Field photographs of red and black soils at different positions on the Addi Selam hillslope in Ethiopia.

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Preparing the 3D view

Preparing lighting and the first complete frame…

Model scale

Soil thickness ×20. 120 m hillslope. topographic slope to scale.

Soils share the same parent material, but their position on the slope changes drainage and sediment movement: the crest and backslope lose material, while the toe receives water and sediment.

How to read these results

Change Slope to compare a prescribed sequence. Only soil thickness is enlarged in the teaching view. Soil development, erosion and deposition rates are not calculated.

Soil catena

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

Drag to rotate. Hold Ctrl and scroll to zoom, or pinch on a touch screen.

Why it happens

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.

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Addi Selam, Ethiopia: published field photographs compare red and black soils along a hillslope. Slope position changes drainage and material movement.

Try a comparison

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

Reading the result

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

A common misunderstanding

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.

Cases

Exam language

Catena

A sequence of soils along a slope whose differences are related to relief, drainage and movement of sediment. Compare a freely drained crest with a wetter footslope. A catena need not form a perfectly regular sequence in every landscape.

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Addi Selam, Ethiopia: published field photographs compare red and black soils along a hillslope. Slope position changes drainage and material movement.

Crest

The highest part of a hill or ridge. Soil thickness and drainage there depend on the local relief, geology and climate.

Backslope

The main, usually steep section of a hillslope between its shoulder and footslope; material commonly moves through it downslope.

Toe

The downslope end of a landslide or other mass-movement deposit. Displaced material may thicken or bulge there as it slows. It differs from the crown, where material separates from the stable slope.

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Oso, Washington, 2014: an aerial photograph of the landslide source, travel path and deposit. The displaced material crossed the valley floor.

Gley

Soil features associated with prolonged saturation and oxygen shortage, often including grey colours and rusty mottles from changes in iron chemistry.

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Real clay samples showing contrasting redox conditions. Prolonged saturation restricts oxygen, often producing grey gley colours; oxidation can produce reddish mottles.

Ranker

A traditional soil term for a shallow, often acidic soil over hard, non-calcareous rock; commonly found on steep or exposed ground.

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Rankosol over granite on Île de Berder, France. A shallow organic-rich surface over non-calcareous bedrock illustrates a ranker; horizons are real field layers, not a template.

Colluvium

Loose sediment accumulated on or near the foot of a slope through gravity-driven movement and surface wash. It commonly contains a mixture of particle sizes. Unlike alluvium, it is not defined by deposition from a river channel.

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Calciustoll near Ponce, Puerto Rico: a Mollisol with a roughly 30 cm mollic surface over a calcic horizon. Its parent material includes colluvium and weathered limestone.

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