Rounded potholes cut into dark bedrock beside flowing water in the Presque Isle River, Michigan.

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Preparing the 3D view

Preparing lighting and the first complete frame…

Model scale

60 × 40 m terrain. vertical ×1.5. retreat prescribed, not dated.

Water flows downstream; the waterfall retreats upstream by 8.8 m in this chosen sequence. Change Retreat to expose a longer gorge.

How to read these results

Play follows flow only. No erosion rate, sediment budget or landform age is inferred. Select a feature, rotate the model and compare the real photograph.

River erosion

Explain how river erosion forms waterfalls, gorges and potholes, and distinguish the retreat of a waterfall from the direction of flow.

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

Why it happens

Flowing water can detach and transport material from a river’s bed and banks. Hydraulic action and abrasion contribute to erosion, while differences in rock resistance can influence the resulting forms.

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Presque Isle River, Michigan. Sediment circulating in eddies abrades the bedrock, enlarging these potholes.

Try a comparison

Change Retreat to move the lip upstream; select Pothole or V-shaped valley.

Reading the result

The selected stages explain mechanisms and changing form; they do not assign a measured erosion rate to a real river.

A common misunderstanding

Weathering and river erosion describe the same process.

Weathering breaks down or alters rock in place, while erosion wears away and removes material. A river can exploit rock weakened by weathering and use transported sediment to abrade its bed. The processes can work together without being interchangeable.

Cases

Exam language

Nick point

An abrupt steepening in a river’s long profile, also written knickpoint. A waterfall is one example. Resistant rock, uplift or a change in base level can produce one, and erosion may cause it to migrate upstream.

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Cwmorthin waterfall and plunge pool, Wales. Falling water and entrained sediment erode the pool below the step in the river bed.

Gorge

A narrow, steep-sided valley. One way it can develop is through the retreat of a waterfall, leaving a deeply cut channel downstream. The surrounding rock and the river’s erosive history control its form.

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Wutach Gorge, Germany. Capture diverted drainage from the Danube system towards the Rhine; subsequent incision cut this gorge.

Plunge pool

A deep hollow at the foot of a waterfall, enlarged by turbulent water and sediment striking the bed. Undercutting and collapse may contribute to waterfall retreat. The pool’s form also depends on rock structure, discharge and sediment supply.

Pothole

A rounded hollow eroded into a rocky riverbed by turbulent water and circulating sediment. Trapped stones may assist abrasion as water swirls. It differs from a large plunge pool formed directly beneath a waterfall.

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Presque Isle River, Michigan. Sediment circulating in eddies abrades the bedrock, enlarging these potholes.

V-valley

A valley with a broadly V-shaped cross-section, commonly developed where river downcutting and slope processes work together. Its form depends on rock, climate and erosion history. A V shape is evidence to interpret, not proof of one process acting alone.

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USGS Mount Rainier topographic sheet, published in 1971. Contours connect equal elevations; close spacing marks steep slopes.

Hydraulic action

Erosion caused by the force of moving water, including pressure fluctuations and water or trapped air acting within cracks. It can loosen material from a riverbank or coast. Abrasion adds the separate effect of sediment striking those surfaces.

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A breaking wave at Porto Covo, Portugal. In shallow water a wave slows and steepens; its crest eventually breaks.

Abrasion

The wearing away of rock by sediment carried against it by water, wind or ice. Look for scratches, polished surfaces or potholes. Unlike attrition, abrasion describes damage to the surface being struck, rather than collisions between transported particles.

Attrition

The breakdown and rounding of transported particles as they collide with one another. Pebbles may become smaller and smoother during repeated transport. This differs from abrasion, in which those particles wear away the bed, bank or another fixed surface.

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Pebbles on the North Sea coast of England. Repeated collisions can round and reduce fragments through attrition; a still image records the resulting grains.

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