Long fault-bounded valleys and escarpments in Kenya's East African Rift, viewed from the ISS.

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Preparing the 3D view

Preparing lighting and the first complete frame…

Model scale

Vertical dimensions ×2. idealised 300 km section through a basin.

Formation stage3/6: Open ocean. Extension and spreading can open a basin.

How to read these results

Select a stage to compare the structure. The reference continental crust is 35 km thick and oceanic crust about 7 km thick.

Wilson cycle

Follow the opening and closing of an ocean basin and relate continental collision to the formation of mountain belts.

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Why it happens

Continental rifting can open an ocean basin, while subduction can later consume oceanic lithosphere and bring continents together. Mountain belts can preserve evidence of oceans that have closed.

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The East African Rift in Kenya: continental extension is an opening stage of a possible ocean-basin cycle. A rift does not inevitably become an ocean.

Try a comparison

Switch to Subduction begins and follow the slab. Compare Ocean closes with Continental collision and identify the root.

Reading the result

The six stages organise possible tectonic changes; they are not a fixed schedule followed by every ocean basin.

A common misunderstanding

Every ocean basin follows the same fixed timetable from opening to closure.

The Wilson cycle organises possible stages of rifting, ocean spreading, subduction and collision. Real basins differ in geometry, plate motions and duration, and some rifts stop developing. The framework helps interpret geological evidence without prescribing one schedule for every ocean.

Cases

Exam language

Wilson cycle

A framework describing the opening and eventual closing of an ocean basin through rifting, seafloor spreading, subduction and continental collision. Different basins follow different histories. Geological structures can preserve evidence of stages even after an ocean has disappeared.

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The East African Rift in Kenya: continental extension is an opening stage of a possible ocean-basin cycle. A rift does not inevitably become an ocean.

Rift

An elongated region where the lithosphere is extending and thinning. Some continental rifts develop into ocean basins; others cease spreading.

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Almannagjá, Þingvellir: faults accommodate extension within Iceland's broad North American–Eurasian plate boundary zone.

Passive margin

A transition between continental and oceanic crust that is not an active plate boundary. Many Atlantic margins developed after continental rifting. Sediment accumulation, subsidence and occasional earthquakes can still occur, so passive does not mean completely inactive.

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NOAA South Atlantic bathymetry. Colour represents seafloor depth, revealing continental margins, abyssal basins and the Mid-Atlantic Ridge.

Orogeny

A period or process of mountain building involving deformation and thickening of the crust. Plate collision and subduction are common settings. Mountains may later be eroded, leaving folded rocks and other evidence of an older mountain belt.

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The Himalaya from the ISS: crust shortened and thickened as India collided with Eurasia.

Caledonides

An ancient mountain belt formed during Palaeozoic continental collisions, now exposed in places including Scotland, Scandinavia and Greenland.

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The Moine Thrust at Knockan Crag juxtaposes rocks with different geological histories. Such field contacts help reconstruct the Caledonian mountain belt and its crustal terranes; boundaries between terranes need regional evidence as well as one outcrop.

Appalachians

An ancient mountain belt in eastern North America, assembled through several Palaeozoic collisions during the closing of oceans and formation of Pangaea.

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NASA Terra MODIS, 15 September 2023. Appalachian ridges and valleys across Virginia, West Virginia, Maryland and Pennsylvania preserve the structure of an ancient mountain belt.

Terrane

A body of crust with a geological history distinct from neighbouring regions, often joined to a continent by tectonic accretion.

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Formation stage