Earth system
Plate tectonics
The unifying framework of the solid-Earth sciences: a rigid outer shell broken into moving pieces, creating crust in some places and destroying it in others, at rates that balance.
The plates are lithospheric — crust plus rigid uppermost mantle — and each carries both continental and oceanic areas. They move over a weaker, slowly flowing asthenosphere.[1, 2]
Most motion is concentrated at four kinds of boundary: divergent, convergent, transform, and broad zones where deformation is distributed rather than confined to a line.[1, 2]
What drives it is not settled. Convection, ridge push and slab pull have each been argued to contribute, with slab pull favoured since the 1990s. What is settled is the bookkeeping: the planet is not growing, so crust is destroyed at the rate it is created.[1, 2, 3]
Read
How tectonic plates move
Plates diverge, converge and slide past one another along narrow boundary zones. Each style of boundary leaves a distinctive signature: new ocean floor, deep trenches and volcanic arcs, or long transform faults like the San Andreas.
Why tectonic plates move
The honest answer is that several forces contribute and their balance has been argued over for decades. What changed in the 1990s was not the discovery of the cause but a shift in which cause was thought to matter most.
How subduction works
Subduction is where the ocean floor ends. It carves the deepest features on the planet, builds volcanic chains, generates the largest earthquakes — and its central mechanism, how the magma is made, is still argued over.
How continents rift
Breaking a continent is a sequence, not an event — and it does not always finish. East Africa and the Red Sea are the same process caught at two different stages.
How ocean basins form
The largest mountain range on Earth is underwater, and it is a factory. Everything about the ocean floor — its age, its magnetism, its eventual disappearance — follows from what happens along that ridge.
How mountains form
Two plates collide and mountains rise is a description of one mechanism, not of mountain building. Ranges are raised in several different ways, and the Andes and the Himalaya are not the same story.
The plates
Major plates seeded because a sourced boundary relationship exists for each; the set is not a complete plate model.
Tectonic plate
Pacific Plate
The largest tectonic plate, dominantly oceanic, whose boundaries include the San Andreas transform system and the subduction zone marked by the Mariana Trench.
Tectonic plate
North American Plate
A major tectonic plate carrying most of North America, bounded on its west by the San Andreas transform system and on its east by the Mid-Atlantic Ridge.
Tectonic plate
Eurasian Plate
A major plate carrying Europe and most of Asia. It separates from the North American Plate along the Mid-Atlantic Ridge and converges with the Indian Plate along the Himalayan collision zone.
Tectonic plate
African Plate
A major plate carrying Africa and part of the surrounding ocean floor. It is being actively split in East Africa, where a new spreading centre may be developing.
Tectonic plate
Arabian Plate
A plate carrying the Arabian Peninsula, separated from the African Plate by the Red Sea — an ocean basin caught in the act of opening.
Tectonic plate
Indian Plate
The plate carrying the Indian subcontinent, whose collision with Eurasia raised the Himalaya and the Tibetan Plateau and continues to shorten the crust today.
Tectonic plate
Nazca Plate
An oceanic plate of the eastern Pacific that is being subducted beneath the South American Plate along the Peru–Chile trench, driving Andean uplift and seismicity.
Tectonic plate
South American Plate
A major plate carrying South America and the adjacent South Atlantic sea floor: overriding the Nazca Plate on its west, diverging from Africa on its east.
Tectonic plate
Philippine Sea Plate
An oceanic plate of the western Pacific. The fast-moving Pacific Plate converges against it, and the Mariana Trench marks where subduction occurs.
Divergent systems
Where plates separate and new crust is made — from continental rifting through to mature seafloor spreading.
Geological process
Continental rifting
The stretching, faulting and thinning of continental lithosphere, often accompanied by magmatism, which may progress to complete breakup and the formation of a new ocean basin.
Geological process
Seafloor spreading
The generation of new oceanic crust at mid-ocean ridges and its transport away from the ridge crest, progressively widening the ocean basin between the separating plates.
Rift
East African Rift
A zone of active continental rifting in East Africa where the lithosphere is being stretched, fractured and intruded by rising magma — a candidate site of a future spreading centre.
Rift
Red Sea Rift
The rift separating Arabia from Africa. It is further advanced than the East African Rift: continental breakup has already produced a narrow ocean basin.
Oceanic ridge
Global mid-ocean ridge system
The connected submarine mountain chain that winds around the entire planet at divergent plate boundaries. It is the largest topographic feature on Earth’s surface and the site where most new crust is made.
Oceanic ridge
Mid-Atlantic Ridge
A submerged mountain range extending from the Arctic Ocean to beyond the southern tip of Africa: one segment of the global mid-ocean ridge system, where new oceanic crust is generated as plates move apart.
Oceanic ridge
East Pacific Rise
A fast-spreading divergent boundary in the eastern Pacific. Near Easter Island it records the highest average rate of plate separation measured on the mid-ocean ridge system.
Geological structure
Krafla fissure zone
A fissure system in northeastern Iceland where rifting has been directly observed and measured — one of the few places where plate divergence can be watched happening on land.
Convergent systems
Where crust is destroyed or thickened: subduction, trenches, arcs and collision.
Geological process
Subduction
The process by which one plate sinks beneath another at a convergent boundary, recycling crust into the mantle and producing the deepest trenches, powerful earthquakes and volcanic arcs.
Geological process
Crustal recycling
The return of lithosphere to the mantle at subduction zones, which balances the creation of new crust at spreading centres and keeps the size of the Earth effectively constant.
Trench
Peru–Chile Trench
The trench marking where the oceanic Nazca Plate descends beneath the continental margin of South America — the convergent boundary responsible for the Andes and for the region’s great earthquakes.
Trench
Mariana Trench
An oceanic trench paralleling the Mariana Islands, marking where the Pacific Plate converges against the Philippine Plate. Its southern end holds the Challenger Deep, the deepest known point of the ocean floor.
Geological process
Continental collision
Convergence in which two continental plates meet and neither is subducted, because continental crust resists downward motion. The crust instead buckles, shortens and thickens.
Geological process
Crustal shortening
Horizontal compression that reduces the width of a region of crust and increases its thickness, expressed at the surface as folding and thrust faulting.
Geological process
Orogeny
Mountain building. Not a single mechanism but a family of them: collision, subduction-related uplift, crustal shortening and thrusting, magmatic addition, and extensional fault-block uplift can each raise topography.
Mountain range
Himalaya
The highest continental mountain range on Earth, raised by the ongoing collision between the Indian and Eurasian Plates.
Mountain range
Andes
The mountain chain forming the western backbone of South America, raised as the overriding South American Plate is lifted above the subducting Nazca Plate.
Mountain range
Alps
A collisional mountain belt of Europe. Beneath large ranges such as the Alps the base of the crust can lie far deeper than the continental average — mountains have roots as well as summits.
Mountain range
Cascade Range
A volcanic mountain range of the Pacific Northwest of North America, one of the classic expressions of arc volcanism above a subduction zone.
Geological structure
Tibetan Plateau
An immense elevated region north of the Himalaya, thickened and raised by the continuing collision of India with Eurasia. Its average elevation exceeds the summits of most mountains outside the great ranges.
Transform motion
Where plates slide past one another and crust is neither made nor destroyed.
Fault
San Andreas Fault
A transform fault zone slicing through two thirds of the length of California, connecting divergent boundaries to its north and south; one of the few transform faults exposed on land.
Geological process
Faulting
The fracturing of rock and displacement of the blocks on either side. The sense of that displacement — normal, reverse or strike-slip — records the orientation of the stresses that produced it.
Hub last updated 2026-09-06. Every entry above is a structured record; the bracketed references link to the entities whose claims support each statement.