Plate tectonic theory of crustal evolution: tectonic plates, plate movement, gravitational sliding, ridge push, slab pull, convection currents and sea-floor spreading
Earth's outer shell is broken into large rocky slabs called tectonic plates. Several forces — including heat-driven currents in the mantle below — keep these plates moving slowly but constantly.
Real World
GPS satellites measure the Eurasian and North American plates diverging along the Mid-Atlantic Ridge at roughly 2.5 cm per year — about the rate a fingernail grows — confirming slab pull and ridge push are real, measurable forces.
Exam Focus
Distinguish clearly between the driving mechanism (e.g. slab pull) and the evidence for it; confusing the two loses marks.
Essay Framework
Use PEEL to structure every paragraph. Tap each step for guidance and an example.
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