Plate tectonics explained: continents that move
Earth has 7 major plates moving 2 to 10 cm yearly, building mountains and causing quakes.
Plates that crawl like fingernails
Earth's outer shell holds 7 major and 8 minor plates, each 100 kilometers thick. They drift 2 to 10 centimeters yearly, as fast as fingernails grow, powered by hot mantle convection below.
New crust forms at mid-ocean ridges where magma rises across 65,000 kilometers of underwater mountains. Old crust sinks at subduction zones, melting 100 kilometers deep and fueling volcanoes.
Borders where Earth shakes
About 90 percent of earthquakes strike plate borders like the Pacific Ring of Fire. Plates stick for 100 years then slip meters in seconds, releasing energy of 30 atomic bombs for magnitude 7.
Satellites now track motion live with 2 millimeter accuracy. The Atlantic widens 2.5 centimeters yearly while Africa splits in the Rift Valley at 6 millimeters yearly toward a new ocean.
- 7 major plus 8 minor plates
- Speed 2 to 10 cm per year
- Ridges span 65,000 km
- 90 percent quakes at borders
- Atlantic widens 2.5 cm yearly