Earth's Surface Seperated into Tectonic Plates
- Lithosphere is divided into sections called tectonic plates.
- Plated aare moving due to convection currents in the asthenosphere.
- Places where plates meey are called boundaries or plate margins
Tectonic Plates Move Due to Convection Currents in the Mantle
- Radioactive decay of some elements in the mantle and core e.g. urainium generates a lot of heat.
- Lower parts of asthenosphere heat up become less dense and slowly rise.
- As move towards top of asthenosphere they cool down, become more dense, then slowly sink.
- The circular movement of semi-molten rock called convection currents.
- Convection currents in asthenosphere create drag on base of teconic plates causing them to move.
Crust Created When Plates Move Apart
- Rising convection currents diverge at the base of the lithosphere.
- Drag of convection currents cause plates above to diverge too.
- Magma rises up to fill gap created, cools to form new crust.
- Over time new crust dragged apart and even more new crust forms between it.
- When this happens at a plate margin under sea the sea floor gets wider.
- Process is called sea floor spreading.
- Creates structures called mid-ocean ridges - ridges of higher terrain on either side of margin.
- Similar process of spreading occurs at land margins where plates are…