Geog Theme 3

• the earths inner core is very dense and solid
• the earths outer core is liquid iron and nickel
• The core is the hottest part of the earth and the temperature ranges from 400-6000°c
• The earths mantle surrounds the earths core and is made of semi molten rock that can move
• The temperature of the mantle ranges from 1000-3700°c
• The crust of the earth is very thin it’s between 5-100km thick
• The two types of crust are the continental crust which is thicker and less dense and the oceanic crust which is thinner and denser these are tectonic plates
• Continental plates are thicker, older and lighter so they don’t subduct
• Oceanic plates are thinner, younger, and denser so they can subduct under another plate
• Plate boundaries describe the location on earth where 2 tectonic plates meet or sit next to eachother
• Tectonic plates move according to the movements below in the mantle
• Because tectonic plates float on the mantle, convection currents in the asthenosphere create drag, making them move
• Convection currents in the mantle:


  Radioactive decay in the earths mantle and core generates heat

  the lower part of the asthenosphere heats up

  the lower parts of the asthenosphere become less dense and start to rise

  the hot rock in the asthenosphere gets cooler as it is further away from the earths core. It becomes denser and sinks
• At conservative plate boundaries, plates slide past eachother in opposite directions or in the same direction at different speed
• At constructive plate boundaries, the plates move apart the convection currents push apart and cause a gap between the plates. Magma rises up to fill this gap
• At a destructive plate boundary plates are moving towards eachother