Theory Flashcards
What are the four layers of earth?
Inner core
Outer Core
Mantle
Crust
What is the inner core?
Located in the centre of the earth and also the hottest part of it.
It is solid and made up of iron and nickel with temperatures reaching 5,500 degrees.
Almost like the engine room of the earth with its immense heat energy.
What is the outer core?
Layer surrounding the inner core.
Liquid layer made up of iron and nickel just like the inner core.
Extremely hot with temperatures similar to the inner core.
What is the mantle?
Widest section of the earth.
Thickness of approximately 2,900 km.
Made up of semi-molten rock called magma.
What is the crust?
The outer layer of the earth.
Thin layer between 0-60 km thick.
Solid rock year upon which we live.
What are the 4 theories which support the principle of plate tectonics?
Mantle Convection
Sea floor spreading (palaeomagnetism)
Subduction
Slab Pull
What is mantle convection?
Movement in the lower mantle caused by heat from the inner core.
The heat produces by the decay of radioactive elements in the inner core heats the lower mantle.
Lower mantle starts to rise up to the top of the asthenosphere.
As magma reaches the top it begins to cool and drop back down into the mantle.
Means that mantle moves in circles and the plates on the lithosphere move whichever way the convection currents drive them.
What is slab pull?
At ocean ridges the plates are being pulled away from each other.
Hot magma is forced up from the asthenosphere and hardens to form new crust.
Crust cools making it denser and thicker.
This causes the plate to sink into the mantle more quickly under its own weight and pulls the rest of the plate down with it.
What is sea floor spreading?
In the 1950’s scientists studied palaeomagnetism. They found that every 400,000 years the earth’s magnetic field changes direction causing magnetic north and south poles to swap.
When lava cools the minerals inside the rock usually line up with the earths magnetic direction.
Minerals lined up exactly with the changes in the magnetic fields.
This shows that new rock must have been formed at the same time on both sides and proves tectonic activity and sea floor spreading.
What are mid-ocean ridges?
Formed when hot magma is forced up from the asthenosphere and harden to form new crust. Usually this happens when plates are moving away from each other.
What is subduction?
Where land is being created in one part of the world it is being destroyed in another through the process of subduction.
As two plates move towards each other one slides under the other one into the mantle.
The plate which slides under is melted and joins the mantle in the asthenosphere.
The area where it melts is known as the subduction zone.
What is asthenosphere?
The lower molten section of the mantle.
What is lithosphere?
The upper solid section of the mantle on which the crust sits.
