Wegener believed that the continents were once all together. he thought that South America and Africa were once together as the patterns on the countries matched up. Wegener thought that the sea floor was spreading out. In the 1960's the theory was proven right as the rock layers and fossils matched up
2 The Structure of the Earth
2.1 crust - relatively thin and rocky
2.2 mantle - has the properties of a solid, but can flow
2.3 outer core - made from liquid nickel and iron
2.4 inner core - made from solid nickel and iron.
2.5 Difficult To study
The radius of the core is just over half the radius of the Earth. The core itself consists of a solid inner core and a liquid outer core. It is difficult to study the structure of the Earth because:
the crust is too thick to drill all the way throughscientists need to study seismic waves made by earthquakes or man-made explosions.
3 Tectonic Plates
The Lithnosphere is the relatively cold rigid outer part of the Earth that includes the crust and part of the mantle. It is made of tectonic plates. These are less dense than the mantle below and move very slowly. The plates cause volcanoes and earthquakes where they grind together.
Subduction is when the continental and oceanic plates move together to create friction which creates earthquakes and volcanoes
The plates move because of convection currents in the semi-rigid mantle. Oceanic crust is denser than continental crust. Where tectonic plates meet, the oceanic plate goes under the continental plate. This is called subduction. The oceanic plate is partially re-melted.
4.1 Igneous Rocks
Igneous rocks are made when molten rock cools down and solidifies. The slower the molten rock cools, the larger the crystals become. For example, gabbro has larger crystals than basalt because the molten rock that formed gabbro cooled more slowly.
Igneous rocks- Higher tier
Different types of igneous rocks form lava (molten rock on the Earth’s surface):
basalt is rich in iron - it formed from runny lava produced in a fairly safe volcanic eruptionrhyolite is rich in silica - it formed from thick lava produced in an explosive eruption.