plate tectonics

• The Earth is estimated to be 4.6 billion years old and formed from the aggregation of materials thrown out by the explosion of a star in the Big Bang.
• The Earth started as a ball of molten materials that slowly cooled to form a crust of solidified rocks.
• Volcanic activity released gases from the Earth's interior, forming a primitive atmosphere.
• The early Earth experienced frequent asteroid impacts and was not conducive to life.
• The oldest known rocks on Earth are generally dated between 2.5 and 3.8 billion years.
• Rocks in North West Iceland are 16 million years old, with some older volcanic rocks dating back up to 37 million years.
• The oldest rocks in the British Isles, found in North West Scotland, are more than half as old as the planet.
• Human beings arrived on the geological scene around 2.3-2.4 million years ago in Africa.
• Tectonics is a theory that explains the structure and composition of the Earth.
• The Earth is believed to have formed approximately 4.5 billion years ago.
• The Earth's crust is made up of rocks known as the Lithosphere.
• The Lithosphere is divided into large segments called Tectonic plates.
• Tectonic plates move slowly due to convection currents in the mantle.
• The mantle is a zone of molten Silicates and other minerals.
• The boundary between the crust and mantle is known as the asthenosphere or Mohorovicic discontinuity.
• The Earth has a solid core of Iron and Nickel, which is solid due to intense pressure.
• There is a transition zone between the outer core and mantle.
• The evidence for the Gutenburg Discontinuity comes from different seismic waves and their travel through the Earth.
• P waves are the fastest waves, arriving first at recording stations and can travel through both liquids and solids.
• S waves arrive later than P waves and travel at roughly half their speed, shaking the ground from side to side.
• S waves are unable to travel through liquids.
• L waves are restricted to the surface and travel even slower than S waves, arriving last at recording stations.
• There are 2 types of L waves, Love waves vibrate at right angles to the direction of movement but have no vertical movement, while Rayleigh waves have
• P and S waves are seismic waves that travel through the Earth's interior and can be recorded on seismographs.
• P and S waves travel at different rates depending on the material they are traveling through, and S waves cannot pass through liquids.
• Seismographs can be used to determine the material the waves have traveled through, as S waves do not arrive when they have passed through liquid.
• The molten mantle has been detected because S waves do not pass through it, indicating the presence of liquid.
• The Asthenosphere or Moho Discontinuity is a zone with around 10% molten material, where both S and P waves slow down.
• Scientists have used information from seismometers to identify three conventional divisions of the Earth's interior: crust, mantle, and core.
• The Earth's crust is divided into tectonic plates.
• The major plates include the Pacific, Eurasian, African, Antarctic, North American, South American, and Indo-Australian.
• There are smaller plates such as the Philippines and Cocos plates.
• Continental crust is thicker, older, and lighter than oceanic crust.
• Continental crust is composed mainly of granite and is more complex in structure and origin.
• Continental crust is formed primarily at subduction zones at destructive plate margins.
• Continental crust is over 1,500 million years old.
• Oceanic crust is mainly composed of basalt and gabbro, which contain silica and magnesium (SiMa).
• Oceanic crust is younger and heavier compared to continental crust.
• It is formed at constructive margins or spreading mid-ocean ridges and tends to be between 6 and 10 km thick.
• Oceanic crust is constantly destroyed and recreated due to processes at ocean ridges and destructive plate margins.