Structure Of The Earth Monday, May 04, 2015 To know the structure of the Earth
Earth What is the structure of the Earth like?
Earth The Earth is almost a sphere, consisting of four main layers… Crust – relatively thin and rocky Mantle – has the properties of a solid, but can flow very slowly Outer core – made from liquid nickel and iron Inner core – made from solid nickel and iron A thin crust – 10-100km thick A mantle – has the properties of a solid but it can also flow A core – made of molten nickel and iron. Outer part is liquid and inner part is solid The average density of the Earth is much higher than the crust, meaning the inner core must be very dense – solid nickel and iron
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)
Plate Tectonics Why does the Earth look the way it does – has it always looked this way and will it remain?
Plate Tectonics Why does the Earth look the way it does – has it always looked this way and will it remain? The Earth's crust and upper part of the mantle are broken into large pieces called tectonic plates – these are constantly moving at a few centimetres each year Although this rate is not great, over millions of years the movement allows whole continents to shift thousands of kilometres apart – called continental drift The plates move because of convection currents in the Earth's mantle, driven by the heat produced by the decay of radioactive elements and heat left over from the formation of the Earth
Plate Tectonics Where tectonic plates meet, the Earth's crust becomes unstable as the plates push against each other, or ride under or over each other Earthquakes and volcanic eruptions happen at the boundaries between plates, and the crust may ‘crumple’ to form mountain ranges
Alfred Wegener The theory of plate tectonics and continental drift were proposed at the beginning of the last century by a German scientist, Alfred Wegener Before his time it was believed that the planet's features, such as mountains, were caused by the crust shrinking as the Earth cooled after it was formed It took more than 50 years for Wegener’s theory to be accepted because it was difficult to work out what the mechanism was that could make whole continents move, and it was not until the 1960s that enough evidence was discovered to support the theory fully
Tectonic Theory Alfred Wegener suggested that the continents looked like they ‘fit’ together He also noted they have similar rock patterns and fossil records – these two pieces of evidence led him to believe that there was once a single land mass, and form the tectonic theory The massive amounts of heat generated through radioactive decay in the core power convection currents in the mantle causing the crust to move, as well as the spreading of the sea floor at plate boundaries as new crust is formed – both key discoveries and proof of Wegener’s theory
Evidence Plate tectonics explained why earthquakes and volcanoes were concentrated in specific places - around the boundaries of moving plates The match in shape between the east coast of South America and the west coast of Africa suggests both were once part of a single continent There are similar patterns of rocks and similar fossils on both sides of the Atlantic - including the fossil remains of land animals that would have been unable to swim across an ocean
Pangaea Pangaea – the original super-continent is thought to have broken up in the following manner… Earth around 200 million years ago, at the time of Pangaea The single landmass began to crack and divide, due to the convection currents of the magma beneath Current continental positions
Crust Complete the structure of the Earth worksheet…
Crust The Earth’s lithosphere (crust) is split up into different sections called tectonic plates, which are moving apart from each other a few centimetres every year due to the convection currents in the mantle caused by the radioactive decay of rocks inside the core