Structure of the Earth
-The earth is almst spherical, diameter= 12800 km. At the surface there is a thin solid crust, which vaies in thickness between 5km and 70km.
-There is the mantle under the crust and is about 3000km thick, it goes almost halfway to the centre of the earth and is almost entirely solid but can flow very slowly.
-The core is half the diametre of the earth and has a high proportion of manetic metals i.e. iron and nickel. It has a liquid outer part and solid inner.
-The atmosphere surrounds the eath, more of the air is within 10km of the surgace and most of the atmosphere is within 100km of the surface.
-All of the raw materials and other resources that we depend on come from the crust, the oceans and the atmosphere meaning the resources available to us are limited.
The Restless Earth
-Scientists now believe the earths curst and upper part of the mantel is cracked in large pieces called tectonic plates which move a few cm every year because of convection currents in the mantle beneath them, the convection currents are caused by energy released by the decay of radioactive elements heating up the mantle.
-Where pkanets meet huge forces build up, eventually the rocks give way changing shape or moving suddenly causing earthquakes, volcanoes or mountains to form. Scientists do not know enough yet to predict when earthquakes or volcanic eruptions will occur.
-Alfred Wegener pt forward the idea of continental drift in 1915, other scientists at the time didnt accept his ideas because they couldnt explain why the continents moved. They believed the earth was shrinking as it cooled, then in the 1960s scientists found new evidence and the theory of the plate tectonics was developed.
The Earths Atmosphere in the Past
-Scientists think that the earth was formed 4.5 billion years ago, in the first billion years the surface was covered with volcanoes that released carbon dioxide, water vapour and nitrogen.
-As the earth cooled most of the water vapour condensed to form the oceans, so the…