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Structure of the Earth 1. The structure of the Earth consists of; a) a thin crust b) a mantle (solid, but can flow slowly) c) a liquid outer core (made from nickel and iron) d) and a solid inner core (again, made from nickel and iron). Structure of the Earth Seismic Waves 1. The structure of the Earth is known because of the way shockwaves from earthquakes (seismic waves) travel through it. 2. These waves are detected using seismographs. Seismic Waves P-Waves S-Waves Continental Drift 1. The theory of continental drift suggests that they were the continents were once joined together and have since split and moved apart. 2. Continents (e.g. Africa and South America) have shapes that fit closely together and have similar patterns of rocks and fossils Continental Drift Continental Drift Tectonic Plates 1. The lithosphere (crust and upper mantle) is cracked into a number of large pieces (tectonic plates). 2. Convection currents caused by radioactive decay is responsible for these plates moving. Constructive Plate Boundary Plate boundaries Tectonic plates can • slide past each other (conservative plate boundary) • move towards each other (destructive plate boundary) • move away from each other (constructive plate boundary) Constructive Plate Boundary Constructive Plate Boundary Destructive Plate Boundary Destructive Plate Boundary Conservative Plate Boundary Mountain formation