Evidence of Plate Tectonics Theory

Notes

Evidence of Plate Tectonics Theory: SEAFLOOR SPREADING 1. When two oceanic plates diverge, new oceanic crust forms at the boundary. 2. Oceanic crust formed on the divergent boundary move laterally outwards on both sides of the boundary. This is known as seafloor spreading. EXPLANATION OF EVIDENCE (2): • Rocks nearest to the divergent boundary are the youngest, and as the rocks get further, they also get progressively older. 3. This results in the formation of chains of mountains on both sides of the boundary, otherwise known as mid-oceanic ridges 4. Little sediments are found at the oceanic trenches as older oceanic crust is destroyed when it subducts under the continental crust. MAGNETIC STRIPING 1. Earth has a magnetic North and South, and has changed multiple times over geologic time. 2. A zebra-like pattern is formed when strips of normal polarity alternates alongside reversed polarity. This gives rise to a symmetrical pattern on both sides of the mid-oceanic ridge. 3. Basaltic rocks from oceanic crust are formed from iron-rich lava, which contain magnetic materials. 4. These materials point towards Earth’s magnetic North, recording the Earth’s polarity at that time.