EES 150 Lecture Notes - Lecture 4: Plate Tectonics, Magnetite, Oceanic Crust
Document Summary
Harry hess started mapping the seafloor while in the navy during wwii. He eventually helped proposed modern theory of plate tectonics. Exploration of ocean led to theory of plate tectonics. The lithosphere consists of rigid plates which move relative to each other. The asthenosphere behaves as a plastics allowing movement of the lithosphere. The crust is composed of plates that moves relative to each other. The mid-ocean ridges are places where plates are moving away from each other. The deep ocean trenches are places where plates are moving towards each other. Paleomagnetism preserves earth"s magnetic field in iron-rich rocks they form. Magnetite is an iron-rich mineral which behaves as a magnet. Magnetite is common in some types of igneous rocks. Magnetite may also be found in sedimentary rocks, where the grains will align with the magnetic field. The principle of superposition states that in layered rocks, the oldest layers are on the bottom.