ENVI 170 Lecture Notes - Lecture 2: Mariana Trench, Igneous Rock, Asthenosphere
19 Sep 2016
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Document Summary
Validation of seafloor spreading: starts with earth"s magnetic field. Generated by circulation of liquid iron in the outer core. Creates a magnetic field similar to a dipole bar magnet. The poles correspond closely but not exactly with the poles. A compass needle points to the magnetic north pole. Most rocks contain minerals that are naturally magnetic: include iron oxides magnetite and hematite, these rocks act like weak magnets. When basalt, or igneous rock, cools and crystallizes form a liquid, the direction and intensity of the magnetic field when the rock forms is locked permanently into the crystals of these minerals: thermal remnant magnetization. Validation of seafloor spreading: magnetic reversals on seafloor, ocean coring project in the late 1960"s. A hot spot is a stationary area of volcanic activity within the interior of a plate by magma rising: examples of hotspots: The lithosphere (crust and upper mantle) forms a ridged shell.
