EVSC 2800 Study Guide - Final Guide: Peridotite, Seafloor Spreading, Dunite
12 May 2016
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Document Summary
Magnetism occurs (most often) when there is an imbalance in the structural arrangement of the iron ions. Iron is found in fe3+ and fe2+ ionic states. Shen the different ions are located in separate positions in a crystal structure, electrons moving from fe2+ to higher positively fe3+ create a slight magnetic field. Mixed oxidation state minerals are magnetite and pyrrhotite. When magma or lava cools, magnetic minerals solidify with their crystals oriented north, along the magnetic field. Earth"s magnetic field in the past was sometimes the reverse polarity of the present field. Epochs of magnetic dominance last about . 5 million years with some shorter transient reversals. An underwater chart was published by u. s. navy lieutenant matthew maury revealed the first evidence of underwater mountains in the central atlantic ocean. The mid-ocean ridge is taller than all of the mountains in north america except. Magnetic surveys were completed by ships crossing the ocean.
