Transcript Chapter 17
Chapter 17 Section 2 Seafloor Spreading Technology/Ocean Topography Sonar uses sound waves to measure ocean depth Magnetometer – device that detects small changes in magnetic fields Maps showed underwater mountain chains, ocean ridges, and deep sea trenches. Ocean Rocks and Sediments The ages of rocks in the seafloor vary in different places in a predictable way Oldest part of seafloor = 180 million y/o The thickness of ocean floor sediment is less than expected Age of oceanic crust increases with distance from a ridge; Sediment thickness increases with distance from a ridge Magnetism Earth’s magnetic field is caused by molten iron in the outer core; a compass Describe magnetic reversal The study of plaeomagnetism led to the development of the magnetic polarity time scale The oceans crust is mostly balsaltic rock; form stripes along the ocean floor parallel to ocean ridges Magnetism Isochron maps are imaginary lines ona map that shows points on Earth with the same age. Young crust near ocean ridges and older crust near deep seas trenches Seafloor Spreading Seafloor spreading is the theory that explains how new ocean crust forms at ridges and destroyed at trenches This is Wegener’s missing link in his explanations of continental drift