100%(3)3 out of 3 people found this document helpful
This preview shows page 1 - 3 out of 5 pages.
Understanding Planet Earth Final ReviewQuestion 1: Paleomagnetism and Geomagnetic Pole PathsPaleomagnetism– study of earths magnetic fields in rocksoWhen Igneous rocks (lava flows) form they become weakly magnetized as they cool. Direction of magnetism preserves a “fossil” record of earths magnetism at current timeoUsing this evidence, scientists have determined the pole wanders, and even switches magnetism over timeMagnetic orientation of old rocks does not match what it should be were they formed in that spot todayThis discovery served as a large factor in legitimizing the theory of continental drift. Question 2: The Juan de Fuca Ridge and PlateLocated off the coast of Washington and BCJuan de Fuca plate is between North American Plate and Pacific PlateoJuan de Fuca Ridge is divergent boundary (mid-ocean ridge) between Pacific plate and Juan de Fuca PlateoJuan de Fuca PLATE goes under North American plate (@ cascadia subduction zone)Has all three types of plate boundaries in close proximityMoving 2-3 cm / yearCascadia subduction zoneoConvergent plate boundary stretching from North Vancouver Island to Northern CaliforniaoSeparates the Juan de Fuca and North American platesoDenser ocean plate is subducting under Continental plateoEarthquakes and stratovolcanoesSan andreas faultoTransform faultosliding along each other. The majority of this kind of fault are found in the ocean,however the few that are on land pose a huge risk because they cause shallow focus earthquakes, which result in more damage on the surface than comparabledeeper focus earthquakes
Question 3: Age of Oceanic Crustal RocksAnomalies in the paleomagnetic record are stripes showing movementoCaused by geomagnetic reversaloUse these stripes to date the platesRadioactive decay measurements are used to confirm thisUse the GPS system to detect changes in the distance across oceans, which shows us that they are changing every yearSee that rock along the mid ocean ridges is very young, and we can see that rock in the ocean floor is overall quite youngoThis is because the old rock gets subducted under continental plates as it gets pushed out by new igneous rock being formed along the mid ocean ridge.