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Transcript
Name: Student Number: Hotspot island chains like the Hawaiian Islands have been used to estimate the motion of tectonic plates over time. The idea is that a hotspot (the source of heat for the volcanoes) is “fixed” in the mantle and a tectonic plate moves over it, producing a linear chain of volcanoes over time. But are hotspots fixed? Can they move? How could we tell? ACTIVITY 1: Assuming the fixed-hotspot-moving-plate model is correct… 1. TOWARD which compass direction was the Pacific Plate moving during the time period about 45 Ma to the present (45 Ma is about where the “elbow” occurs)? (Draw arrow on map too) 2. TOWARD which compass direction was the Pacific Plate moving during the time period ~81-45 Ma? (Draw arrow on map too) Name: Student Number: ACTIVITY 2: TESTING the fixed-hotspot-moving-plate model using magnetic inclination… Seamount Age (Ma) Inclination (º) 78 Ma 61 Ma 56 Ma 49 Ma 0 Ma 60 45 44 38 34 Detroit Suiko Nintoku Koko Hawaii Paleolatitude (latitude of formation) (º) Corals? No No No Yes Yes Data are from Tarduno et al., Science, vol 301, p 1064-1069, 2003. Use Figure 1 below to determine the latitude of formation of the rocks recovered from these different parts of the Hawaii-Emperor Seamount Chain, based on the measured inclination values from the rocks (above, in the table). Inclination versus Latitude Paleolatitude versus Age 45 90 80 35 60 50 30 40 30 25 Paleolatitude (degrees) Inclination (degrees) 40 70 20 20 10 0 15 0 10 20 30 40 50 60 70 80 90 Latitude (degrees) Figure 1: Magnetic inclination versus latitude. 80 70 60 50 40 30 20 10 0 Age (Ma) Figure 2: Paleolatitude versus age On Figure 2, plot your paleolatitude (latitude of formation at some time in the past) versus age of these rocks in the Hawaii-Emperor Chain. Connect the dots. 1. BASED ON THE MAGNETIC INCLINATION DATA, WHAT HAPPENED? (WHAT’S MOVING? The PLATE? The HOTSPOT? BOTH? MAYBE DIFFERENT PLAYERS AT DIFFERENT TIMES????) 2. Do the coral data support your interpretation or not? Explain your reasoning