Activity 2. Seafloor spreading One of the key points proving plate tectonic theory was the validation of seafloor spread

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Activity 2 Seafloor Spreading One Of The Key Points Proving Plate Tectonic Theory Was The Validation Of Seafloor Spread 1 (150.11 KiB) Viewed 117 times

Activity 2 Seafloor Spreading One Of The Key Points Proving Plate Tectonic Theory Was The Validation Of Seafloor Spread 2 (149.81 KiB) Viewed 117 times

Activity 2. Seafloor spreading One of the key points proving plate tectonic theory was the validation of seafloor spreading by looking at the age of the seafloor. Early validations had to drill the seafloor in discrete locations and use radiometric dating to get an age of the underlying crust. Today we can use magnetic reversals on the seafloor to get very precise ages for the rest of the seafloor without the need for expensive drilling along the entire ocean. We can use this information to determine how seafloor-spreading rates have changed over the past millions of years. Below is a greatly over simplified map showing the age of the seafloor in the North Atlantic (Figure 2). Use it to answer the following questions. 0 Holocene & Pliocone 5.3 Spain North America .D Miocane, Oligocene, Eocens, & Paleocone Late Cretaceous ●G C Lower Cretaceous Africa Jurmasic Kilometers 0 500 1000 1500 2000 South America Figure 2. Map of seafloor ages in the North Atlantic. ©2015 Pearson Education, Inc. 1. Using a ruler and the scale bar in the lower right of the map, in kilometers, how far apart are points B and C? 0200052 tane 2. Assuming that 145 million years ago B and C were at the same location at the ocean ridge, how fast has the North Atlantic been spreading for the last 145 million years (in kilometers/million years)? Make sure you keep track of your units. 3. In kilometers, how far apart are points F and G? Seafloor Ages in Millions of Years Ago (M) 66 100 145
4. Assuming that 66 million years ago F and G were at the same location at the ocean ridge, how fast has the North Atlantic been spreading for the last 66 million years (in kilometers/million years)? 5. Given the spreading rates calculated in questions 2 and 4, has the Atlantic been spreading faster or slower over the last 66 million years compared the previous 145 million years? 6. Convert your answer for question 4 from kilometers/million years to millimeters/year. (hint, there are a million millimeters in a kilometer) 7. Given the above calculation (question 6), how much further is the New World from Spain today than it was when Columbus first arrived in 1492 (How far has the Atlantic opened since then)? How much further since American troops had to travel to Normandy in 1944? Give your answers in meters. Activity 3. GPS validation of plate tectonics Ever wonder how you phone finds where you are? In its high-resolution mode, it is utilizing the GPS system. The GPS (Global Positioning Satellite) System is a collection of about 30 satellites that are geosynchronously locked to a specific location over the Earth. Because they are in geosynchronous orbit, they are orbiting the planet at the speed of planetary rotation, and are always located over the same spot. Once your phone locates 4 satellites, it can calculate its exact location on the planet.