Exercise_5

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Rutgers University *

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101

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Biology

Date

Jan 9, 2024

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3

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INTRODUCTION TO OCEANOGRAPHY Spring 2022 11:628:120:02/01:460:120:01 Exercise 5- Seafloor Spreading Date Distributed: 10 February 2022 Date Due: 11 February 2021 @ 6p; uploaded into Canvas class website SmallGroupSet2#: 9 Names: Wiliam Kohler, Angela Poulos, Johnny Munoz, Elizabeth Gondek, Samantha Afonso New seafloor is continuously being created along oceanic ridges, where lithospheric plates move apart. The rate at which the plates are moving is similar to the rate at which your hair grows. Remember that to calculate a spreading rate we need two components: time and distance. If we know the age of the crust and the distance from the ridge center, we can calculate how fast the two plates are moving away from each other. Look at the figures of oceanic ridges (spreading centers) illustrated below: 1) Calculate the half-spreading rate across the Mid-Atlantic Ridge and East Pacific Rise. Make sure you give the right units. - Half spreading rate is the rate at which each plate is moving away from the boundary Mid atlantic ridge: 0.03 meters per year (apart) Single sided East pacific rise: 0.06 meters per year 2) What is the full spreading rate of the same ridges? This is the rate at which ocean basins are opening. - The full spreading rate is the rate at which the plates are moving away from each other, the full rate of spreading Mid Atlantic Ridge: 0.06 meters per year East Pacific Rise: 0.12 meters per year
The map below shows a portion of the North Atlantic Ocean, with the Mid-Atlantic Ridge highlighted in the center. Dashed lines parallel to the ridge show the age of seafloor basalt in millions of years (My), as derived from magnetic polarity reversal. 3) Is the ocean expanding or contracting? What is the evidence? The ocean looks like it is expanding because you can see the older layers are spread out near the North American and African plate boundaries. This means that the floor is expanding outwards towards the continents, away from the ridge. The older the seafloor, the further away it would be from the ridge, where new seafloor is being formed. The ridge also signifies a divergent plate boundary here which means spreading of the plates at this spreading center and the expansion of the ocean through the creation of new crust at the spreading center 4) Complete the table for the locations marked with a letter: Location Distance from Ridge (km) Age of Seafloor (My) Rate of Movement (km/Myr) A 350 35 millions of years 10 km/Myr B 800 84 millions of years 9.52 km/Myr C 1400 118 millions of years 11.86 km/Myr D 1900 156 millions of years 12.18 km/Myr E 1700 156 millions of years 10.90 km/Myr 5) At what rate is Africa moving away from or heading toward North America?
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