How does the current motion of HNLC on Oahu compare to the direction of Pacific Plate motion relative to the Hawaiian hotspot over the past 42 million years?

Lab 2 Tectonic Plates

Hotspots and Plate Motions Activity 2.4 Name’ Learning GOAL You will learn how the volcanic trail left on a plate by a mantle hotspot can be interpreted to tell us where and how fast the plates are moving relative to Earth’s deep mantle. As a lithospheric plate moves over a hotspot in the upper mantle below the plate, a volcano develops directly above the hotspot. As the plate continues to move, the volcano drifts away from the hotspot and eventually becomes dormant. Meanwhile, a new volcano develops over the hotspot next to the older volcano. The result is a trail of volcanoes with one end of the line located over the hotspot and quite active, and the other end distant and inactive. In between is a succession of volcanoes that are progressively older with distance from the hotspot. geFigure 2.13 shows the distribution of the Hawaiian Islands Chain and Emperor Seamount Chain. The numbers indicate the aver-age age of the volcano in millions of years (Myr), obtained from isotopic dating of the basaltic igneous rock of which each island is composed.
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1. If both the Emperor and Hawaiian Islands Chains developed as a result of the same mantle hotspot, what is a possible reason that the hotspot trail changes direction at —42 Myr?

2. What was the rate of Pacific Plate motion relative to the Hawaiian hotspot as it was developing the 2,300 km-long Emperor Seamount Chain from 65 Myr to 42 Myr? Express the rate in millimeters per year (mm/yr). In what direction was the plate moving (north-northwest or south-southeast) relative to the hotspot during that time interval?

3. What was the rate of Pacific Plate motion relative to the Hawaiian hotspot from 5.1 to 0.8 Myr, expressed in mm/year?

4. Using Lo’ihi Seamount as the current location of the Hawaiian hotspot, what was the rate of Pacific Plate motion relative to the Hawaiian hotspot from 0.8 Myr to today, expressed in mm/yr?

5. Go to the JPL-NASA GNSS Time Series website at https://sideshow.jp1nasa.gov/Post/series.html. The map locates each GPS station with a green dot and a yellow line that extends outward in the direction that the GPS station is moving relative to the NNR reference frame. GPS station HNLC is located on Oahu.

How does the current motion of HNLC on Oahu compare to the direction of Pacific Plate motion relative to the Hawaiian hotspot over the past 42 million years?

GPS station HNLC on Oahu has the following component velocities relative to the NNR reference frame as of March 5, 2019: moving north at 34.607 ± 0.038 mm/yr and moving west at 62.814 ± 0.041 mm/year. Use the Pythagorean Theorem to find the current speed of the Pacific Plate at Oahu relative to the NNR reference frame. Show your work.

6. REFLECT & DISCUSS Based on all of your previous work, explain how the direction and rate of Pacific Plate movement changed over the past —70 million years.