As a lithospheric plate moves over a hotspot in the upper mantle below the plate, avolcano develops directly above the hot spot. 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 over the hot spot 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 hot spot.
A Figure2.13 shows the distribution of the Hawaiian Islands chain and Emperor Seamount Chain. The numbers indicate the average age of the volcano in millions of years(Myr) obtained from isotopic dating of the basaltic igneous rock of which each island is composed.
1， If both the emperor and Hawaiian Islands chains developed as a result of the same mantle hotspot, what is a possible reason that 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 2300km long Emperor Seamount Chain from 65 Myr to 42Myr? Express the rate in centimeters per year(cm/yr.).In what direction was the plate moving north-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 cm/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 0.8Myr to today, expressed in cm/yr?
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