Question

From Hawaii to the bend in the Hawaiian-Emperor chain is about 4000 km. If the Pacific plate is moving 8.0 cm a year, estimate how long ago the direction of plate motion changed. (The San Andreas Fault in southern California became active at about the same time!)

Does anyone have an answer?

Answer 1

This sounds more like geology (or planetary studies) than astronomy.
Presumably the direction of plate motion changed where there is a bend in the chain. So..
Divide 4000*10^3 m by 0.08 m/year.

You get 50 million years.

Answer 2

Thank you!