What is the rate of subduction for the Pacific plate and has it been constant?
Brandon
Cochrane
Hi Brandon,
The subduction rate for the Pacific plate is different depending on where you
are looking. This is because the plates are actually curved (like a broken egg
shell) and are moving across a curved surface (the Earth). The plates are
therefore moving along curved paths (called great circles) rather than in
straight lines. You can demonstrate the idea by swinging a rope around your
body with a weight tied to the end. If the rope is 5 feet long, the weight
travels the circumference of the circle (pi x 2 x 5 = 31.4 feet) each time you
go around. Your hands, however, travel a much shorter distance (maybe 5 feet)
each time around. So, even though they are connected, the weight and your hand
are going at different rates.
The map I have shows the Pacific plate subducting at 6.7 cm/year under New
Zealand, 9.7 cm/year under Tonga, 10.3 cm/year under Japan, and 8.1
cm/year under the Aleutians.
It is kind of a confusing picture, but by looking at a map, it may get
clearer. Keep asking good questions!
Sincerely,
Scott Rowland, University of Hawaii
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