One Cool Hotspot

Okay, wanna see something really cool? (Actually, it’s kinda hot …)

Below is a cropped image from a 1969 National Geographic map of the seafloor, showing the Pacific basin. What’s the cool part? See that long, almost L-shaped line of ridges and seamounts and islands that has Hawaii at the very end? That’s where the Pacific Plate has slowly moved over a hotspot in the earth’s mantle, which causes seamounts to form, and, occasionally, islands like Midway or Hawaii.

Pacific Floor Ocean Map, National Geographic, 1969.

The ridges show the movement of the Pacific plate over the last 75,000,000 years. Kind of slow movement, only about 6,000 km in that time, or 0.000000009132 km/h, about 80 mm/year.

That bend in the L is where the Pacific plate shifted direction 43,000,000 years ago.

In case you’re wondering where it goes as it moves, you can see the trenches on the top and left edges of the plate. Those are subduction zones, including the Marianas Trench, the deepest part of the ocean on earth. That’s where the Pacific plate is moving underneath the other plates, getting recycled very, very slowly.