November 19, 2019

That Hawai’ian trip, 82 million years ago

By Jeffrey the Barak.

Let’s say you are hanging out near Hilo on the big island of Hawai’i and wondering what was going on in the neighborhood, oh let’s say, 82 million years ago.

Well if you had a time machine and went back 82 million years or so, you might find yourself in a similar looking spot, on a similar looking island, at the same latitude and longitude, and almost right over the same hot spot, which has not moved at all.

But the island you would be standing on, has moved, and moved far. It still exists today in the dark, cold depths of the North, only we now call it the Meiji Seamount. It is currently the oldest seamount in the Hawaiian-Emperor seamount chain, and in a few more million years, it will have subducted back into the mantle via the bottom of the Kuril-Kamchatka Trench.

If you, the time traveller, were standing on it when it was still Hawai’i, there would likely have been, as there are today, more islands to your North, becoming smaller and smaller along the way, then atolls, then seamounts, and eventually an old submarine island about to subduct. All of these Northern neighbors have since disappeared back into the mantle.

This is assuming the hotspot has always been there since the re-formation of Earth after the planetary collision between Gaia and Theta that formed our current Earth-Moon partnership around 4.5 billion years ago.

The history of Hawai’i is written on the surface of the Earth, underwater, in the form of the Hawaiian-Emperor seamount chain. The Pacific Plate moved north for while, then about 47 million years ago it started to move North-West, forming the bend in the chain that we see on our maps today.

If you ever have an opportunity to look upon a lava lake, you will see a miniature model of plate tectonics, as pieces of crust move around and eventually subduct back into the molten rock. It is a high speed vision of our Earth’s continental plates.

When Meiji was in the current location of Hawai’i, during the Cretaceous period, today’s continents had already started to break away from the one giant supercontinent Pangaea, and Hawai’i was almost completely alone on the other side of the world, even more isolated than it is today, and far from the dinosaurs that were thriving half a world away.

It is unlikely that Meiji is the oldest player in this long, slow story, and we already know that Hawai’i Island will not be the last.

For a timescale reference, bear in mind that Modern humans emerged in Africa only about 200,000 years ago. At that time, 200,000 years ago, the ocean had already flooded in to form channels in sinking Maui Nui, which already looked much like today’s four islands of Maui, Kaho’olawe, Lana’i and Molokai. Hawai’i Island’s Kilauea, however, probably did not break the ocean’s surface until about 100,000 years ago, although it likely emerged from the sea floor around 600,000 to 300,000 years ago. On these timescales, we can say humans found Hawai’i, about a second ago, although it was actually anywhere between 1,500 and 800 years ago. At that time, the island chain was geologically practically identical to how it is today, however humans irreversibly changed the fauna and flora very quickly.

Jeffrey the Barak sees different things when he looks in the same place you look. Sometimes he makes odd sounds.

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