Fastest Moving Islands

By Rick Schleicher

Join the most unique creatures in the world for a thrill ride on the fastest moving islands on the planet!

Four inches a year! That’s hell bent for leather, speed of light kind of stuff for land masses.

If you are here for ten days, these islands will have moved out from under your feet by one tenth of an inch. They have moved more than six feet since I’ve been here. You really kinda gotta hang on for fear of slipping off. Not only are they the fastest moving islands on the planet, they are the fastest growing, fastest shrinking and fastest sinking. Rather than having an SUV parked in their driveway, the more forward thinking people on my block have boats.

To understand this phenomenon you need a degree in paranoid psychology and the knowledge that we use boats far more often than SUV’s, also no-one actually has a driveway.

Let me start again, to understand this natural phenomenon requires a very rudimentary grasp of earth sciences. It is not as fun as dining with sea lions and giant tortoises, but it will help you understand how they managed to get to your reservation on time.

You’ve probably heard that at the center of the earth there are not a bunch of American people digging away trying to get to China; there is the “core” of this huge pool of melted rock called magma and over this very hot pool of magma is what they call the earth’s mantle.

This non-melted rock is 1,800 miles thick. On top of that is what they call the earth’s crust, this is tectonic plates covered in oceans, mountains, etc. Sometimes the magma finds a wee little seep-hole through the mantle, makes it up to the crust, penetrates a tectonic plate or more often comes up between two tectonic plates and viola, we have a volcano, most of which show up first undersea.

Pompeii, Krakatoa, Hawaii are all other examples of places where the wee little seep-hole is so hot it penetrates a tectonic plate, continuing to penetrate as the plate moves. It is not really so much of a “hot spot” as it is called as it is a hot knife to the butter of the tectonic plate which is just doing its thing, moving in a direction. This is where it gets interesting. The magma makes it up through the plate and into the sea or atmosphere and then what? It doesn’t evaporate. That’s a bunch of liquid rock. It just falls over on its sides, cools, hardens and rides the tectonic plate as it moves away from the hot spot. It piles up. In the case of the Galapagos it piles up from 10,000 feet below sea level. This is important to remember. The western edge of the Galapagos descends to 10,000 feet below sea level.  It’s like an underwater 10,000 foot cliff. The eastern side where all the magma has piled up and moved on, at its deepest is 3,000 feet.

All tectonic plates are not created equal. The Nazca plate on which the Galapagos sits is moving west to east, the fastest moving plate on the planet, has run into the South American plate and is “subducting” below it. One of the results of which has been the Andes mountains. This has been going on for so long that volcanic rocks formed in the Galapagos have been found in Venezuela. Think about that! The Nazca plate is diving below the South America plate which forces it to sink along with the islands on it.

The Galapagos islands which have moved off the “hot spot” not only have the natural forces of erosion working on them while they are no longer growing, but the base they sit on is going under water at the rate of approximately one half inch a year, hence the need for some of my more forward thinking of buddies to keep boats in the driveway.

Sierra Negra Volcano

Let us take the Island of Isabela as an example. This is the largest of the Galapagos islands, the second youngest of the islands, approximately a million years old, and still has four active volcanoes. When you fly in, you will see the volcanoes which create the highlands and are verdant green with flora, unless there has been a recent lava flow and below that surrounding them are miles wide, nearly flat, practically barren hardened lava flows. There might be a random group of cactuses flourishing or a small fishing village turned tourist destination with the airport you are about to land in.

San Cristobal is one of the older islands, approximately three million years old and has no active volcanoes and none of these coastal lava fields. Why? It does have those coastal lava fields, they are just underwater now. Isn’t that fun?

So, say you got a volcano, volcano Wolf on Isabela for example, that starts 10,000 feet below sea level and then peaks up above the ocean another 5,600 feet. The area of the volcano above sea level on a map is 3,040 square miles when measured from above so we can give an average width of the conical volcano of approximately 62.2 miles at sea level. That means the part of the volcano above sea level has a volume of 1,012.86 cubic miles. If you think that is weird, try this one; a cubic foot of volcanic rock weighs about 25 pounds so the weight of the volcano above sea level is 3.7 quadrillion pounds! (Geometric Calculations provided by much wiser men than me)

We don’t often think in terms of cubic miles, but try it. Think of just one cubic mile of rock and then multiply that by 1,012.86. Isn’t that fun?

Here’s the other fun part, active volcanoes are really hot, even the land around them is relatively hot.

Everyone knows matter expands when it is hot and contracts when it is cold, with a couple of exceptions, water being one. So, we have this huge volume of hot to warm rock that cools as it rides the tectonic plate moving off the source of that heat. The average temperature of the earth’s crust is 56 degrees. Let’s say you have a cubic mile of volcanic rock at let’s say an average temperature of 72 degrees. At 56 degrees it will be 6.88% smaller. The islands shrink as they move off the hot spot by 6.88%!

And there you have the fastest growing, sinking and shrinking islands on the planet. I know what your next question is, how much will the islands shrink if you are on them for ten days?

But here’s the really fun part, all of the above accounts for why Galapagos giant tortoises live as long as they do – and that’s for next month’s story!