The Life and Times of a Tectonic Plate

Generally, the ground beneath our feet seems pretty permanent. There are only a few strange and unusual circumstances that put this into doubt, like mudslides and quicksand, which understandably tend to leave people shaken. Even when these phenomena occur, though, the ground is still there, just a bit displaced from its initial location. Can you image the crust disappearing under the ground, out of sight and never to be seen again in this lifetime? As dramatic as that description is, this circumstance is actually happening around the world.

Everyone knows about tectonic plates. Everyone knows about the supercontinent of Pangaea, when all the continents of the world were united as one. Everyone knows that the continents obviously shifted to be in the positions they are in today. Have you ever considered how this happened? The Earth’s crust covers the entire planet; there isn’t any wiggle room for plates to slide past each other. That means that, in order for one plate to move, others need to get out of the way. They do this by pushing one plate under the other, slowly pressing the lower one deep into the interior of the Earth.

Areas where one plate is pushed under another are known as subduction zones. As unfamiliar as the term may be, I can guarantee everyone is familiar with their results. Some of the most scenic and famous volcanoes in the world (Mt. Fuji in Japan, Mt. Rainier in Washington State, Mt. Vesuvius in Italy, the list could go on) are the direct result of subducting plates. This includes all of the volcanoes that make up the infamous Ring of Fire around the Pacific Ocean. These locations also have the potential for the largest earthquakes in the world as the plates slide past each other, and often the potential for devastating tsunamis.

From volcanoes like Mt. Rainier, it is clear that the Pacific Northwest of the United States is located on top of a subduction zone. This particular interaction between plates is special, however. The continent of North America is located on the North American plate (such a creative name). For places like California and Alaska, this plate interacts with the Pacific plate (found under the Pacific Ocean). In the Pacific Northwest, however, this isn’t the case. Instead, there is a different, significantly smaller plate that is causing quite a stir. The Juan de Fuca plate, as it is called, is the last remnant of the ancient Farallon plate, and it is slowly getting smaller. Seismic imaging indicates it is breaking apart as it is pulled down, twisting and tearing inside of the Earth. Perhaps some pieces are breaking free and attaching to other plates. Perhaps that will be the fate of what remains of the plate at the Earth’s surface. Researchers believe it won’t be too long before the Juan de Fuca plate will be no more.

Of course, time is relative. A short time geologically speaking is a long time for humanity. It will be many years before the plate disappears completely. Still, the death of the Juan de Fuca plate offers a great opportunity for understanding how the world has changed over time. The world is constantly being reshaped, and the slow disappearance of a plate gives a glimpse into the forces that have formed the world we know. It’s a rare chance that people are here with enough technology to document what we can of the plate’s ultimate death. It’s a fascinating world we live in, and we’re lucky to be able to watch it.

Images: Cover, 1, 2, 3