Man’s knowledge of, and explanation of earthquakes is constantly evolving as more is learned about the earth. A thousand years ago, the commonly accepted explanation ranged from angry gods to great creatures that writhed and churned, causing the temblors. Little changed regarding this view as late as the 19th century. The reason was that nearly all scientists of the time believed that the continents were solid, static and unmoving.
Alfred Wegener’s contribution
Alfred Wegener challenged the view of an unchanging Earth in 1912. Wegener had noticed something that had been noticed before; South America and Africa appeared to fit together like the pieces of a huge jigsaw puzzle. Closer examination showed that geological features on one continent almost exactly matched those on the other, had the two actually been side by side. Based originally on this evidence, Wegener put forth the theory of continental drift. This idea stated that the continents were in fact floating and moving.
At first, the theory wasn’t very well accepted. But science isn’t a democracy, where majority opinion is necessarily the correct one. As scientists trying to disprove the theory of continental drift gathered more and more data, often the theory was supported. Ultimately, the theory of plate tectonics was born.
In the plate tectonics theory, it isn’t just the continents that are moving. Rather, the surface layer of rock on the earth, or the crust, is divided into a number of major plates and a larger number of minor ones. Some of these are purely oceanic, meaning that oceans, which cover 3/4 of the planet, after all, cover them. Other plates consist of both continents and ocean crust. Still, no explanation was found at first for the mechanism for the motion.
Mid oceanic ridge
Then the mid-oceanic ridge was found in the Atlantic Ocean. In this area, the ocean floor is being pushed apart, virtually pushing the Americas away from Africa. There was a time of confusion about this, because though it was a measurable phenomenon, since the size of the earth wasn’t appreciably changing, it meant that if new sea floor was being created, somewhere, somehow, sea floor must be getting destroyed. It was enlightening when such an area was found, in the North Pacific Ocean.
It came to be understood that what actually happens is that one plate slips under another, or is subducted. This went a long way toward explaining earthquakes, as well as explaining why the majority of earthquakes in the world are experienced in the Pacific basin, which has since been dubbed the Ring of Fire, since most active volcanoes also occur there.
Following up on this idea, we now know that plate tectonics are the main, though not only, mechanism for earthquakes. If two plates are moving past each other, they never do so exactly, so they occasionally bind together. Since the plates are still moving, tension builds between the plates until they finally slip as rocks break and release a section of the two plates. The result is an earthquake.
This is not the only type of fault. Sometimes in the release, one portion of rock rises while another falls. In others, one plate slams into the other, causing not only earthquakes, but also the building of often towering mountains. Such was the formation of the Himalayas.
As previously mentioned, this isn’t the only mechanism. Movement of magma underground prior to, during, or just after a volcanic eruption can also cause an earthquake, as rock is broken and melted. Man can also cause earthquakes, by the detonation of explosives or nuclear devices; mining activities, high pressure injection, or even dam building, since the water infiltrates minute faults and serves as a lubricant, allowing the rock to shift.
While we now have a very good idea of what causes earthquakes, though, we are still learning and refining our techniques and knowledge. We still cannot accurately predict quakes, although we can now identify areas that are under enormous amounts of strain. Indeed, we may never be able to predict them. However, considering the progress that has been made since 1912, about a hundred years ago, we just might, too.
We can now explain earthquakes. At this point, it is the more precise information that we lack, and that is what seismologists are currently studying. We can look forward to many new and interesting discoveries in the coming years, and despite the destruction, no longer are earthquakes mysterious things that are based on the whim of mystical beasts or beings.