It is probably hard to find a person who would never have heard of the breaks in the earth's crust. After all, this issue is briefly studied in the school geography course, and on the Internet, in books, in the media, there are often references to them. But only a few know about their nature, the danger they carry with them, as well as about the largest faults that can destroy our civilization. Let's talk about all this.
Why are faults formed?
The reason for the formation of faults is very simple - the movement of lithospheric plates. Located deep below the surface of the earth, they are in constant motion. Yes, their speed is just miserable - usually from 1 to 10 centimeters during the year. Therefore, people simply do not pay much attention to such a movement. However, even at such a low speed, the plates collide and press against each other. It is in these places that the faults of the earth's crust are formed.
In antiquity, when the movement was more active, in the places of such joints elevations, mountains and entire mountain ranges formed. Over the past billions of years, processes have become much less visible and active. But nevertheless, this is quite enough to lead to the eruption of volcanoes, huge destruction, the appearance of a tsunami. So to learn more about the faults will be very useful.
The main types of faults
Let's start with the classification. Geologists usually divide all faults into three varieties: shear, fall bias , and fault-shear. Now let's talk about each of them in a little more detail.
First of all, it is worth mentioning the shift, the most common type of fault. Everything is simple here - two lithospheric plates move in a horizontal area relative to each other. Moreover, they can both approach or diverge, and remain at the same distance from each other. In any case, with the active movement, the elements can seriously go around, sweep away entire cities, change the course of rivers and the shape of the continents.
The most dangerous is a fault with a shift in the fall. In this case, the movement of two plates occurs in a vertical surface, that is, one plate rises, and the other decreases. This poses an even greater threat to people and the whole nature - we will talk about this a bit below.
If the movement occurs in two planes at once (this also happens, although relatively rarely), a fault forms, which experts call the fault-shift. After all, on the one hand, the plate throws off the other, but on the other, they move apart or move.
The fault gets its name depending on how it originated. Indeed, over time, its orientation could change - under the influence of slopes, regional or local folds.
Now let's talk about each category in more detail.
A bit about vertical offset faults
All such faults are further divided into three categories: faults, thrusts, and thrusts. The first can be observed when the earth's crust is stretched, due to which one block (hanging) falls in relation to the second (sole). If at the same time a plot of the earth's crust is formed, which turns out to be at a lower level, then it is called graben. In the case when the site is elevated, it is called a handful.
In mechanics, the reverse is similar to the reset, but in this case the action occurs as if on the contrary. Here the movable layer rises above the sole. In cases when a crack is formed with an angle of 45 degrees or more, it is a reverse fault.
The thrust has much in common with overthrust, but only those faults in which the crack has an angle of less than 45 degrees are called so. As a result of overthrusts, folds, rifts and slopes are formed. In addition, clips and even tectonic covers may appear. The entire plane, on one side of which the gap passes, is called the fault plane.
Briefly about shifts
Shifts are not as diverse as faults with vertical displacement. Most often, plates simply move relative to each other, rub, forming small irregularities, folds of the earth's surface. But in some cases, this can lead to a transform fault.
This happens when two plates do not move in opposite directions, but in the same, but at different speeds. Most of these faults are located at the bottom of the oceans, but some of them are also on land. For example, the San Andreas Fault, which will be discussed later, is a clear example of a transform fault. The consequences of such a movement can be either unnoticed by people or lead to terrible cataclysms.
San Andreas Fault
If we talk about the largest fault in the earth's crust, then first of all it is worth mentioning San Andreas. It is located at the meeting point of the North American and Pacific lithospheric plates. Thus, it crosses almost the entire western United States - from southwestern Canada to southern Mexico. It is he who is the most dangerous of all existing faults on planet Earth today.
It was first discovered at the end of the nineteenth century by Professor Andrew Lawson. He gave the name to the fault. The professor studied it for 13 years - from 1895 to 1908. As a result, when a terrible earthquake of magnitude 7.7 occurred in 1906, Lawson was able to prove that the fault remains active and could subsequently grow, which will especially affect southern California.
The length of the fault is approximately 1,200 kilometers. It is because of him that this area is seismic hazardous. The last major earthquake occurred here relatively recently - in 1989. Then its power amounted to 7.1 points. But over the past almost thirty years there have been no shocks. However, this does not reassure experts at all - on the contrary, they believe that if there is no string of small earthquakes, then the subsequent will become especially destructive. True, no one can say when it will be - in a week, a year or several decades.
Pacific ring of fire
Speaking about the large faults of the earth's crust, one can not help but talk about the Pacific Ring of Fire. It is called so not by chance at all - the fault runs almost along the perimeter of the Pacific Ocean. Moreover, it combines 328 of the 540 active volcanoes today. Any little thing (from a geological point of view) can lead to the fact that a mass eruption begins, followed by a plate shift, pressure on neighboring ones. It’s scary even to imagine what consequences this will lead to.
The fault affects a variety of points: the Kuril Islands, Japan, New Zealand, Antarctica, New Guinea, the Solomon Islands, Cordillera and the Andes. So in terms of extent, this particular fault can be safely called the most impressive.
But the most dangerous point of this ring is the Indonesian. Here is the lithosphere plate, which acts as the bottom of the Indian Ocean. Gradually, she goes under the Pacific plate. This is precisely the reason for the terrible cataclysms: tsunamis, earthquakes, volcanic eruptions and other disasters, which can often be heard on the news.
Kivu Lake
Another major fault in the earth's crust is located in Central Africa, on the border of Rwanda and the Congo. Here is Kivu - one of the largest freshwater lakes in Africa. It was the result of the interaction of the Arabian and African tectonic plates. Gradually, the basin of the lake is expanding. This leads to a deepening of the reservoir, as well as an increase in volcanic activity in the region. For example, in 1948, the Kituro volcano erupted here. At the same time, in some parts of Lake Kivu, the water simply boiled - the fish, which appeared nearby, was boiled alive.
An additional danger for local residents is the carbon dioxide and methane deposits located under the lake. If one of the nearby volcanoes erupts unsuccessfully, the explosion could destroy up to 2 million residents of the Congo and Rwanda.
Baikal
Alas, some of the largest faults in the earth’s crust are in our country. And each of our compatriots has heard of one of them - this is Lake Baikal. After all, scientists have long proved that it was formed due to the fact that the Amur and Eurasian plates are gradually diverging - the speed is about 4 millimeters per year. By the way, it is precisely the collision of the Amur Plate with the Philippine and North American that causes so many troubles to Japan.
Earthquakes are quite common here, and sometimes volcanic eruptions also occur. According to the forecasts of geologists, after only a few hundred million years, Baikal will become part of the ocean.
Conclusion
This concludes our article. Now you know enough about the deep faults of the earth's crust, their origin, the danger they pose to humanity, as well as the largest of them. Surely this knowledge will significantly expand your stock of knowledge in this area.