Probably, it is difficult to find a person who has never 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, and in the media, there are often references to them. But only a few know about their nature, the danger they bring with them, as well as about the largest faults that can destroy our civilization. Let's talk about it all.
Why faults form
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 simply 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 on each other. It is in these places that the faults of the earth's crust are formed.
In ancient times, when the movement was more active, hills, mountains and entire mountain ranges formed at the places of such joints. Over the pastbillions of years, the processes have become much less noticeable and active. But still, this is quite enough to lead to volcanic eruptions, huge destruction, and the appearance of a tsunami. So learning more about rifts would be very helpful.
Main types of faults
Let's start with classification. Geologists usually divide all faults into three types: shear, dip and normal-slip. Now let's talk about each of them in a little more detail.
First of all, it is worth mentioning the shear - the most common type of faults. Everything is simple here - two lithospheric plates move in a horizontal area relative to each other. Moreover, they can either approach or diverge, or remain at the same distance from each other. In any case, with active movement, the elements can roam in earnest, sweep away entire cities, change the course of rivers and the outlines of continents.
The most dangerous is considered to be a dip-shifted fault. In this case, the movement of two plates occurs in a vertical surface, that is, one plate rises and the other falls. This poses an even greater threat to people and all of nature - we will talk about this below.
If the movement occurs in two planes at once (this also happens, although relatively rarely), a fault is formed, which experts call a fault-shift. After all, on the one hand, the plate throws off the other, but on the other hand, they move apart or shift.
The rift gets its name depending on how it originated. After all, withover time, its orientation may have changed - due to slopes, regional or local folds.
Now let's talk about each category in more detail.
A little about faults with vertical displacement
All such faults are additionally divided into three categories: faults, thrusts and reverse faults. The first can be observed when the earth's crust is stretched, due to which one block (hanging) is lowered in relation to the second (sole). If at the same time a section of the earth's crust is formed, which turned out to be lower in level, then it receives the name of a graben. In the case when the site is raised, it is called a horst.
Mechanically, the rebound is similar to the reset, but in this case, the action happens in reverse. Here the movable layer rises above the sole. In cases where a crack is formed with an angle of 45 degrees or more, it is a reverse fault that appears.
Thrust has much in common with a reverse fault, but only those faults in which the fracture has an angle of less than 45 degrees are called so. As a result of thrusts, folds, rifts and slopes are formed. In addition, klippas and even tectonic covers may appear. The entire plane, on one side of which there is a break, is called the fault plane.
Shifts in brief
Shifts are not as diverse as faults with vertical displacement. Most often, the 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.
It happens when twoThe plates move not in opposite directions, but in the same direction, 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 we will discuss a little later, is a clear example of a transform fault. The consequences of such a displacement 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 faults existing 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 break. The professor studied it for 13 years - from 1895 to 1908. As a result, when a devastating magnitude 7.7 earthquake struck in 1906, Lawson was able to prove that the fault was still active and could subsequently grow, which would particularly affect southern California.
The length of the fault is approximately 1200 kilometers. It is because of him that the area is seismically dangerous. The last strong earthquake occurred here relatively recently - in 1989. Then its power was 7.1 points. But for the last almost thirty years there have been no shocks. However, this is not at alldoes not reassure experts - on the contrary, they believe that if there is no string of small earthquakes, then the next one 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 of large faults in the earth's crust, it is impossible not to talk about the Pacific ring of fire. It is called so not at all by chance - the fault runs almost along the perimeter of the Pacific Ocean. Moreover, it unites 328 out of 540 active volcanoes today. Any little thing (from a geological point of view) can lead to the fact that a massive eruption will begin, followed by a shift of the plate, pressure on the neighboring ones. It's scary to even imagine what consequences this will lead to.
The fault affects a variety of points: the Kuriles, Japan, New Zealand, Antarctica, New Guinea, the Solomon Islands, the Cordillera and the Andes. So, in terms of length, this particular fault can be called the most impressive with confidence.
But the most dangerous point of this ring is Indonesian. Here is a lithospheric plate that acts as the bottom of the Indian Ocean. Gradually, it goes under the Pacific plate. This is what causes terrible cataclysms: tsunamis, earthquakes, volcanic eruptions and other catastrophes that can often be heard in the news.
Another large fault in the earth's crust is located in Central Africa, on the border of Rwanda and Congo. Here is Kivu - one of the largest freshwater lakes in Africa. Itwas the result of the interaction of the Arabian and African tectonic plates. Gradually, the basin of the lake expands. 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 that happened to be nearby were boiled alive.
An additional danger to local residents is the deposits of carbon dioxide and methane located under the lake. If one of the nearby volcanoes fails, the explosion could wipe out up to 2 million people in the Congo and Rwanda.
Alas, some of the largest faults in the earth's crust are in our country. Moreover, each of our compatriots heard about 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 the collision of the Amur Plate with the Philippine and North American that causes so much trouble for Japan.
Earthquakes are quite common here, and sometimes there are volcanic eruptions. According to geologists, in just a few hundred million years, Baikal will become part of the ocean.
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 thisknowledge will greatly expand your stock of knowledge in this area.