Causes of tectonic activity of the lithosphere. Lithosphere and Earth's crust. Plate tectonics as a system of sciences
Then surely you would like to know what are lithospheric plates.
So, lithospheric plates are huge blocks into which the solid surface layer of the earth is divided. Given the fact that the rocks beneath them are melted, the plates move slowly, at a speed of 1 to 10 centimeters per year.
Today there are 13 largest lithospheric plates that cover 90% of the earth's surface.
The largest lithospheric plates:
- australian plate- 47,000,000 km²
- Antarctic Plate- 60,900,000 km²
- Arabian subcontinent- 5,000,000 km²
- African plate- 61,300,000 km²
- Eurasian plate- 67,800,000 km²
- Hindustan plate- 11,900,000 km²
- Coconut Plate - 2,900,000 km²
- Nazca Plate - 15,600,000 km²
- Pacific Plate- 103,300,000 km²
- North American Plate- 75,900,000 km²
- Somali plate- 16,700,000 km²
- South American Plate- 43,600,000 km²
- Philippine plate- 5,500,000 km²
It must be said that there Earth's crust continental and oceanic. Some plates are composed entirely of one type of crust (such as the Pacific Plate), and some are of mixed types, where the plate begins in the ocean and smoothly transitions to the continent. The thickness of these layers is 70-100 kilometers.
Lithospheric plates float on the surface of a partially molten layer of the earth - the mantle. When the plates move apart, liquid rock called magma fills the cracks between them. When magma solidifies, it forms new crystalline rocks. We will talk about magma in more detail in the article on volcanoes.
Map of lithospheric plates
The largest lithospheric plates (13 pcs.)At the beginning of the 20th century, the American F.B. Taylor and the German Alfred Wegener simultaneously came to the conclusion that the location of the continents is slowly changing. By the way, this is exactly what, to a large extent, is. But scientists could not explain how this happens until the 60s of the twentieth century, when the doctrine of geological processes on the seabed was developed.
Map of the location of lithospheric plates It was the fossils that played here leading role. On different continents, fossilized remains of animals were found that clearly could not swim across the ocean. This led to the assumption that once all the continents were connected and animals calmly passed between them.
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Lithospheric plates- large rigid blocks of the Earth's lithosphere, limited by seismically and tectonically active fault zones.
The plates, as a rule, are separated by deep faults and move along the viscous layer of the mantle relative to each other at a rate of 2-3 cm per year. Where continental plates collide, they form mountain belts . When the continental and oceanic plates interact, the plate with the oceanic crust moves under the plate with the continental crust, resulting in the formation of deep-sea trenches and island arcs.
The movement of lithospheric plates is associated with the movement of matter in the mantle. IN separate parts mantle there are powerful flows of heat and matter rising from its depths to the surface of the planet.
Over 90% of the Earth's surface is covered 13 the largest lithospheric plates.
Rift– a huge fracture in the earth's crust, formed during its horizontal stretching (i.e., where the flows of heat and matter diverge). In the rifts there is an outpouring of magma, new faults, horsts, grabens appear. Mid-ocean ridges are forming.
First continental drift hypothesis (i.e. the horizontal movement of the earth's crust) put forward at the beginning of the twentieth century A. Wegener. On its basis, created theory of lithospheric plates m. According to this theory, the lithosphere is not a monolith, but consists of large and small plates, "floating" on the asthenosphere. The boundary regions between lithospheric plates are called seismic belts - these are the most "restless" areas of the planet.
The earth's crust is divided into stable (platforms) and mobile sections (folded areas - geosynclines).
- powerful underwater mountain structures within the ocean floor, most often occupying a middle position. Near mid-ocean ridges, lithospheric plates move apart and young basalt oceanic crust appears. The process is accompanied by intense volcanism and high seismicity.
Continental rift zones are, for example, the East African rift system, the Baikal rift system. Rifts, like mid-ocean ridges, are characterized by seismic activity and volcanism.
Plate tectonics- a hypothesis suggesting that the lithosphere is divided into large plates that move along the mantle in a horizontal direction. Near mid-ocean ridges, lithospheric plates move apart and build up due to matter rising from the bowels of the Earth; in deep-sea trenches, one plate moves under another and is absorbed by the mantle. In places where plates collide, folded structures are formed.
There are two types of lithosphere. The oceanic lithosphere has an oceanic crust about 6 km thick. It is mostly covered by the sea. The continental lithosphere is covered by a continental crust with a thickness of 35 to 70 km. For the most part, this bark protrudes above, forming land.
Plates
Rocks and minerals
moving plates
The plates of the earth's crust are constantly moving in different directions, albeit very slowly. The average speed of their movement is 5 cm per year. Your nails grow at about the same rate. Since all the plates are tightly adjacent to each other, the movement of any of them acts on the surrounding plates, causing them to gradually move. The plates can move in different ways, which can be seen at their boundaries, but the reasons that cause the movement of the plates are still unknown to scientists. Apparently, this process may have neither beginning nor end. Nevertheless, some theories argue that one type of plate movement can be, so to speak, "primary", and from it all other plates are already set in motion.
One type of plate movement is the "diving" of one plate under another. Some scholars believe that it is this type of movement that causes all other plate movements. At some boundaries, molten rock, breaking through to the surface between two plates, hardens along their edges, pushing these plates apart. This process can also cause the movement of all other plates. It is also believed that, in addition to the primary push, the movement of the plates is stimulated by giant heat flows circulating in the mantle (see the article "").
drifting continents
Scientists believe that since the formation of the primary earth's crust, the movement of plates has changed the position, shape and size of the continents and oceans. This process has been called tectonics slabs. Are given various evidence this theory. For example, the outlines of such continents as South America and Africa, look like they once formed a single whole. Undoubted similarities were also found in the structure and age of the rocks that make up the ancient mountain ranges on both continents.
1. According to scientists, the land masses that now form South America and Africa were connected to each other more than 200 million years ago.
2. Apparently, the bottom of the Atlantic Ocean gradually expanded when new rock was formed at the boundaries of the plates.
3. Now South America and Africa are moving away from each other at a rate of about 3.5 cm per year due to plate movement.
Indisputable proof that tectonic plates set in motion was the unprecedented flooding in the history of Pakistan in 2010. More than 1,600 people died, 20 million were injured, and a fifth of the country was under water. On the opposite side of the Indo-Australian Plate, the ocean floor is rising, as evidenced by buoy readings near Australia. The slope of the plate directs water to the east coast of Australia, so in January 2011 Australia experienced a "biblical flood", the flood area exceeded the combined area of France and Germany, the flood is recognized as the most destructive in the history of the country. Near station 55012 is station 55023, which in June 2010 already registered an unprecedented rise of the ocean floor by 400 (!!!) meters. Buoy 55023 first began showing seafloor uplift in April 2010, indicating not only the steady uplift of the eastern edge of the Indo-Australian Plate, but also the flexible parts of that plate that can bend when the plate's position changes. The slabs are heavy and when they topple they can buckle to the point where they become suspended, buckling under the weight of the rock no longer supported by the magma. In essence, a void is created under this part of the slab. Sudden rapid drop in water height June 25, 2010 . actually linked to a 7.1 magnitude quake in the Solomon Islands a day later. This activity, the rise of the plate, has become stronger, and this trend will only increase in the near future. Since the end of 2010, the Sunda Plate has been showing steady subsidence. All the countries that are on the plate - Myanmar, Thailand, Cambodia, Vietnam, Laos, China, Malaysia, the Philippines and Indonesia have experienced record floods this year. The photo shows the coast of cities on the island of Java in Indonesia - Jakarta, Semarang and Surabaya. The photo clearly shows that the ocean swallowed coastline and the coast goes under water.
The Earth Observatory, a division of NASA, admitted that when compared to images from a year ago, Pakistan's elevation above sea level has decreased.
The Indian plate is tilting, and Pakistan has lost several meters of height from this.
To the east of the Indonesian island of Java, in the sea between Java and Bali, a new island grew within a few days. Between eastern Java and Bali, where the Sunda Plate is under pressure as it is pushed down under the Indo-Australian Plate boundary, a new island has appeared. When the platform compresses, compressing, thin spots on it can give rise to deformation, and weak spots on the platform are also found, which can deform in such a way that it has to rise.
Photo of Bali, Indonesia, port on the coast under water. This dive was sudden, within an hour. Similarly, on the northern coast of Java, the Semarang dive.
The sinking of the Sunda Plate has reached the stage where coastal cities such as Jakarta, Manila and Bangkok are in the news due to severe flooding problems. Bangkok, which is set to lose 12 meters of height from the sunda plate sinking, has declared "war" on the rise of water, which they attribute to rainfall from the mountains, but in fact no rainwater not capable drain as the rivers are blocked by backflow from the sea. Local news frankly refers to downgrade, claiming that "sea level rise" is present in the Ayutthaya temple area, which is further inland from Bangkok. And the authorities in Manila, refusing to acknowledge what happened, are telling their rooftop population to just wait it out. Scientists warn of land flooding in Manila and Central Luzon caused by increased flooding. The reason for the flooding of land areas in Greater Manila and nearby provinces may be geological movements associated with processes in the western Markina fault line valley.
In Thailand, more than 800 people have died from the floods and more than 3 million have been affected. The flood is already recognized as the worst in 100 years.
10.08. Residents of the island of Luzon report that they have never seen flooding on this scale, and the rivers in this region still hold water. high level water that for some reason does not go into the ocean.
The reality that the Sunda Plate, which also hosts Vietnam and Cambodia, is sinking, is starting to surface in the press. Press reports from Vietnam repeatedly mention that they are immersed in sea water
"Torrential rains upstream and downstream over the past two days have caused Hue City to sink into seawater." "This year's event is anomalous," said Kirsten Mildren, a spokeswoman for the UN's regional Office for the Coordination of Humanitarian Affairs. "Here you are weeks or months in the water, and it just keeps getting worse."
30.09. In the Mekong River Valley in southern Vietnam and Cambodia, the most powerful ten years of flooding. More than 100 people died as a result.,
bridges and houses of hundreds of thousands of people were destroyed.
The buoy near the Mariana Trench plunged into the water by 15 !!! meters. The Mariana Plate is tilting and moving under the Philippine Plate, and Mariana Trench rolls up. The Marianas will tilt and move closer to the Philippine Islands by 47 miles.
A strip of land 800 m long and 50 m wide appeared in the sea near the Taman Peninsula. Clay layers rose 5 m above sea level.In this area, there is a weak point in the earth's crust and jerks of the plates occur in three directions, the earth has risen from compression.
In the south of Russia in last years seismic activity increased sharply. In the zone special attention Azov and Black Sea. Their coastlines are constantly changing. New islands appear, or, conversely, land areas go under water. Scientists have found that such phenomena are associated with the movement of tectonic plates. Recently, the line of the Azov coast began to change dramatically. Not a single plant, only cracked soil, rocks and sand. More recently, this land was deep under water, but literally overnight, a significant section of the bottom rose five meters up and a peninsula was formed. To understand what force lifted a piece of land weighing hundreds of tons, experts take soil samples every day. After all the measurements, the conclusion is the same - tectonic plates in the area began to actively move.
http://www.vesti.ru/doc.html?id=623831&cid=7
The latest earthquake patterns (monitor http://www.emsc-csem.org/Earthquake/) indicate that the platforms are released, so they move regularly generally- on the example of recent earthquakes at the boundaries of the Antarctic, Philippine and Caribbean plates. As a result, earthquake epicenters are often located on all sides of the platform contour. On the IRIS seismic monitor on November 13, 2011, earthquakes fringing the Antarctic Plate show a clear trend. The Antarctic Plate is moving!
A strong earthquake on November 8, 2011 at the border of the Philippine Plate indicates the movement of this plate. The quake hit exactly on the border of the Philippine Plate, and the next day there was another smaller quake on the opposite side of the plate. This the plate also moves.
The November 12-13, 2011 quakes fringing the Caribbean Plate show that the entire plate is moving under pressure at the junction near Venezuela, the islands of Trinidad and Tobago, being lifted off the Virgin Islands, and being severely crushed where Guatemala meets with Coconut Slab. Caribbean Plate moving, as one whole.
Lithospheric plates have high rigidity and are capable of maintaining their structure and shape unchanged for a long time in the absence of outside influences.
plate movement
Lithospheric plates are in constant motion. This movement, which occurs in the upper layers, is due to the presence of convective currents present in the mantle. Separately taken lithospheric plates approach, diverge and slide relative to each other. When the plates approach each other, compression zones arise and subsequent thrusting (obduction) of one of the plates onto the neighboring one, or subduction (subduction) of adjacent formations. When diverging, tension zones appear with characteristic cracks that appear along the boundaries. When sliding, faults are formed, in the plane of which nearby plates are observed.
Movement Results
In the areas of convergence of huge continental plates, when they collide, mountain ranges arise. In a similar way, at one time the Himalayas mountain system arose, formed on the border of the Indo-Australian and Eurasian plates. The result of the collision of oceanic lithospheric plates with continental formations are island arcs and deep-water depressions.
In the axial zones of the mid-ocean ridges, rifts (from the English. Rift - a fault, a crack, a crevice) of a characteristic structure arise. Similar formations of a linear tectonic structure of the earth's crust, having a length of hundreds and thousands of kilometers, with a width of tens or hundreds of kilometers, arise as a result of horizontal stretching of the earth's crust. Very large rifts are usually called rift systems, belts, or zones.
In view of the fact that each lithospheric plate is a single plate, increased seismic activity and volcanism are observed in its faults. These sources are located within fairly narrow zones, in the plane of which friction and mutual displacements of neighboring plates occur. These zones are called seismic belts. Deep-sea trenches, mid-ocean ridges and reefs are mobile areas of the earth's crust, they are located at the boundaries of individual lithospheric plates. This once again confirms that the course of the process of formation of the earth's crust in these places and is currently continuing quite intensively.
The importance of the theory of lithospheric plates cannot be denied. Since it is she who is able to explain the presence of mountains in some areas of the Earth, in others -. The theory of lithospheric plates makes it possible to explain and foresee the occurrence of catastrophic phenomena that can occur in the region of their boundaries.