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Falling to Earth asteroids

 

Much less powerful than supernova explosions, but much more frequent and intimate events causing catastrophic changes in the planet's surface and the biosphere, taking place in the fall of large meteorites, and cometary nuclei. Found a frequency of a cosmic bombardment. We studied the distribution of ages of large impact craters on the surface of the planet. For this purpose were taken only craters with a diameter more than 10 kilometers, and age was determined by geological methods with an accuracy of ± 20 million years. The number of craters with age from 5 to 250 million years was insignificant - only 13. This information led to the conclusion that the large cosmic bodies falling to Earth is not uniform, but in the form of periodic showers with intervals between them, 28.4 million years.

Able to establish the relationship between cyclic events in the terrestrial biosphere and the epoch of cratering on the planet, which was caused by falling comets and meteorites. For the past 100 million years can clearly be seen synchronicity of these two processes. So, the last peak of extinction and the bombing dated 11 million years BC. Oe. The previous three peaks of mass extinction are located in the following sequence: 38, 65, and 91 million years ago. All of these peaks coincide with the epochs of cratering on the Earth. With high confidence, revealed that the cycle of matches is 27 - 28 million years.

From time to time a swarm of comets, breaks from his "rightful place", which is located in a cloud of Opik - Oort and sent to the sun, meeting "on the road" with the Earth. The Oort Cloud is sending to the sun for about five comets in the year.And in the process of influence "comet showers" in the central region of our planetary system in a relatively short period of time may receive up to 200 comets, and the duration of these "showers" in a 1000 times shorter than the intervals between the showers themselves. There were times when the comet fell to the earth's surface at intervals of about 2000 years. The reasons causing outrage clouds Opik - Oort, could be a massive influence transplutonovogo body, or the motion of the solar system in the plane of the galaxy, a collision with its spiral arms or other areas of high concentration of the substance.

Some idea of the ancient cosmic catastrophes gives a survey of the largest impact craters that have been preserved to this day.

Traces the fall of large meteorites on the Earth's surface are unusual circular geological structures, called "astrobleme" - Star sores. Inside astroblems observed radial deformation of the layers of crushed rocks, minerals, and other unusual signs of a powerful shock blast.Who on earth discovered more than 100 of these ring structures - places the fall of the hypothetical giant meteorites. But it should be noted that the ring structures are very similar to violations of the Earth's surface, emerging after some volcanic eruptions - volcanic calderas.

So the question is whether the geological structure of the ring caused by an impact or volcanic eruption, in each case specifically studied. The origin of some of them remains controversial for many decades. And doubtful largest ring, which were formed hundreds of millions of years ago. Thus, there is an assumption that the Gulf of St. Lawrence in Canada - part of a giant impact crater with a diameter of about 290 km and a depth of about 6 km.

Meteorite craters are divided into two types.

The first type - impact craters of diameter less than 100 m are formed by partial crushing and throwing rocks and having a relatively small due to the fall of meteorites, flying at speeds of up to 2.5 km / s.

The second type - blast craters, resulting in the explosion of a meteorite at the time of the collision with the earth's surface. Large meteorite approaching the earth at a speed of 3-20 km / s, when confronted with it explodes as a result of inhibition of the rocks. The substance of his completely or almost completely vaporized in the explosion. Explosive craters are filled with fractured rock, which are often fused. In some of the largest craters are found peculiar breed, called impakitov. They are almost entirely made up of melted rock, frozen in a glass. In small quantities contained in them, and fragments of unmelted rock.

Rocks subjected to meteorite explosion, broken cone cracks. The crack tip fracture cones indicate the direction from which came the shock wave. Impakity and cones are evidence of the destruction of meteoritic origin of the ancient crater.

Tell you about some of the largest cosmic disasters on our planet, caused by falling asteroids and comets.

The largest of significant impact craters - Popigai basin. It is located in the north of the Siberian platform, in the river basin Khatanga in the valley of its right tributary of the river Popigay. Internal dimensions of the crater is 75 km and the diameter of the outer reaches 100 km. The accident occurred 30 million years ago. Cosmic body at high speed struck the thick sediments of 1200 m and slowed down in the basement rocks of the Siberian platform. According to preliminary estimates, the energy of the explosion reached 10 23 J, ie, a

1000 times greater than with the strongest volcanic explosion. On the conditions that existed at the epicenter of the explosion can be judged by what is found in the crater of the catastrophe caused by minerals.

These minerals are able to obtain an artificial way for shock pressures of a million a bar and a temperature of about 1000 ° C. The ejected during the explosion large blocks of crystalline basement rocks platforms scattered over a distance of 40 km from the edge of the crater. Space explosion caused the melting of the rocks, resulting in lava rich in silica (65%), sharply distinct in composition from the underlying basaltic eruption of the Siberian platform.

The second largest impact crater located near the city of Gorky. With the help of geological mapping and drilling has been found Puchezh-Katun basin about 100 km in diameter, probably caused by a meteorite.

Diameter of about 50 km Kars has a crater on the Pai-Khoi Ridge. He filled the rock fragments in the explosion, the melted and partially frozen in a glassy mass.

In 1920, the famous Finnish scientist, geologist, Eskola explored the northern part of Lake Ladoga. He drew attention to the unusual lava near the lake Yanisyarvi that the composition very similar to impakity bomb craters. Yanisyarvi Lake, located 95 km from the town of Sortavala, has a size of 14x26 km and is probably an ancient meteorite crater. In favor of this show and two rocky islets in the center of the lava lake.

In Ukraine, found Boltyshsky crater (diameter about 25 km), resulting from a meteorite impact 100 million years ago. The oldest meteorite crater (diameter 20 km) in our country is in Karelia, age more than 1 billion years.

In the Vinnitsa region., Near the village of Ilintsi recently discovered impact crater with a diameter of 4 km. It was formed about 100 million years ago. Craters of diameter 3 - 5 km were found east of the city of Vinnitsa and south-east of Gdov.

In the region of Kaluga buried explosive crater with age 250 million years. The diameter of its reaches 15 km.

Abroad, a well-studied large crater Reese, within which lies the town of Nordlingen (Germany). The crater was formed as a result of impact and explosion of a giant meteorite some 15 million years ago. The resulting depression reaches 20 km in diameter. Seismic surveys carried out in the basin have shown that a 35-meter layer of lake sediments is hidden inside an underground basin. Its depth is not less than 700 meters and a diameter of about 10 km. The crater is filled with fragmented, sintered and partially molten rock. Loosened rock, filling the crater causes a decrease in the gravity field over the surrounding countryside. This decrease corresponds to the mass deficit in the crater of 30 - 60 billion tons Consequently, at the time of the explosion was thrown up to 20 km 3 of rock.

In France Rosheshuar crater (diameter about 15 km) formed 150-170 million years ago.

By "young" craters - up to age 15 million years - are Bosumtvi in Ghana (West Africa), which is a lake (diameter of 9.8 km, depth 350 m), and Chubb Ungava Peninsula in Canada (diameter 3.4 km, depth 390 m). Roter Kamm meteorite crater, discovered in 1965 in South-West Africa, 95 km from the mouth of the Orange River, up to 30 meters of the crater bottom is filled up, therefore, the total depth is even greater. Kaltsevogo transverse dimensions of the shaft, stacked debris gneiss, about 2.4 km above the surrounding terrain height of 90 m crater of Locarno in India is the diameter of 1.8 km and a depth of 120 m 

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Автор: admin от 05.03.2012





  

 

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