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Geological time (by Anna Trotsko)
Geological time - the time during which the development of the Earth. The development of our planet is associated with such major events as the formation of the earth's crust and development of living organisms.

Historical studies of geological process
Getton described the third type of rocks, which include basalt and granite. This type is called igneous. Getton understand that sedimentary, metamorphic and igneous rocks, until then hidden in the depths of the Earth, often rise to the surface, forming mountains and new areas of land to, in turn, will also at a certain time be destroyed. Getton realized that the study of the processes taking place slowly, but because the history of the Earth must be very long. And although to determine her age, he could not, Getton concluded that "no indication of the beginning nor the Earth, nor on the end of it we have." After gathering all the information, Smith in 1815 he published a geological map of England and Wales. The map reflects where outcrop rocks, and also gave an idea about their relative age, from the early to the lateAfter collecting all this information, Smith in 1815 published a geological map of England and Wales. Map reflects where outcrop of rock layers and give an idea of ​​their relative age - from the early to late.
 * The father of modern Geology, most geologists believed James Gattone (1726-1797), a Scottish physician and scientist, author of "The Theory of the Earth", created in 1785 based on research and observations of natural processes.He was one of the first to realize that the surface of the earth changes all the time. Under the influence of the weather phenomena, for example, frost - rock is being eroded and the rivers carry the debris into lakes and seas where such accumulated layers of sediments like sand and silt, formation of new rocks - sedimentary.
 * An important contribution to the understanding of geologic time, made by another Briton William Smith (1769-1839). He worked on the construction of canals which in the early era of the industrial revolution in England transported goods. While the workers were digging trenches, Smith collected the fossils which were found in underground layers.Smith concluded that the rocks, which are found in various places and contain the same fossils - the same age. Smith came to the conclusion that the rocks that are found in different places contain the same fossils, same age.

The creation of a geological timeline of the Earth
The scale of the relative age of rocks geologists created on the basis of the law of the layers, whereby in undisturbed sedimentary rocks, younger layers are always placed over older. Over time, geologists have understood the sequence, which occurred the formation of the layered rocks on the planet. This allowed us to construct a timeline of Earth's history. Just as it's easier to study history, breaking it down into periods existence of different civilizations and geologists have divided earth's history into segments, each of which had its own name and distinctive features.

The structure of the geological scale of the Earth
Using a large number of different fossils in phanerozoic rocks the time of their appearance are divided into three age - Paleozoic (lit. "ancient life"), Mesozoic ("middle life") and Cenozoic ("new life"). Each era is divided into periods. Stratigraphic scale gave an idea of the relative age of rocks and found the names of eras and periods, but how long was each of these intervals, geologists did not know.
 * The first period of the Paleozoic era - Cambrian. Modern geologists, as a rule, includes all rocks formed before the Cambrian period, Precambrian. The Cambrian was named in honor of Cambria (the Latin name of Wales), and Perm - Russian city of Perm.
 * The Ordovician and Silurian periods owe their names to the ancient tribes that inhabited Britain. Carboniferous and creed of any periods named for the rocks associated with them. In addition, the American geologists divide the Carboniferous period into two: mscsi (lower Carboniferous) and Pennsylvanian (upper Carboniferous) periods.
 * The Cenozoic era is divided into two periods: Tertiary and Quaternary. Rocks that were formed in the Tertiary and Quaternary periods, contain so much organic remains that these segments were also divided into smaller ones, called ages, and those in turn - for several centuries.

The determination of the age of the Earth
One of them relied on the speed of rotation of the Earth and the amount of heat radiated by the Sun. The other was based on the hypothesis that first the Earth was a glowing ball, so I had to count how long she had to cool to current temperature. According to the calculations it appeared that the Ground is not more than 100 million years. But they were far from the truth. Radioisotope dating has enabled geologists to establish the absolute age of rocks, the beginning and duration of eras, periods and epochs. And yet, from time to time, when find and date new samples of radioactive rocks, the casualty figures have to be revised. Radiometric methods have also shown that the age of the Earth measured not even in millions and billions of years.
 * Serious attempts to determine the age of rocks was done in the late 19th century. Charles Lyell (1797-1875), an eminent geologist and friend of Charles Darwin, came from the fact at what stage of evolution were fossils. So, he estimated that the interval between the beginning of the Cambrian period, when they first started showing up in large numbers, and our time was about 240 million years. But his calculations were imprecise and value is not represented.
 * Outstanding British physicist Kelvin (1824-1907) tried to determine the age of the Earth in several ways.
 * The fallacy of the calculations of the Kelvin were able to prove after the discovery in 1896 of radioactivity. Radioactive substances found in certain rocks emit particles of high energy and hard rays and as a consequence break up at a constant speed. For example, the final product of the radioactive decay of uranium is lead, so the age of the sample of uranium can be set, defining the amount of lead contained therein.

Literature
The tree of knowledge, Marshall Cavendish Collections, V. 51-54.