What are they for? modern methods studying the Earth?
Answers:
Research methods in geography today remain the same as before. However, this does not mean that they do not undergo changes. Appear latest methods geographical research, allowing to significantly expand the capabilities of humanity and the boundaries of the unknown. But before considering these innovations, it is necessary to understand the usual classification. Methods of geographical research are various ways obtaining information within the science of geography. They are divided into several groups. So, the cartographic method is the use of maps as the main source of information. They can give an idea not only of the relative position of objects, but also of their sizes, the extent of distribution of various phenomena, and a lot of other useful information. The statistical method says that it is impossible to consider and study peoples, countries, natural objects without the use of statistical data. That is, it is very important to know what the depth, height, reserves are natural resources of a particular territory, its area, the population of a particular country, its demographic indicators, as well as production indicators. The historical method implies that our world has developed and everything on the planet has its own rich history. Thus, in order to study modern geography, it is necessary to have knowledge about the history of the development of the Earth itself and the humanity living on it. The methods of geographical research are continued by the economic-mathematical method. This is nothing more than numbers: calculations of mortality, fertility, population density, resource provision. The comparative geographical method helps to more fully evaluate and describe the differences and similarities geographical objects. After all, everything in this world is subject to comparison: smaller or larger, slower or faster, lower or higher, and so on. This method makes it possible to classify geographical objects and predict their changes. Methods of geographical research cannot be imagined without observations. They can be continuous or periodic, areal and route, remote or stationary, however, they all provide the most important data on the development of geographical objects and the changes that they undergo. It is impossible to study geography while sitting at a table in an office or at school desk in the classroom, you need to learn to extract useful information from what you can see with your own eyes. One of important methods Geography research has been and remains a method of geographic zoning. This is the identification of economic and natural (physical-geographical) regions. The method of geographic modeling is no less important. We all know from our school days the most striking example of a geographical model - the globe. But modeling can be machine, mathematical and graphical. Geographic forecast is the ability to predict the consequences that may arise as a result of human development. This method allows us to reduce the negative impact of human activities on environment, avoid undesirable phenomena, rationally use all kinds of resources, and so on. Modern methods of geographical research have revealed to the world GIS - geographic information systems, that is, a complex of digital maps linked to them software and statistics, which give people the opportunity to work with maps directly on the computer. And thanks to the Internet, satellite positioning systems appeared, popularly known as GPS. They consist of ground-based tracking equipment, navigation satellites and various devices that receive information and determine coordinates. All these methods are interconnected. For example, it is impossible to study any country completely if you exclude at least one of these methods. There are many examples, knowing the methods you can compose them yourself...
When all the continents were discovered and mapped geographic Maps, the study of the Earth continued. New expeditions went to the Earth's poles, to the bottom of the deepest ocean trench and to the highest peak.
Polar exploration
Reaching the North and South Poles has been the life goal of many explorers. The American tried to conquer the North Pole three times and reached it in 1909.
Having learned about the success of R. Peary, the Norwegian Roald Amundsen decided to conquer the South Pole. In 1911, having reached the Antarctic coast on the ship Fram, he and four comrades set off on a sleigh pulled by dogs. Brave travelers reached the South Pole, raising the Norwegian flag over it.
Beginning in 1959, permanent scientific stations began to be located in Antarctica. They belong different countries, therefore called the continent of the world. Research on Antarctica is very important because it has a significant impact on the climate of even parts of the Earth distant from it. Arctic research continues. Countries whose territories are washed by the Arctic Ocean especially actively participate in them. The advantage in research belongs to Russia. It has been outfitting polar expeditions to the Arctic for almost a century. Very large studies were carried out in 2007 on the ship Akademik Fedorov with the support of the nuclear icebreaker Rossiya. Scientists have studied sea currents, ice thickness, ocean depth. The Mir deep-sea submersibles were lowered to the bottom of the ocean near the North Pole.
Ocean Exploration
As a result of special expeditions to the ocean floor in the 20th century, huge mountain ranges, many underwater volcanoes, and deep depressions were discovered. There were much more volcanoes in the oceans than on land. In 1960, researchers Jacques Piccard and Don Walsh in a special apparatus - a bathyscaphe - sank to the bottom of the world's deepest Mariana Trench, to a depth of 11,022 meters. It turned out that there is life at the bottom of even the deepest depressions. French oceanographer Jacques Cousteau invented scuba gear, with which you can swim freely underwater.
Other studies
In 1953, New Zealander Edmund Hillary and Nepalese representative Norgay Tensing for the first time conquered the highest point on Earth - Mount Chomolungma. Having risen to the top, they hoisted the flags of their countries and the UN flag on it, dedicating their victory to all the people of the Earth.
The most important achievement in Earth exploration in the 20th century was the study upper layers atmosphere. Since the second half of the 20th century spaceships with astronauts on board participated in studying the Earth from space. Since then, new space research methods have appeared in geography, with the help of which scientists obtain information about our planet today.
Earth exploration has not yet been completed. The source of the Amazon River has not yet been precisely established; many plants and animals common in the forests along the banks of this river remain unexplored. Scientists penetrated the earth’s surface only to a depth of 12 kilometers, drilling an ultra-deep well. Research continues on the ice of Antarctica and the depths of the World Ocean.
Gravimetry is a branch of science about measuring quantities characterizing the Earth’s gravitational field and using them to determine the shape of the Earth and study its general internal structure, its geological structure upper parts, solving some navigation problems, etc.
In gravimetry, the Earth's gravitational field is usually set by the field of gravity (or the acceleration of gravity, which is numerically equal to it), which is the result of two main forces: the force of attraction (gravity) of the Earth and the centrifugal force caused by its daily rotation. Centrifugal force directed from the axis of rotation reduces the force of gravity, and to the greatest extent at the equator. The decrease in gravity from the poles to the equator is also due to the compression of the Earth.
The force of gravity, that is, the force acting on a unit mass in the vicinity of the Earth (or another planet) consists of the forces of gravity and the forces of inertia (centrifugal force):
where G - Gravitational constant, mu - unit mass, dm - mass element, R - radius vectors of the measurement point, r - radius vector of the mass element, w - angular velocity rotation of the Earth; the integral is taken over all masses.
The gravity potential, accordingly, is determined by the relation:
where is the latitude of the measurement point.
Gravimetry includes the theory of leveling heights, processing of astronomical and geodetic networks in connection with variations in the Earth's gravitational field.
The unit of measurement in gravimetry is Gal (1 cm/s2), named after the Italian scientist Galileo Galilei.
Determinations of gravity are made by the relative method, by measuring with the help of gravimeters and pendulum instruments the difference in gravity at the studied and reference points. The network of reference gravimetric points throughout the Earth is ultimately connected with a point in Potsdam (Germany), where at the beginning of the 20th century the absolute value of the acceleration of gravity was determined by revolving pendulums (981,274 mgl; see Gal). Absolute determinations of gravity involve significant difficulties, and their accuracy is lower than relative measurements. New absolute measurements, produced at more than 10 points on Earth, show that the given value of the acceleration of gravity in Potsdam is apparently exceeded by 13-14 mgl. After completion of this work, a transition to a new gravimetric system will be carried out. However, in many gravimetry problems this error is not significant, because To solve them, it is not the absolute values themselves that are used, but their differences. The absolute value of gravity is determined most accurately from experiments with free fall tel in vacuum chamber. Relative determinations of gravity are made by pendulum instruments with an accuracy of several hundredths of a mg. Gravimeters provide slightly greater measurement accuracy than pendulum instruments, are portable and easy to use. There is special gravimetric equipment for measuring gravity from moving objects (underwater and surface ships, aircraft). The instruments continuously record changes in the acceleration of gravity along the path of a ship or aircraft. Such measurements are associated with the difficulty of excluding from the instrument readings the influence of disturbing accelerations and tilts of the instrument base caused by pitching. There are special gravimeters for measurements at the bottom of shallow pools and in boreholes. The second derivatives of the gravitational potential are measured using gravitational variometers.
The main range of gravimetry problems is solved by studying the stationary spatial gravitational field. To study the elastic properties of the Earth, continuous recording of variations in gravity over time is carried out. Due to the fact that the Earth is heterogeneous in density and has irregular shape, its external gravitational field is characterized by a complex structure. To solve various problems, it is convenient to consider the gravitational field as consisting of two parts: the main one - called normal, which changes with latitude according to a simple law, and the anomalous one - small in magnitude, but complex in distribution, caused by inhomogeneities in the density of rocks in the upper layers of the Earth. The normal gravitational field corresponds to some idealized model of the Earth that is simple in shape and internal structure (an ellipsoid or a spheroid close to it). The difference between the observed gravity and the normal one, calculated using one or another formula for the distribution of normal gravity and given appropriate corrections to the accepted level of heights, is called the gravity anomaly. If such a reduction takes into account only the normal vertical gravity gradient of 3086 etvos (i.e., assuming that there is no mass between the observation point and the reduction level), then the anomalies obtained in this way are called free-air anomalies. Anomalies calculated in this way are most often used in studying the figure of the Earth. If the reduction also takes into account the attraction of a layer of mass considered homogeneous between the levels of observation and reduction, then anomalies called Bouguer anomalies are obtained. They reflect heterogeneities in the density of the upper parts of the Earth and are used in solving geological exploration problems. Gravimetry also considers isostatic anomalies, which specifically take into account the influence of masses between the earth's surface and the surface level at a depth at which overlying masses exert the same pressure. In addition to these anomalies, a number of others are calculated (Preya, modified Bouguer, etc.). Based on gravimetric measurements, gravimetric maps with isolines of gravity anomalies are constructed. Anomalies of the second derivatives of the gravity potential are determined similarly as the difference between the observed value (previously corrected for the terrain) and normal value. Such anomalies are mainly used for mineral exploration.
In problems involving the use of gravimetric measurements to study the figure of the Earth, a search is usually carried out for the ellipsoid that best represents geometric shape and the external gravitational field of the Earth.
When studying the internal structure of our planet, visual observations of natural and artificial rock outcrops, drilling wells and seismic exploration are most often carried out.
Rock outcrop is the outcropping of rocks onto the earth's surface in ravines, river valleys, quarries, mine workings, and on mountain slopes. The rocks in the outcrop are usually hidden by a thin layer of talus, so the first step is to clear it of excess material. When studying an outcrop, attention is paid to what rocks it is composed of, what the composition and thickness of these rocks are, and the order of their occurrence (Fig. 2). The exposure is carefully described, sketched or photographed. Samples are taken from each layer for further study in the laboratory. Laboratory analysis of samples is necessary in order to determine the chemical composition of rocks, their origin and age.
Drilling wells allows you to penetrate deeper into the Earth. During drilling, rock samples - cores - are extracted. And then, based on studying the core, the composition, structure, and occurrence of rocks are determined and a drawing of the drilled strata is constructed - a geological section of the area. Comparison of many sections makes it possible to establish how the rocks are deposited and to draw up a geological map of the territory.
When studying the internal structure of the Earth, deep and ultra-deep wells are especially important. The deepest well is located on the Kola Peninsula, where the drill reached a mark of more than 12 km.
Figure 2. Outcrop diagram of horizontal rocks cut by a volcanic vein.
The disadvantage of outcrop observations and drilling operations is that they only allow us to study a thin film of the earth's surface. Thus, the depth of even the Kola superdeep well is less than 0.25% of the radius of the Earth.
The seismic method makes it possible to “penetrate” to great depths.
This method is based on the idea that seismic waves (from the Greek seismos - wave, vibration) propagate at different speeds in media of different densities: the denser the medium, the greater the speed. At the boundary of two media, some of the waves are reflected and, like circles on water goes back, and the other one spreads further.
By artificially exciting waves on the Earth's surface through explosions, seismologists record the time it takes for the reflected waves to return. For these purposes, a recorder device is used - a seismograph.
There are two types of seismic waves - longitudinal and transverse. Longitudinal ones propagate in all media - solid, liquid and gaseous, and transverse ones - only in solid media.
Knowing at what speed waves propagate in sands, clays, granites, basalts and other rocks, by the time they travel “there and back”, you can determine the depth of rocks that differ in density.
Conclusion
The development of ideas about the Earth was facilitated by the great geographical discoveries. If astronomical knowledge provided information about the shape and size of the Earth, then great geographical discoveries made it possible to verify this information, so to speak, by touch.
The accumulation of astronomical, geographical and geological knowledge determined the further development of ideas about the internal structure of the Earth. Mystical views have become incompatible with scientific data. Ideas about channels and voids inside the Earth, which determine its structure, faded into the background: in addition to them, the idea of the existence of a central fire inside the Earth appeared. On the question of the reasons for changes in the Earth's topography, the struggle between fire and water continued - the struggle between supporters of the leading role of each of these factors.
At the beginning of the 18th century, ideas about a solid core (passive central fire) appeared. Many believed that the Earth was formed from a fiery melt and then cooled from the surface to the center. The mistake of many authors was that they, being limited by national frameworks and concepts obtained within one country, explained the structure of the entire globe based on the structure of the mountains in their homeland. Along with ideas about the solid interior of the Earth, in the second half of the 18th century. There were also ideas that at great depths inside the Earth there is fiery liquid matter, which, unlike the passive central fire of previous researchers, actively affects the surface of the Earth.
During the 19th century. The dominant idea in ideas about the internal structure of the Earth was the idea that the entire globe is filled with a raging sea of fire, which is covered only by a thin crust. The entire 19th century Therefore, I singled it out in a special period, despite the presence of other views on the structure of the Earth. As I saw, the development of ideas about the internal structure of the Earth began from the middle of the 17th century. thus: the idea of a passive central fire (until the middle of the 18th century) and the idea of the development of the Earth as a planet and the active influence of its interior on the surface of the Earth (second half of the 18th century). These two directions seemed to merge together at the beginning of the 19th century, when ideas about the fiery-liquid interior of the Earth, covered by a thin earth’s crust, and the active influence of this melt on the earth’s crust, became dominant. At the same time, at the beginning of the 19th century, despite the dominance of the idea of the fiery state of the Earth's interior, in such a question as the causes of earthquakes, there was still a hypothesis from an earlier period about channels and voids inside the Earth and about the action of compressed vapors and gases causing earthquakes. Only from the beginning of the 19th century. in accordance with general ideas, the cause of earthquakes began to be considered the uplifting effect of the fiery melt. Along with this, in the 19th century. There were also fully formed ideas about the solid and even iron core of the Earth.
A detailed analysis of seismometry data and all the achievements of seismology was made in the first quarter of the 20th century. There were many different statements about the internal structure of the Earth in the first half of the 20th century. by petrographers. Concepts about the plastic or liquid subcrustal layer in the first decades of the 20th century. formed the basis for many versions of the hypothesis of horizontal movement of continents. Considering the advances in science and technology in the field of astronautics, deep-sea drilling, and experiments at high temperatures and pressures, one can hope that the main provisions of the hypothesis can be tested in the near future.
The modern period is characterized by the development of methods for studying the internal structure of the Earth.
In the XVIII and 19th centuries Astronomers used a precise method of triangulation to measure the Earth.
In this case, the direct measurement of large lengths on Earth is replaced by the determination of angles in a system of triangles divided on the convex earth's surface. A comparison of such measured arcs, drawn both along the meridians and in longitude, through various continents, made it possible to get an idea of the shape and actual dimensions of the Earth's solid shell.
The earth turned out to be different from the ball; only in the roughest approximation can it be taken for a sphere with a radius of 6371 km. In fact, it is flattened at the poles in accordance with the laws of rotation of bodies and Newton's theory of gravity. The polar radius is almost 21 km shorter than the equatorial radius. Therefore, to a second approximation, the Earth can be considered a slightly flattened sphere, the so-called spheroid, or ellipsoid of revolution. The elements of this ellipsoid serve as the basis for constructing accurate maps of the earth's surface.
We will present data on the ellipsoid that were established in 1940 by Soviet scientists: the equatorial radius is 6378 km, the polar radius is 6356.9 km. Therefore, the length of the Earth's meridian, i.e., the circle passing through the poles, is 40,010 km, and the area of the entire surface is 510 million km 2. Of this, land accounts for only 29%; the rest, that is, almost three-quarters of the entire surface, constitutes a gigantic area of oceans and seas.
However, the actual shape of the Earth is also different from an ellipsoid; The continents protrude somewhat above the surface of the oceans, and there is much more land in the Northern Hemisphere of the Earth than in the Southern. Finding out the exact figure of the Earth is of great interest. Therefore, scientists continue precise measurements using geodesy methods, determining the sides and angles of triangles and constructing geodetic signs, which are located at the vertices of these triangles. The force of gravity is measured at all accessible points on the Earth, for which extremely accurate gravimeters have recently been used. The data obtained make it possible not only to judge the heterogeneities in the earth's crust and mineral deposits, but also to study the shape of the Earth.
The mass of the Earth (the amount of its substance) is 6000 billion billion tons. Dividing the mass by the volume, we get the average density of the earth's substance, which turns out to be 5.5 times greater than water. And since average density at the surface is only 2.6 relative to water, the substance internal regions The earth must be very compacted and match the density of iron or steel.
Recently, to study the size and shape of the Earth, they began to use artificial satellites. Based on the laws of celestial mechanics, astronomers are able to determine the exact orbits of satellites and, through continuous observations, monitor all changes in their movement. Therefore, you can always know where, when and at what altitude the satellite flies. Accurate measurements of the satellite's position in the sky, made from several points on the Earth, make it possible to judge the positions of the observers themselves, i.e., they allow one to check geodetic data on the earth's surface. The results are in some cases more accurate than with geodetic determinations.
The method of observing satellites is especially important when clarifying the question: do the continents shift relative to each other? Is it true that the American continent moved away from the western borders of Europe and Africa in times long past, as some scientists suggest? Indeed, the line east coast America fits well western shores Europe and Africa. To clarify this issue you need a large number of accurate observations. Some time will pass, and scientists will be able to answer the question about the movement of continents.
Rockets and satellites are also increasingly used for direct observation of the Earth from great heights, from interplanetary space. All. We saw wonderful color photographs of the earth's surface taken by G. S. Titov from the Vostok-2 satellite. There is already a permanent meteorological service from satellites equipped with television installations. Using the images on the screens of earthly televisions, you can monitor the weather conditions in different regions of the Earth and study the movement of cyclones.
Instruments carried on satellites record the state of the magnetic field around the Earth, the number and characteristics of cosmic particles, meteor particles, ultraviolet and x-ray radiation, and much more. The use of satellites made it possible in 1958-1959. discover the existence of the Earth's corona - two or even three belts of high-energy particles - fast protons and electrons held by the earth's magnetic field. These radiation belts apparently play a very important role in various atmospheric phenomena and in life on Earth.