Forces of the Earth. Gravitational force of the Earth

Every change always requires some effort. Any change will not happen without any influence. And an obvious example is our planet, which was formed under the influence of various factors for billions of years. It is also important that the constant processes of changing the Earth are the result not only of external forces, but also internal ones, those that are hidden deep in the depths of the geosphere.

And if in two or three decades the face of our planet can easily change beyond recognition, then obviously it will not be superfluous to understand those processes whose influence led to this.

Changes from within

Elevations and depressions, irregularities and roughness, as well as many other features of land relief - all this is constantly updated, collapsing and formed by powerful internal forces. Most often, their manifestation remains outside our field of vision. However, even right at this moment, the Earth is smoothly subjected to certain changes, which in the long term will become much more significant.

Ever since the time of the ancient Romans and Greeks, uplifts and subsidence of various parts of the lithosphere have been noticed, causing all changes in the outlines of the seas, land and oceans. Many years of scientific research using various technologies and instruments fully confirm this.

Growth of mountain massifs

The slow movement of individual sections of the earth's crust gradually leads to their overlapping. Faced in a horizontal movement, their thicknesses bend, crumple and transform into folds of different scales and steepness. In total, science distinguishes two types of mountain-forming movements (orogenesis):

• Bending of the seams - forms both convex folds (mountain ranges), and concave (cavities in mountain massifs). This is what caused the name of the folded mountains, which gradually break down over time, leaving only the base. On it the plains are formed.
• Rupture of strata - strata of rocks can not only crumple into folds, but also be exposed to faults. In this way, folded-block (or simply blocky) mountains are formed: skids, grabens, horsts and their other components arise with vertical displacement (upward / downward lifting) of parts of the earth's crust relative to each other.

But the inner strength of the Earth is capable not only of crushing the plains into the mountains and destroying the former outlines of the highlands. Movements of lithospheric plates also generate earthquakes and volcanic eruptions, which are often accompanied by monstrous devastation and human deaths.

Breath from under the earth

It's hard to even imagine that the familiar concept of "volcano" in ancient times had a much more menacing tone. At first, the true reason for this phenomenon was customarily attributed to the disgrace of the gods. Streams of magma erupted from the bowels were regarded as a severe punishment from above for mortal mortalities. Catastrophic losses due to volcanic eruptions have been known since the dawn of our era. Thus, for example, the majestic Roman city of Pompeii was wiped from the face of the planet Earth. The power of the planet at that time was manifested by the crushing power of the now widely known Vesuvius volcano. By the way, the authorship of this term is historically fixed for the ancient Romans. So they called their god of fire.

For a modern man, a volcano is a cone-shaped elevation above cracks in the cortex. Through them on the surface of the earth, the sea or ocean floor, magma erupts along with the gases and debris of rocks. In the center of this formation there is a crater (in translation from the Greek - "cup"), through which the ejection occurs. When solidified, magma turns into lava and forms the outlines of the volcano itself. However, even on the slopes of this cone, cracks often appear, forming parasitic craters.

Quite often, eruptions are accompanied by earthquakes. But the greatest danger for all living things is emissions from the bowels of the Earth. The release of gases from magma occurs very quickly, so powerful explosions are subsequently a common occurrence.

According to the type of action, volcanoes are divided into several types:

• Those in operation are those whose last eruption is documented. The most famous among them are: Vesuvius (Italy), Popocatepetl (Mexico), Etna (Spain).
• Potentially acting - erupt very rarely (every few thousand years).
• Extinct - such a status have volcanoes, the latest eruptions of which documentary evidence is not preserved.

The influence of earthquakes

Shifts of rocks often provoke rapid and severe fluctuations in the earth's crust. Most often this occurs in the high mountains region - these areas are still continuously being formed.

The place of origin of the shifts in the depths of the earth's crust is called the hypocentre (focus). From it are propagated waves, which create oscillations. The point on the surface of the earth, directly below which the focus is the epicenter. In this place the strongest tremors are observed. As they continue to move away from this point, they gradually fade.

The science of seismology, which studies the phenomenon of earthquakes, identifies three main types of earthquakes:

1. Tectonic - the main mountain-forming factor. Occurs as a result of collisions of oceanic and continental platforms.
2. Volcanic - arise as a result of flows of red-hot lava and gases from under the earth's interior. Usually they are rather weak, although they can last several weeks. Most often are harbingers of volcanic eruptions, which is fraught with far more serious consequences.
3. The landslide - arise as a result of the collapse of the upper layers of the earth, covering the emptiness.

The strength of earthquakes is determined by a ten-point Richter scale with the help of seismological instruments. And the larger the amplitude of the wave that appears on the earth's surface, the more noticeable will be the damage. The weakest earthquakes, measured in 1-4 points, can be ignored. They are registered only by special sensitive seismological instruments. For people, they manifest themselves maximum in the form of shaking glasses or slightly moving objects. Most of them are completely invisible to the eye.

In turn, fluctuations of 5-7 points may well lead to various damage, albeit minor. Stronger earthquakes already pose a serious threat, leaving behind destroyed buildings, almost completely destroyed infrastructure and human losses.

Every year, seismologists register about 500 thousand oscillations of the earth's crust. Fortunately, only a fifth of this number is really felt by people and only 1,000 of them cause real damage.

More details about what affects our common home from outside

Continuously changing the relief of the planet, the internal strength of the Earth does not remain the only formative element. A number of external factors also directly participate in this process.

By destroying numerous irregularities and filling underground depressions, they bring a tangible contribution to the process of continuous change of the Earth's surface. It is worth noting that in addition to the flowing waters, devastating winds and the action of gravity, we directly influence our own planet.

Modified by the wind

The destruction and transformation of rocks mainly occurs under the influence of weathering. It does not create new relief forms, but destroys hard materials to a loose state.

In open spaces where there are no forests and other obstacles, sandy and clay particles can move by considerable distance with winds. Subsequently, their clusters form aeolian relief forms (the term is derived from the name of the ancient Greek god Eol - lord of the winds).

An example is the sandy hills. Barkhans in deserts are created only when exposed to wind. In some cases, their height reaches hundreds of meters.

Sedimentary mountain sediments consisting of dust particles can accumulate in the same way. They have a grayish-yellow color and are called loess.

It should be remembered that, moving with great speed, different particles not only just accumulate in new formations, but also gradually destroy the relief encountered on their way.

Weathering of rocks can be of four types:

1. Chemical - is the chemical reactions between minerals and the external environment (water, oxygen, carbon dioxide). As a result, rocks are destroyed, their chemical component suffers changes with the further formation of new minerals and compounds.
2. Physical - causes mechanical decay of rocks under the influence of a number of factors. First of all, physical weathering occurs with a significant temperature fluctuation during the day. Winds, along with earthquakes, volcanic eruptions and mudflows, likewise are factors of physical weathering.
3. Biological - is carried out with the participation of living organisms, the activity of which leads to the creation of a qualitatively new formation - soil. The influence of animals and plants is manifested in mechanical processes: the crushing of rocks by roots and hoofs, burrowing burrows, etc. Particularly large-scale role in biological weathering belongs to microorganisms.
4. Radiation, or solar weathering. A characteristic example of the destruction of rocks with a similar effect is the lunar regolith. Along with this, radiation weathering also affects the previously listed three types.

All these types of weathering are often manifested in combination, combining in various variations. However, different climatic conditions also affect one's predominance. For example, in places with a dry climate and in high-altitude areas, there is often physical weathering. And for areas with a cold climate, where temperatures often fluctuate to 0 degrees Celsius, not only weathering by frost, but also organic, combined with chemical, is characteristic.

Gravitational impact

No list of external forces of our planet will not be complete, if we do not mention the fundamental interaction of all material bodies - this is the gravitational force of the Earth.

Destroyed by numerous natural and artificial factors, rocks are always prone to moving from lower parts of the soil to lower ones. This is how the landslides, screes, are born, and they land with landslides. The gravitational force of the Earth at first glance may seem something invisible against the background of powerful and dangerous manifestations of other external factors. However, all their impact on the relief of our planet would simply be leveled without universal gravitation.

Let's take a closer look at the impact of gravity. In the conditions of our planet, the weight of any material body is equal to the force of gravity of the Earth. In classical mechanics this interaction describes the Newtonian law of universal gravitation known from the school bench. According to him, F gravity is equal to the product of m by g, where m is the mass of the object, and g is the free fall acceleration (always equal to 10). In this case, the gravity of the Earth's surface affects all the bodies located both directly on it and near it. In the case when the body is affected exclusively by gravitational attraction (and all other forces are mutually balanced), it undergoes a free fall. But for all its ideality, such conditions, where the forces acting on the body at the surface of the Earth, in fact, are leveled, are characteristic of a vacuum. In everyday reality, you have to deal with a completely different situation. For example, the amount of air resistance affects the incident object in the air. And though still the force of gravity of the Earth will be much stronger, this flight will no longer be truly free by definition.

It is interesting that the impact of attraction exists not only in the conditions of our planet, but also at the level of our solar system as a whole. For example, what attracts the moon more? Earth or Sun? Without a degree in astronomy, many will probably be surprised by the answer.

Because the gravitational force of the satellite by the Earth is less than 2.5 times the solar one! It will be reasonable to think about how the heavenly body does not tear the Moon from our planet with such strong influence? In this respect, the magnitude, which is equal to the gravitational force of the Earth relative to the satellite, is much inferior to that of the sun. Fortunately, science is able to answer this question.

Theoretical cosmonautics uses several concepts for such cases:

• The sphere of action of the body M1 is the surrounding space around the object M1, within which the object m moves;
• The body m is an object freely moving in the sphere of action of the object M1;
• The body of M2 is an object that exerts a disturbing effect on this motion.

It would seem - the decisive must be gravitational force. Earth attracts the moon much weaker than the Sun, but there is another aspect that has the final effect.

The whole point is that M2 tends to break the gravitational connection between the objects m and M1 by giving them different accelerations. The value of this parameter directly depends on the distance of objects to M2. However, the difference between the accelerations sent by the body M2 to m and M1 will be less than the acceleration difference m and M1 directly in the gravitational field of the latter. This nuance is the reason why M2 is not able to tear m from M1.

Let's imagine a similar situation with the Earth (M1), the Sun (M2) and the Moon (m). The difference of those accelerations created by the Sun in relation to the Moon and the Earth is 90 times less than the average acceleration that characterizes the Moon in relation to the Earth's sphere of action (its diameter is 1 million km, the distance between the Moon and Earth is 0.38 million Kilometers). The decisive role is played not by the force with which the Earth attracts the Moon, but by the large difference in the acceleration between them. Thanks to this, the Sun is able only to deform the Moon's orbit, but not to tear it away from our planet.

Let's go even further: the impact of gravity is to a different degree characteristic of other objects of our solar system. What exactly does it influence, given that gravity on Earth is significantly different from that of other planets?

This will affect not only the movement of rocks and the formation of new forms of relief, but also their weight. Be sure to note that this parameter is determined by the magnitude of the attractive force. It is directly proportional to the mass of the planet in question and inversely proportional to the square of its radius.

If our Earth were flattened at the poles and stretched out in the Equator, the weight of any body on the entire surface of the planet would be the same. But we do not live on an ideal ball, and the equatorial radius is longer than the polar radius by about 21 km. Therefore, the weight of the same object will be heavier at the poles and easiest at the equator. But even at these two points gravity on the Earth differs slightly. A small difference in the weight of the same object can be measured only with the help of spring scales.

And a completely different situation will develop in the conditions of other planets. For clarity, let's pay attention to Mars. The mass of the red planet is 9.31 times less terrestrial, and the radius is 1.88 times smaller. The first factor, respectively, should reduce the gravity on Mars in comparison with our planet by 9.31 times. At the same time, the second factor increases it by 3.53 times (1.88 in the square). As a result, the force of attraction on Mars is about a third of the earth's (3.53: 9.31 = 0.38). Accordingly, a rock with a mass on the Earth of 100 kg will weigh exactly 38 kg on Mars.

Given the gravity of the Earth, it can be compared in a single row between Uranus and Venus (which is less than 0.9 times Earth's gravity) and Neptune with Jupiter (their attraction is 1.14 and 2.3 times greater than ours). The smallest impact of gravitation was noted by Pluto - 15.5 times less than terrestrial conditions. But the strongest attraction is fixed on the Sun. It exceeds ours 28 times. In other words, a body weighing 70 kg on Earth would have been weighted to about 2 tons.

Under the lying layer water will leak

Another important creator and a one-time destroyer of reliefs - moving water. Its currents form a broad river valleys, canyons and gorges by its movement. However, even its small quantities with unhurried movement can form a ravine-beam relief in place of plains.

Punch their way through any obstacles - not the only side of the influence of currents. This external force also acts as a transporter of rock fragments. Thus, various relief formations are formed (for example, flat plains and outgrowth along rivers).

Specifically, the effect of flowing water affects the readily soluble rocks (limestone, chalk, gypsum, rock salt) located close to land. Rivers gradually remove them from their path, rushing into the depths of the earth's interior. This phenomenon is called karst, as a result of it new forms of relief are formed. Caves and funnels, stalactites and stalagmites, abysses and underground ponds - all this is the result of the long and powerful activity of the water masses.

Ice factor

Along with the flowing waters, glaciers take no less part in the destruction, transportation and deposition of rocks. Creating thereby new forms of relief, they smooth out the rocks, form moraine hills, ridges and hollows. The latter are often filled with water, turning into glacial lakes.

The destruction of rocks by means of glaciers is called an exhalation (glacial erosion). When penetrating into river valleys, ice exposes their bed and walls to strong pressure. Friable particles are ripped off, some of them freeze and thereby contribute to the expansion of the walls of the depth of the bottom. As a result, the river valleys take shape with the least resistance for ice advancement - the trough profile. Or, according to their scientific name, glacial troughs.

The melting of glaciers contributes to the creation of zandre - flat formations, consisting of sand particles accumulated in frozen water.

We are the external force of the Earth

Considering the internal forces acting on the Earth and external factors, it's time to mention also about us - those who have been bringing the colossal changes to the life of the planet for several decades already.

All forms of relief created by man are called anthropogenic (from the Greek anthropos - man, genesisum - origin, and Latin factor - matter). Today, the lion's share of this type of activity is carried out using modern technology. And new developments, research and impressive financial support from private / public sources ensure its rapid development. And this, in turn, constantly stimulates an increase in the rates of man's anthropogenic influence.

Especially subjected to changes in the plain. This area has always been a priority for settlement, construction of houses and infrastructure. Moreover, the practice of constructing embankments and artificial leveling of the relief became quite ordinary.

The environment is changing and for the purpose of mining. With the help of technology, people dig out huge open-cast mines, drill mines, make embankments in places of waste rock dumps.

Often the scale of human activity is comparable to that of natural processes. For example, modern technical achievements give us the opportunity to create huge channels. And for a much shorter time, if compared with the similar formation of river valleys by the flow of water.

The processes of destruction of the relief, called erosion, are greatly aggravated by human activity. First of all, the soil undergoes negative influence. This is facilitated by the plowing of slopes, rampant cutting of forests, excessive grazing of cattle, laying of pavement. Even more erosion is exacerbated by the growing pace of construction (especially in the construction of residential buildings, for which additional work is required, such as grounding, in which the earth's resistance is measured).

The last century was marked by the erosion of about a third of all the world's cultivated land. These processes were most widespread in large agricultural areas of Russia, the United States, China and India. Fortunately, the problem of land erosion is actively being solved at the international level. However, scientific research, new technologies and competent methods of their application by man will make the main contribution to reducing the harmful effect on the soil and recreating previously destroyed areas.