1 million years ago what happened. Dividing the history of the earth into eras and periods. The explosion that destroyed civilization

Late Proterozoic 650 million years ago.

The map depicts the breakup of the supercontinent Rodinia, which occurred 1,100 million years ago.

Cambrian:
The Cambrian period began approximately 570 million years ago, perhaps slightly earlier, and lasted 70 million years. This period began with an astonishing evolutionary explosion, during which representatives of most of the main groups of animals known to modern science first appeared on Earth. Across the equator stretched the huge continent of Gondwana, which included parts of modern Africa, South America, Southern Europe, the Middle East, India, Australia and Antarctica. In addition to Gondwana, there were four other smaller continents on the globe, located in what is now Europe, Siberia, China and North America (but together with northwestern Britain, western Norway and parts of Siberia). The North American continent of that time was known as Laurentia.
In that era, the climate on Earth was warmer than today. The tropical coasts of the continents were fringed by giant reefs of stromatolites, much like the coral reefs of modern tropical waters.

Ordovician. from 500 to 438 million years ago.

At the beginning of the Ordovician period, most of the southern hemisphere was still occupied by the great continent of Gondwana, while other large land masses were concentrated closer to the equator. Europe and North America (Laurentia) gradually moved away from each other, and the Iapetus Ocean expanded. At first, this ocean reached a width of about 2000 km, then began to narrow again as the land masses that make up Europe, North America and Greenland began to gradually approach each other until they finally merged into a single whole. Throughout the period, landmasses moved further and further south. Old Cambrian ice sheets melted and sea levels rose. Most of the land was concentrated in warm latitudes. At the end of the period, a new glaciation began. The end of the Ordovician was one of the coldest periods in the history of the earth. Ice covered most of the southern region of Gondwanna.

Silurian from 438 to 408 million years ago.

Gondwana moved towards the South Pole. The Iapetus Ocean was shrinking in size, and the landmasses forming North America and Greenland were moving closer together. They eventually collided, forming the giant supercontinent Laurasia. It was a period of violent volcanic activity and intense mountain building. It began with the Ice Age. As the ice melted, sea levels rose and the climate became milder.

Devonian. From 408 to 360 million years ago.

The Devonian period was a time of greatest cataclysms on our planet. Europe, North America and Greenland collided with each other, forming the huge northern supercontinent Laurasia. At the same time, huge masses of sedimentary rocks were pushed up from the ocean floor, forming huge mountain systems in eastern North America and western Europe. Erosion from rising mountain ranges has created large quantities of pebbles and sand. These formed extensive deposits of red sandstone. Rivers carried mountains of sediment into the sea. Vast swampy deltas were formed, which created ideal conditions for animals that dared to take the first, so important steps from water to land. Towards the end of the period, sea levels dropped. The climate has warmed and become more extreme over time, with alternating periods of heavy rainfall and severe drought. Vast areas of the continents became waterless.

Carbon. from 360 to 286 million years ago.
At the beginning of the Carboniferous period (Carboniferous), most of the earth's land was collected into two huge supercontinents: Laurasia in the north and Gondwana in the south. During the Late Carboniferous, both supercontinents steadily moved closer to each other. This movement pushed upward new mountain ranges that formed along the edges of the plates of the earth's crust, and the edges of the continents were literally flooded by streams of lava erupting from the bowels of the Earth. In the Early Carboniferous, shallow coastal seas and swamps spread over vast areas, and an almost tropical climate established over most of the land. Huge forests with lush vegetation significantly increased the oxygen content in the atmosphere. Subsequently, it became colder, and at least two major glaciations occurred on Earth.

Early Carboniferous.

Late Carboniferous

Permian. from 286 to 248 million years ago.

Throughout the Permian period, the supercontinents Gondwana and Laurasia gradually moved closer to each other. Asia collided with Europe, throwing up the Ural mountain range. India "ran over" into Asia - and the Himalayas arose. And in North America the Appalachians grew up. By the end of the Permian period, the formation of the giant supercontinent Pangea was completely completed. The Permian period began with glaciation, which caused a decrease in sea levels. As Gondwana moved north, the earth warmed up and the ice gradually melted. Laurasia became very hot and dry, and vast deserts spread across it.

Triassic
from 248 to 213 million years ago.

The Triassic period in Earth's history marked the beginning of the Mesozoic era, or the era of "middle life." Before him, all the continents were merged into a single giant supercontinent, Panagea. With the onset of the Triassic, Pangea again began to split into Gondwana and Laurasia, and the Atlantic Ocean began to form. Sea levels around the world were very low. The climate, almost everywhere warm, gradually became drier, and vast deserts formed in inland areas. Shallow seas and lakes evaporated intensely, causing the water in them to become very salty.

Jurassic period
from 213 to 144 million years ago.

By the beginning of the Jurassic period, the giant supercontinent Pangea was in the process of active disintegration. There was still a single vast continent south of the equator, which was again called Gondwana. Subsequently, it also split into parts that formed today's Australia, India, Africa and South America. The sea flooded a significant part of the land. Intensive mountain building took place. At the beginning of the period, the climate was warm and dry everywhere, then it became more humid.

Early Jurassic

Late Jurassic

Cretaceous period
144 to 65 million years ago

During the Cretaceous period, the “great split” of continents continued on our planet. The huge land masses that formed Laurasia and Gondwana gradually fell apart. South America and Africa moved away from each other, and the Atlantic Ocean became wider and wider. Africa, India and Australia also began to diverge in different directions, and giant islands eventually formed south of the equator. Most of the territory of modern Europe was then under water.
The sea flooded vast areas of land. The remains of hard-covered planktonic organisms formed huge thicknesses of Cretaceous sediments on the ocean floor. At first the climate was warm and humid, but then it became noticeably colder.

The Mesozoic-Cenozoic boundary 66 million years ago.

Eocene 55 to 38 million years ago.
During the Eocene, the main land masses began to gradually assume a position close to that which they occupy today. Much of the land was still divided into giant islands of sorts, as the huge continents continued to move away from each other. South America lost contact with Antarctica, and India moved closer to Asia. North America and Europe also split, and new mountain ranges emerged. The sea flooded part of the land. The climate was warm or temperate everywhere. Much of it was covered with lush tropical vegetation, and large areas were covered with dense swamp forests.

Miocene. from 25 to 5 million years ago.

During the Miocene, the continents were still “on the march”, and during their collisions a number of grandiose cataclysms occurred. Africa "crashed" into Europe and Asia, resulting in the appearance of the Alps. When India and Asia collided, the Himalayan mountains rose up. At the same time, the Rocky Mountains and Andes formed as other giant plates continued to shift and slide on top of each other.
However, Austria and South America remained isolated from the rest of the world, and each of these continents continued to develop its own unique fauna and flora. Ice cover in the southern hemisphere has spread throughout Antarctica, causing the climate to cool further.

Pleistocene. 2 to 0.01 million years ago

At the beginning of the Pleistocene, most continents occupied the same position as today, and some of them needed to cross half the globe to achieve this. A narrow land bridge connected North and South America. Australia was located on the opposite side of the Earth from Britain.
Giant ice sheets were creeping across the northern hemisphere. It was an era of great glaciation with alternating periods of cooling and warming and fluctuations in sea level. This ice age continues to this day.

Last Ice Age.

The world in 50 million years

The world in 150 million years

The world in 250 million years

The origin of life on Earth occurred about 3.8 billion years ago, when the formation of the earth's crust ended. Scientists have found that the first living organisms appeared in an aquatic environment, and only after a billion years did the first creatures emerge on the surface of the land.

The formation of terrestrial flora was facilitated by the formation of organs and tissues in plants and the ability to reproduce by spores. Animals also evolved significantly and adapted to life on land: internal fertilization, the ability to lay eggs, and pulmonary respiration appeared. An important stage in development was the formation of the brain, conditioned and unconditioned reflexes, and survival instincts. The further evolution of animals provided the basis for the formation of humanity.

Dividing the history of the Earth into eras and periods gives an idea of ​​the features of the development of life on the planet in different time periods. Scientists identify particularly significant events in the formation of life on Earth in separate periods of time - eras, which are divided into periods.

There are five eras:

• Archean;
• Proterozoic;
• Paleozoic;
• Mesozoic;
• Cenozoic.

The Archean era began about 4.6 billion years ago, when planet Earth was just beginning to form and there were no signs of life on it. The air contained chlorine, ammonia, hydrogen, the temperature reached 80°, the level of radiation exceeded permissible limits, under such conditions the origin of life was impossible.

It is believed that about 4 billion years ago our planet collided with a celestial body, and the consequence was the formation of the Earth’s satellite, the Moon. This event became significant in the development of life, stabilized the planet’s rotation axis, and contributed to the purification of water structures. As a result, the first life arose in the depths of the oceans and seas: protozoa, bacteria and cyanobacteria.

The Proterozoic era lasted from approximately 2.5 billion years ago to 540 million years ago. Remains of unicellular algae, mollusks, and annelids were discovered. Soil begins to form.

The air at the beginning of the era was not yet saturated with oxygen, but in the process of life, bacteria inhabiting the seas began to increasingly release O 2 into the atmosphere. When the amount of oxygen was at a stable level, many creatures took a step in evolution and switched to aerobic respiration.

The Paleozoic era includes six periods.

Cambrian period(530 - 490 million years ago) is characterized by the emergence of representatives of all species of plants and animals. The oceans were inhabited by algae, arthropods, and mollusks, and the first chordates (haikouihthys) appeared. The land remained uninhabited. The temperature remained high.

Ordovician period(490 – 442 million years ago). The first settlements of lichens appeared on land, and megalograptus (a representative of arthropods) began to come ashore to lay eggs. In the depths of the ocean, vertebrates, corals, and sponges continue to develop.

Silurian(442 – 418 million years ago). Plants come to land, and the rudiments of lung tissue form in arthropods. The formation of the bone skeleton in vertebrates is completed, and sensory organs appear. Mountain building is underway and different climatic zones are being formed.

Devonian(418 – 353 million years ago). The formation of the first forests, mainly ferns, is characteristic. Bone and cartilaginous organisms appear in reservoirs, amphibians began to come to land, and new organisms—insects—are formed.

Carboniferous period(353 – 290 million years ago). The appearance of amphibians, the subsidence of the continents, at the end of the period there was a significant cooling, which led to the extinction of many species.

Permian period(290 – 248 million years ago). The earth is inhabited by reptiles; therapsids, the ancestors of mammals, appeared. The hot climate led to the formation of deserts, where only hardy ferns and some conifers could survive.

The Mesozoic era is divided into 3 periods:

Triassic(248 – 200 million years ago). Development of gymnosperms, appearance of the first mammals. The split of land into continents.

Jurassic period(200 - 140 million years ago). The emergence of angiosperms. The appearance of the ancestors of birds.

Cretaceous period(140 – 65 million years ago). Angiosperms (flowering plants) became the dominant group of plants. Development of higher mammals, true birds.

The Cenozoic era consists of three periods:

Lower Tertiary period or Paleogene(65 – 24 million years ago). The disappearance of most cephalopods, lemurs and primates appear, later parapithecus and dryopithecus. The development of the ancestors of modern mammal species - rhinoceroses, pigs, rabbits, etc.

Upper Tertiary period or Neogene(24 – 2.6 million years ago). Mammals inhabit land, water, and air. The appearance of Australopithecines - the first ancestors of humans. During this period, the Alps, Himalayas, and Andes were formed.

Quaternary or Anthropocene(2.6 million years ago – today). A significant event of the period was the appearance of man, first the Neanderthals, and soon Homo sapiens. The flora and fauna acquired modern features.

One of the curves showing sea level fluctuations over the past 18,000 years (the so-called eustatic curve). In the 12th millennium BC. sea ​​level was about 65 m lower than today, and in the 8th millennium BC. - already at less than 40 m. The rise in level occurred quickly, but unevenly. (According to N. Morner, 1969)

The sharp drop in sea level was associated with the widespread development of continental glaciation, when huge masses of water were withdrawn from the ocean and concentrated in the form of ice in the high latitudes of the planet. From here, glaciers slowly spread towards the middle latitudes in the northern hemisphere on land, in the southern hemisphere - along the sea in the form of ice fields that overlapped the shelf of Antarctica.

It is known that in the Pleistocene, the duration of which is estimated at 1 million years, three phases of glaciation are distinguished, called in Europe Mindel, Ries and Würm. Each of them lasted from 40-50 thousand to 100-200 thousand years. They were separated by interglacial eras, when the climate on Earth became noticeably warmer, approaching the modern one. In some episodes it became even 2-3° warmer, which led to the rapid melting of ice and the release of vast areas on land and in the ocean. Such dramatic climate changes were accompanied by equally dramatic fluctuations in sea level. During the era of maximum glaciation, it decreased, as already mentioned, by 90-110 m, and during interglacial periods it increased to +10... 4-20 m compared to the current one.

The Pleistocene is not the only period during which significant fluctuations in sea levels occurred. Essentially, they mark almost all geological epochs in the history of the Earth. Sea level has been one of the most unstable geological factors. Moreover, this has been known for quite a long time. After all, ideas about transgressions and regressions of the sea were developed back in the 19th century. And how could it be otherwise, if in many sections of sedimentary rocks on platforms and in mountainous folded areas, clearly continental sediments are replaced by marine ones and vice versa. Sea transgression was judged by the appearance of remains of marine organisms in the rocks, and regression was judged by their disappearance or the appearance of coals, salts or red flowers. By studying the composition of faunal and floristic complexes, they determined (and are still determining) where the sea came from. The abundance of thermophilic forms indicated the invasion of waters from low latitudes, the predominance of boreal organisms indicated transgression from high latitudes.

The history of each specific region had its own series of transgressions and regressions of the sea, since it was believed that they were caused by local tectonic events: the invasion of sea waters was associated with the subsidence of the earth's crust, their departure with its uplifting. When applied to the platform regions of the continents, on this basis a theory of oscillatory movements was even created: cratons either sank or rose in accordance with some mysterious internal mechanism. Moreover, each craton obeyed its own rhythm of oscillatory movements.

It gradually became clear that transgressions and regressions in many cases occurred almost simultaneously in different geological regions of the Earth. However, inaccuracies in paleontological dating of certain groups of layers did not allow scientists to come to a conclusion about the global nature of most of these phenomena. This conclusion, unexpected for many geologists, was made by American geophysicists P. Weil, R. Mitchum and S. Thompson, who studied seismic sections of the sedimentary cover within the continental margins. Comparison of sections from different regions, often very distant from one another, helped to reveal the confinement of many unconformities, breaks, accumulation or erosional forms to several time ranges in the Mesozoic and Cenozoic. According to these researchers, they reflected the global nature of ocean level fluctuations. The curve of such changes, constructed by P. Weil et al., makes it possible not only to identify epochs of high or low standing, but also to estimate, of course to a first approximation, their scale. As a matter of fact, this curve summarizes the work experience of geologists of many generations. Indeed, you can learn about the Late Jurassic and Late Cretaceous transgressions of the sea or its retreat at the Jurassic-Cretaceous boundary, in the Oligocene and Late Miocene, from any textbook on historical geology. What was new, perhaps, was that these phenomena were now associated with changes in the level of ocean waters.

The scale of these changes was surprising. Thus, the most significant marine transgression, which flooded most of the continents in Cenomanian and Turonian times, is believed to have been caused by a rise in the level of ocean waters by more than 200-300 m above the modern one. The most significant regression that occurred in the Middle Oligocene is associated with a drop in this level by 150-180 m below the modern one. Thus, the total amplitude of such fluctuations in the Mesozoic and Cenozoic was almost 400-500 m! What caused such enormous fluctuations? They cannot be attributed to glaciations, since during the late Mesozoic and the first half of the Cenozoic the climate on our planet was exceptionally warm. However, many researchers still associate the mid-Oligocene minimum with the onset of a sharp cooling in high latitudes and with the development of the glacial shell of Antarctica. However, this alone was probably not enough to reduce the sea level by 150 m at once.

The reason for such changes was tectonic restructuring, which entailed a global redistribution of water masses in the ocean. Now we can only offer more or less plausible versions to explain fluctuations in its level in the Mesozoic and Early Cenozoic. Thus, analyzing the most important tectonic events that occurred at the turn of the Middle and Late Jurassic; as well as the Early and Late Cretaceous (which are associated with a long rise in water levels), we find that it was these intervals that were marked by the opening of large oceanic depressions. The Late Jurassic saw the emergence and rapid expansion of the western arm of the ocean, the Tethys (the region of the Gulf of Mexico and the Central Atlantic), and the end of the Early Cretaceous and most of the Late Cretaceous eras were marked by the opening of the southern Atlantic and many trenches of the Indian Ocean.

How could the formation and spreading of the bottom in young ocean basins affect the position of the water level in the ocean? The fact is that the depth of the bottom in them at the first stages of development is very insignificant, no more than 1.5-2 thousand m. The expansion of their area occurs due to a corresponding reduction in the area of ​​ancient oceanic reservoirs, which are characterized by a depth of 5-6 thousand. m, and in the Benioff zone, areas of the bed of deep-sea abyssal basins are absorbed. The water displaced from disappearing ancient basins raises the overall ocean level, which is recorded in land sections of the continents as sea transgression.

Thus, the breakup of continental megablocks should be accompanied by a gradual rise in sea level. This is exactly what happened in the Mesozoic, during which the level rose by 200-300 m, and perhaps more, although this rise was interrupted by eras of short-term regressions.

Over time, the bottom of young oceans became deeper and deeper as the new crust cooled and its area increased (the Slater-Sorokhtin law). Therefore, their subsequent opening had much less influence on the position of the ocean water level. However, it would inevitably lead to a reduction in the area of ​​the ancient oceans and even to the complete disappearance of some of them from the face of the Earth. In geology, this phenomenon is called the “collapsing” of the oceans. It is realized in the process of the rapprochement of continents and their subsequent collision. It would seem that the slamming of ocean basins should cause a new rise in water levels. In fact, the opposite happens. The point here is a powerful tectonic activation that covers converging continents. Mountain-building processes in the zone of their collision are accompanied by a general uplift of the surface. In the marginal parts of the continents, tectonic activation manifests itself in the collapse of blocks of the shelf and slope and their lowering to the level of the continental foot. Apparently, these subsidences also cover adjacent areas of the ocean floor, as a result of which it becomes much deeper. The overall level of ocean waters is falling.

Since tectonic activation is a one-act event and covers a short period of time, the drop in level occurs much faster than its increase during spreading of young oceanic crust. This is precisely what can explain the fact that sea transgressions on the continent develop relatively slowly, while regressions usually occur abruptly.

Map of possible flooding of Eurasian territory at various values ​​of the probable rise in sea level. The scale of the disaster (with the sea level expected to rise by 1 m during the 21st century) will be much less noticeable on the map and will have almost no impact on the lives of most countries. The areas of the coasts of the North and Baltic Seas and southern China are enlarged. (The map can be enlarged!)

Now let's look at the issue of AVERAGE SEA LEVEL.

Surveyors leveling on land determine the height above “mean sea level.” Oceanographers who study sea level fluctuations compare them with elevations on the shore. But, alas, even the “long-term average” sea level is far from a constant value and, moreover, is not the same everywhere, and the sea coasts rise in some places and fall in others.

An example of modern land subsidence is the coasts of Denmark and Holland. In 1696, in the Danish city of Agger, there was a church 650 m from the shore. In 1858, the remains of this church were finally swallowed up by the sea. During this time, the sea advanced on land at a horizontal speed of 4.5 m per year. Now on the western coast of Denmark, the construction of a dam is being completed, which should block the further advance of the sea.

The low-lying coasts of Holland are exposed to the same danger. The heroic pages of the history of the Dutch people are not only the struggle for liberation from Spanish rule, but also an equally heroic struggle against the advancing sea. Strictly speaking, here the sea does not advance so much as the sinking land recedes before it. This can be seen from the fact that the average high water level on the island. The Nordstrand in the North Sea rose by 1.8 m from 1362 to 1962. The first benchmark (altitude mark above sea level) was made in Holland on a large, specially installed stone in 1682. From the 17th to the mid-20th century, The soil subsidence on the Dutch coast occurred at an average rate of 0.47 cm per year. Now the Dutch are not only defending the country from the advance of the sea, but also reclaiming the land from the sea by building grandiose dams.

There are, however, places where the land rises above the sea. The so-called Fenno-Scandinavian shield, after being freed from the heavy ice of the Ice Age, continues to rise in our time. The coast of the Scandinavian Peninsula in the Gulf of Bothnia is rising at a rate of 1.2 cm per year.

Alternating lowering and rising of coastal land is also known. For example, the shores of the Mediterranean Sea sank and rose in places by several meters even in historical times. This is evidenced by the columns of the Temple of Serapis near Naples; marine elasmobranch molluscs (Pholas) have made passages in them to the height of human height. This means that from the time the temple was built in the 1st century. n. e. the land sank so much that part of the columns was immersed in the sea, and probably for a long time, since otherwise the mollusks would not have had time to do so much work. Later, the temple with its columns again emerged from the waves of the sea. According to 120 observation stations, over 60 years the level of the entire Mediterranean Sea has risen by 9 cm.

Climbers say: “We stormed a peak so many meters above sea level.” Not only surveyors and climbers, but also people completely unrelated to such measurements are accustomed to the concept of height above sea level. It seems to them unshakable. But, alas, this is far from the case. Ocean levels are constantly changing. It is fluctuated by tides caused by astronomical reasons, wind waves excited by the wind, and changeable like the wind itself, wind surges and water surges off the coast, changes in atmospheric pressure, the deflecting force of the Earth's rotation, and finally, the heating and cooling of ocean water. In addition, according to the research of Soviet scientists I.V. Maksimov, N.R. Smirnov and G.G. Khizanashvili, the ocean level changes due to episodic changes in the speed of rotation of the Earth and movement of its axis of rotation.

If you heat only the top 100 m of ocean water by 10°, the sea level will rise by 1 cm. Heating the entire thickness of ocean water by 1° raises its level by 60 cm. Thus, due to summer warming and winter cooling, sea level in the middle and high latitudes subject to noticeable seasonal fluctuations. According to the observations of the Japanese scientist Miyazaki, the average sea level off the western coast of Japan rises in the summer and falls in the winter and spring. The amplitude of its annual fluctuations is from 20 to 40 cm. The level of the Atlantic Ocean in the northern hemisphere begins to rise in the summer and reaches a maximum in winter; in the southern hemisphere, its reverse trend is observed.

The Soviet oceanographer A. I. Duvanin distinguished two types of fluctuations in the level of the World Ocean: zonal, as a result of the transfer of warm waters from the equator to the poles, and monsoon, as a result of prolonged surges excited by monsoon winds that blow from the sea to land in the summer and in in the opposite direction in winter.

A noticeable slope of sea level is observed in areas covered by ocean currents. It is formed both in the direction of the flow and across it. The transverse slope at a distance of 100-200 miles reaches 10-15 cm and changes along with changes in current speed. The reason for the transverse inclination of the flow surface is the deflecting force of the Earth's rotation.

The sea also noticeably reacts to changes in atmospheric pressure. In such cases, it acts as an “inverted barometer”: more pressure means lower sea level, less pressure means higher sea level. One millimeter of barometric pressure (more precisely, one millibar) corresponds to one centimeter of sea level height.

Changes in atmospheric pressure can be short-term and seasonal. According to the research of the Finnish oceanologist E. Lisitsyna and the American one J. Patullo, level fluctuations caused by changes in atmospheric pressure are isostatic in nature. This means that the total pressure of air and water on the bottom in a given section of the sea tends to remain constant. Heated and rarefied air causes the level to rise, cold and dense air causes the level to fall.

It happens that surveyors conduct leveling along the seashore or overland from one sea to another. Having arrived at the final destination, they discover a discrepancy and begin to look for the error. But in vain they rack their brains - there may not be a mistake. The reason for the discrepancy is that the level surface of the sea is far from equipotential. For example, under the influence of prevailing winds between the central part of the Baltic Sea and the Gulf of Bothnia, the average difference in level, according to E. Lisitsyna, is about 30 cm. Between the northern and southern parts of the Gulf of Bothnia, at a distance of 65 km, the level changes by 9.5 cm. Between On both sides of the English Channel the difference in level is 8 cm (Creese and Cartwright). The slope of the sea surface from the Channel to the Baltic, according to Bowden's calculations, is 35 cm. The level of the Pacific Ocean and the Caribbean Sea at the ends of the Panama Canal, which is only 80 km long, differs by 18 cm. In general, the level of the Pacific Ocean is always slightly higher than the level of the Atlantic. Even if you move along the Atlantic coast of North America from south to north, a gradual rise in level of 35 cm is found.

Without dwelling on the significant fluctuations in the level of the World Ocean that occurred in past geological periods, we will only note that the gradual rise in sea level, which was observed throughout the 20th century, averages 1.2 mm per year. It is apparently caused by the general warming of the climate of our planet and the gradual release of significant masses of water that had been bound by glaciers until that time.

So, neither oceanographers can rely on the marks of surveyors on land, nor surveyors on the readings of tide gauges installed off the coast at sea. The level surface of the ocean is far from an ideal equipotential surface. Its exact definition can be achieved through the joint efforts of geodesists and oceanologists, and even then not before at least a century of simultaneous observations of vertical movements of the earth’s crust and sea level fluctuations at hundreds, even thousands of points have been accumulated. In the meantime, there is no “average level” of the ocean! Or, what is the same thing, there are many of them - each point has its own shore!

Philosophers and geographers of hoary antiquity, who had to use only speculative methods for solving geophysical problems, were also very interested in the problem of ocean level, although in a different aspect. We find the most specific statements on this matter in Pliny the Elder, who, by the way, shortly before his death while observing the eruption of Vesuvius, wrote rather arrogantly: “There is nothing in the ocean at present that we cannot explain.” So, if we discard the disputes of Latinists about the correctness of the translation of some of Pliny’s arguments about the ocean, we can say that he considered it from two points of view - the ocean on a flat Earth and the ocean on a spherical Earth. If the Earth is round, Pliny reasoned, then why don’t the waters of the ocean on its reverse side flow into the void; and if it is flat, then for what reason the ocean waters do not flood the land, if everyone standing on the shore can clearly see the mountain-like bulge of the ocean, behind which ships are hidden on the horizon. In both cases he explained it this way; water always tends to the center of the land, which is located somewhere below its surface.

The problem of sea level seemed insoluble two thousand years ago and, as we see, remains unresolved to this day. However, the possibility cannot be ruled out that the features of the level surface of the ocean will be determined in the near future by geophysical measurements made using artificial Earth satellites.

Gravity map of the Earth compiled by the GOCE satellite.
These days …

Oceanologists re-examined the already known data on sea level rise over the past 125 years and came to an unexpected conclusion - if throughout almost the entire 20th century it rose noticeably slower than we previously thought, then in the last 25 years it has grown at a very rapid pace, says the paper. article published in the journal Nature.

A group of researchers came to such conclusions after analyzing data on fluctuations in the levels of the Earth's seas and oceans during high and low tides, which have been collected in different parts of the planet using special tide gauge instruments for a century. Data from these instruments, as scientists note, are traditionally used to estimate sea level rise, but this information is not always absolutely accurate and often contains large time gaps.

“These averages do not reflect how the sea actually grows. Tire gauges are usually located along the coast. Because of this, large areas of the ocean are not included in these estimates, and if they are included, they usually contain large “holes,” Carling Hay from Harvard University (USA) is quoted in the article.

As another author of the article, Harvard oceanographer Eric Morrow, adds, until the early 1950s, humanity did not conduct systematic observations of sea levels at the global level, which is why we have almost no reliable information about how quickly the global sea level was rising. ocean in the first half of the 20th century.

Our planet is more than 4.5 billion years old. At the moment it appeared, it looked completely different. What happened in ancient times on the territory of modern Russia, and how it changed over the years - in the book “Ancient Monsters of Russia”.

3000 million years ago

In the first millions of years of its life, the Earth was like hell. There was constant acid rain here, and hundreds of volcanoes erupted. There were many more asteroids. Endless meteorite showers formed the planet - they crashed and became part of it. Some meteorites reached the size of modern cities.

One day, the Earth collided with another planet, one part of which joined us, and the second flew into orbit and over the years turned into the modern Moon.

Illustration from the book

3 billion years ago, a day lasted only 5 hours, and there were 1500 days in a year. A lunar eclipse occurred once every 50 hours, and a solar eclipse occurred once every 100 hours. It probably looked very beautiful, but there was no one yet to admire natural phenomena.