The movement of the earth

1. Earthquake

2. Volcanic eruption

3. Debris flow

4. Soil erosion

5. landslides

6.tornado

7. Typhoon

8.tsunami

9. Long live

10. Storm surge

1 1. Biological disaster

12. Drought

13. Flooding

14. Cold wave

15. Blizzard

16. sandstorm

It was not until the Copernican era of16th century that people realized that the earth was just a planet.

Of course, the earth can be observed without flying machines, but we didn't have a map of the whole earth until the twentieth century. Photos taken from space should be of certain importance; For example, they are very helpful to weather forecast and storm tracking forecast. How beautiful they are!

Due to different chemical composition and seismic properties, the earth is divided into different rock formations (depth-km);

0- 40 shell

40- 400 upper mantle-upper mantle

400- 650 transition zone-transition zone

650-2700 lower mantle-lower mantle

2700-2890 D layer -D layer

2890-5 150 outer core-outer core

5 150-6378 kernel-kernel

The thickness of the earth's crust is different, the ocean is thin and the mainland is thick. The core and crust are entities; The outer core and mantle are fluids. Different layers are separated by discontinuous sections which are obtained from seismic data. One of the most famous is the Moho surface between the crust and the upper mantle.

Most of the mass of the earth is concentrated in the mantle, and most of the rest is in the core; We live only a small part of the whole (the following values are × 10E24kg):

Atmosphere = 0.000005 1

Ocean = 0.00 14

Shell = 0.026

Mantle = 4.043

Outer core = 1.835

Inland nuclear = 0.09675

The core may be mostly composed of iron (or nickel/iron), although it may also be some lighter substances. The temperature in the center of the earth's core may be as high as 7500K, which is hotter than the surface of the sun. The lower mantle may be composed of silicon, magnesium, oxygen and some iron, calcium and aluminum. The upper mantle is mainly composed of olivine, pyroxene (iron/magnesium silicate), calcium and aluminum. We know that these metals come from earthquakes; Samples of the upper mantle reach the surface, just like volcanoes spewing magma, but most of the earth is still inaccessible. The crust is mainly composed of quartz (silica) and other feldspar-like silicates. Generally speaking, the chemical elements of the earth are as follows:

34.6% iron

29.5% oxygen

15.2% silicon

12.7% magnesium

2.4% nickel

1.9% sulfur

0.05% titanium

The earth is the densest star in the solar system.

Other terrestrial planets may have similar structures and material compositions, but there are also some differences: the moon has at least one small core; Mercury has an oversized core (equivalent to its diameter); The mantle of Mars and the moon is much thicker; The moon and mercury may not have a crust composed of different chemical elements; The earth may be the only earth-like planet with an inner core and an outer core. It is worth noting that our theory about the internal structure of planets only applies to the earth.

Unlike other terrestrial planets, the earth's crust consists of several solid plates, each of which floats on the hot mantle. It is called plate theory in theory. It is described as having two processes: expansion and contraction. When the two plates move away from each other and the magma below forms a new crust, it will expand. Shrinkage occurs when two plates collide with each other, and the edge of one plate extends below the other plate and is destroyed by heat in the hot mantle. There are many faults at the plate boundary (such as the San Andreas fault in California), and there are also collisions between continental plates (such as the Indian Ocean plate and the Eurasian plate). At present, there are eight main departments:

North American Plate-North America, Northwest Atlantic and Greenland

South American Plate-South America and Southwest Atlantic Ocean

Antarctica plate-Antarctica and its coast

Asia-Europe Plate-Northeast Atlantic, Europe and Asia except India.

Africa Plate-Africa, Southeast Atlantic and Western Indian Ocean

India and Australia Plate-India, Australia, New Zealand and most of the Indian Ocean.

Nazca Plate-Adjacent parts of the East Pacific and South America

Pacific Plate-Most of the Pacific Ocean (and the southern coast of California)

There are more than 20 small plates, such as Arabic and Filipino plates. Earthquakes often occur at the junction of these plates. Drawing a map can make it easier to see the plate boundaries (above).

The surface of the earth is very young. In a short period of 5 billion years (astronomical standard), the process of erosion and tectonic movement has been repeated, and most of the earth's surface has been formed and destroyed again and again, thus removing most of the original geographical traces (such as craters caused by the impact of stars). In this way, the early history of the earth was cleared. The earth has existed for 4.5 to 4.6 billion years, but the oldest known stones are only 4 billion years old, and there are only a handful of stones over 3 billion years old. The earliest biological fossils are less than 3.9 billion years old. There is no exact record of the moment when life really begins. 0% of the earth's surface is covered with water. The earth is the only planet that can have liquid water on its surface (although there are liquid ethane and methane on Titan's surface, and there is also liquid water underground on Europa). We know that liquid water is an important condition for life. The heat capacity of the ocean is also an important condition to keep the earth's temperature relatively stable. Liquid water has also caused surface erosion and continental climate diversification, which is a unique process in the solar system (it may have happened on Mars a long time ago).

The earth's atmosphere is composed of 77% nitrogen, 2 1% oxygen and trace amounts of argon, carbon dioxide and water. When the earth was first formed, there may be a lot of carbon dioxide in the atmosphere, but almost all of it is combined into carbonate rocks, and a small part is dissolved in the ocean or consumed by living plants. At present, plate tectonics and biological activities maintain the continuous flow of carbon dioxide in the atmosphere to other places and back. A small amount of stable carbon dioxide in the atmosphere is of great significance to maintain the surface temperature through the greenhouse effect. The greenhouse effect increased the average surface temperature by 35℃ (from -2 1℃ in freezing to1℃ in human). Without it, the ocean will freeze and life will be impossible.

From a chemical point of view, the existence of a large amount of oxygen is very obvious. Oxygen is a very active gas, which is easy to combine with other substances quickly in general environment. The generation and maintenance of oxygen in the earth's atmosphere is completed by biological activities. Without life, there is not enough oxygen.

The interaction between the earth and the moon slows down the rotation speed of the earth by 2 milliseconds every century. The current survey shows that about 900 million years ago, there were 48 1 day and 18 hours in a year.

The earth has a medium magnetic field formed by the core current. Due to the interaction of solar wind, the aurora phenomenon is caused by the earth's magnetic field and the upper atmosphere of the earth (see interplanetary medium). The uncertain period of these factors also leads to the relative movement of magnetic poles on the surface; The North Magnetic Pole is now in northern Canada.

[Edit this paragraph] Earth satellite

The moon is commonly known as the moon, also known as the Moon. It is the only natural satellite in the solar system. The moon is the most obvious example of a natural satellite. In the solar system, except Mercury and Venus, other planets have natural satellites. The moon is about 4.6 billion years old. The moon has a layered structure such as shell, mantle and core. The average thickness of the outermost lunar shell is about 60-65 kilometers. Below the lunar crust 1000 km is the lunar mantle, which occupies most of the moon's volume. Below the moon's mantle is the moon's core, whose temperature is about 1000 degrees, which is likely to be in a molten state. The moon is about 3476 kilometers in diameter, which is 1/4 of the earth. The volume is only 1/49 of the earth's, and the mass is about 735 billion tons, which is equivalent to 1/8 1 of the earth's mass. The gravity on the surface of the moon is almost 1/6 of that of the earth.

There are dark parts and bright areas on the surface of the moon. When early astronomers observed the moon, they thought that the dark area was covered by seawater, so they called it "sea". The more famous ones are the sea of clouds, the wet sea and the sea of tranquility. The bright part is the mountains, where mountains are stacked and criss-crossed, and craters are dotted. Bailey Crater is located near the South Pole, with a diameter of 295 kilometers, which can hold the whole Hainan Island. The deepest mountain is Newton crater, which is 8788 meters deep. Besides craters, there are ordinary mountains on the moon. Mountains and valleys overlap, giving you a unique perspective.

The front of the moon always faces the earth. On the other hand, except for the area near the edge of the moon, which is visible in the middle due to Libra movement, most areas on the back of the moon are invisible from the earth. In the era without detectors, the back of the moon has always been an unknown world. A major feature of the back of the moon is that there are almost no dark lunar surface features such as the moon and the sea. When the artificial probe runs to the back of the moon, it will not be able to communicate directly with the earth.

The moon revolves around the earth for about one lunar month, and moves half a degree relative to the background starry sky every hour, which is similar to the apparent diameter of the moon. Unlike other satellites, the orbital plane of the moon is closer to the ecliptic plane than the equatorial plane of the earth.

Relative to the background starry sky, the time required for the moon to go around the earth (the moon makes one revolution) is called sidereal month; The time between the new moon and the next one (or the time between two identical moon phases) is called the new moon. The reason why Wang Shuo's moon is longer than that of the star moon is that during the earth's operation on the moon, it moved forward a certain distance in its orbit around the sun.

Because the rotation period of the moon is exactly the same as its period of revolution, the earth can only see that the moon always faces the earth with the same face. From the early days of the formation of the moon, the earth was affected by a moment, which led to the slow rotation speed. This process is called tidal locking. Therefore, part of the angular momentum of the earth's rotation is converted into the angular momentum of the moon's revolution around the earth. As a result, the moon is far away from the earth at a speed of about 38 mm per year. At the same time, the earth's rotation is getting slower and slower, and the length of a day is getting longer every year 15 microsecond.

The gravity exerted by the moon on the earth is one of the reasons for the tidal phenomenon. The orbit of the moon around the earth is synchronous, and the so-called synchronous rotation is not strict. Because the orbit of the moon is elliptical, when the moon is at perihelion, its rotation speed can't keep up with the revolution speed, so we can see that the eastern part of the moon reaches 98 degrees east longitude. On the contrary, when the moon is at apohelion, its rotation speed is faster than its revolution speed, so we can see that the western part of the moon passes through 98 degrees Darcy. This phenomenon is called meridian libration.

Strictly speaking, the earth and the moon revolve around a concentric center, which is 4,700 kilometers away from the center of the earth (2/3 of radius of the earth's). Because the center of homogeneity is below the surface, the movement of the earth around the center of homogeneity seems to be "shaking". Seen from above the North Pole of the Earth, both the Earth and the Moon rotate clockwise. Moreover, the moon is also clockwise around the earth; Even the earth moves clockwise around the sun.

Many people don't understand why the inclination of the moon's orbit and the inclination of the moon from the axis change so much. In fact, the orbital inclination is relative to the central celestial body (the earth), from the axial inclination to the satellite.

The orbit plane of the moon (ecliptic plane) keeps an included angle of 5. 145396 with the ecliptic plane (earth's orbit plane), while the rotation axis of the moon forms an included angle of 1.5424 with the normal of the ecliptic plane. Because the earth is not a perfect sphere, but bulges at the equator, the white road surface keeps precessing (that is, the intersection with the ecliptic rotates clockwise) and completes one week every 6793.5 days (18.5966). During this period, the angle between the white plane and the equatorial plane of the earth (the equatorial plane of the earth inclines to the ecliptic plane at 23.45) will change from 28.60 (i.e. 23.45+5. 15) to18.30 (i.e. 23.45-5. 15). Similarly, the angle between the rotation axis of the moon and the white plane will be between 6.69 (that is, 5. 15+ 1.54) and 3.60 (that is, 5. 15- 1.54). These changes in the lunar orbit will in turn affect the inclination of the earth's rotation axis, making it swing by 0.002 56, which is called nutation.

The two intersections between the ecliptic plane and the ecliptic plane are called the lunar intersection-the ascending intersection (north point) refers to the point where the moon passes to the north of the ecliptic plane; Descending node (South Point) refers to the point where the moon passes south of the ecliptic. When the new moon is just at the intersection of the moon, a solar eclipse will occur; An eclipse occurs when the full moon is just at the intersection of the moons.

The structure on the back of the moon is quite different from that on the front. The Moon Sea occupies less land and there are many craters. The terrain is uneven, and the longest and shortest radius of the moon are located on the back. Some places are 4 kilometers longer than the average radius of the moon, and some places are 5 kilometers shorter (such as Van der Graf depression). No "lump" was found on the back. The moon shell on the back is thicker than that on the front, with the thickest point reaching 150km, while the thickness of the moon shell on the front is only about 60km.

The moon itself does not shine, but reflects sunlight. The brightness of the moon varies with the angular distance between the sun and the moon and the distance between the earth and the moon. The average brightness is 1/465000 of the brightness of the sun, and the brightness varies from 1/630000 to 1/375000. At the full moon, the average brightness is-12.7 (see). Its average illumination to the earth is 0.22 lux, which is equivalent to the illumination of 100 watt electric lamp at a distance of 2 1 meter. The surface of the moon is not a good reflector. Its average albedo is only 7%, and the other 93% is absorbed by the moon. The albedo of Guangdong Sea is even lower, about 6%. The albedo of the lunar highlands and craters is 17%, and it seems that the mountains are brighter than the moon sea. The brightness of the moon also changes. The following table lists the brightness values of different months with full moon brightness of 100. It can be seen that the brightness of the full moon is more than ten times that of the upper and lower chords.

Because there is no atmosphere on the moon, the heat capacity and thermal conductivity of lunar materials are very low, so the temperature difference between day and night on the surface of the moon is very large. During the day, the temperature where the sun shines vertically is as high as+127℃; The temperature can be reduced to-183℃ at night. These values only represent the temperature on the surface of the moon. The temperature of lunar soil can be measured by radio observation. This measurement shows that the temperature in the deeper part of the lunar soil rarely changes, which is precisely due to the low thermal conductivity of lunar material.

From the propagation of lunar seismic waves, we know that the moon also has layered structures such as shell, mantle and core. The outermost lunar shell is 60 ~ 65km thick. Under the lunar crust to the depth of 1000 km is the lunar mantle, which accounts for most of the lunar volume. Below the lunar mantle is the lunar core. The temperature of the lunar nucleus is about 1000℃, which is probably in a molten state. It is speculated that it may be composed of iron, nickel, sulfur and eclogite.

[Edit this paragraph] The cosmic environment of the earth.

The earth belongs to the solar system of the Milky Way. It lies between Venus and Mars. It is the third closest planet to the sun in the solar system. There is a satellite. So far, the earth is the only living planet.

The cosmic environment in which the earth is located refers to the cosmic environment centered on the earth, which can be understood from both macro and micro levels. Macroscopically, it refers to the position of the earth in the celestial system, that is, the earth-moon system-solar system-galaxy-total galaxy; Microscopically, it refers to the position of the earth in the solar system. In the infinite space, the earth is just a drop in the ocean, in an endless movement.

[Edit this paragraph] The internal environment of the earth

Animals that have long been extinct on the ground, is there really a paradise inside the earth?

As far back as 1904, a miner named Brown in the Caster Mountains of California, USA, discovered an artificial tunnel similar to the giant's residence. There are huge houses locked by huge copper in the cave. There are shields made of gold and things that have never been seen before, and strange pictures and documents are painted on the walls.

During World War II, American Army soldier Eber was separated from his comrades-in-arms in the battle with Japanese invaders and left in the forest. One day, he came across a hole hidden by a boulder. Herb ventured into the cave, only to find that it was as bright as day by artificial light source, just like a huge underground city. Eber was shocked when he was suddenly caught. Four years later, he tried to escape. According to him, this underground kingdom has seven tunnels leading to the ground, and there are secret entrances and exits in other parts of the world.

1968 65438+ 10 The exploration team of American TG Oil Company found a deep underground rock tunnel 270 meters underground in the cave in western Turkey, with a height of about 4-5 meters and a smooth and bright top, which was obviously artificially polished. There are cobweb-shaped horizontal holes everywhere in the cave, just like a confusing maze.

Coincidentally, one summer night a few years ago, a bright light was emitted in a cave halfway up the mountain near Longgong, Anshun County, Guizhou Province, China. The beam was barrel-shaped, walked 4 meters straight, swept 500 meters across the field, and went straight to the opposite hillside, illuminating the surrounding villages and fields for several minutes. According to local county records, this wonder happened during the Shunzhi period of the Qing Dynasty. However, the locals in that cave are very familiar with it. There is nothing in the cave, so where does the strong light come from?

Some people may ask, if this underground kingdom really exists, why don't they return to sunny ground life? There seems to be only one answer: the residents of this underground kingdom have lived underground for a long time, or have evolved into thermophilic silicon life bodies, and it is impossible to adapt to life on the ground.

One thing is certain, if the underground kingdom really exists, then they must have mastered higher technology than the surface, and it is not difficult to get answers to a series of so-called mysteries such as flying saucers. Not to mention whether there is really an underground kingdom, is the interior of the earth really empty? Many geophysicists believe that the existing weight of the earth is one million times that of 6 trillion tons. If the earth's interior is not empty, its weight should be much more than that.

The underground kingdom theory has triggered a fierce debate in the scientific community on the theory that the earth is empty, and the result can only be seen. But it inspires us on the surface that when the earth's climate changes suddenly or other surface disasters occur, it may be more practical for us to hide underground on the surface than to emigrate to other planets.

[Edit this paragraph] The relationship between the earth and population

Judging from the relationship between resources and human beings, the relationship between environment and human beings, the population on the earth is limited in number: population = the area suitable for human habitation/the site needed by individuals for production and life. Expressed by the formula: X =S/s=aS. Where x is the population, s is the area suitable for human habitation, s is the site needed by each individual for production and life, and a= 1/s is a constant. The above formula X=aS can be called the law of population.

From the perspective of production and life, the space required for each individual's production and life is 1500 square meters. The upper limit of the earth's population can be calculated from the formula of population law X=aS, and the area suitable for human habitation and the site required for each individual's production and life on the earth are 1500 square meters.

Modern census refers to the investigation and registration of the national population by households within the time specified by the state in accordance with unified items, unified forms and unified reporting methods. It is a large-scale social survey with strict organization and leadership, careful planning and scientific methods. The United States began to conduct a census from 1790, and was the first country to conduct a census.

There are 36 items in the United Nations census, including population migration, family, fertility rate, mortality rate, education, economy, housing and other characteristics. Some countries have more census items. For example, there are 65 items in US/KOOC-0/980, 69 items in Canada/KOOC-0/98/KOOC-0/,40 items in India/KOOC-0/98/KOOC-0/and 4 items in the Philippines/KOOC-0/.

Census information has legal effect. Its function can be summarized as the following three aspects: (1) formulating policies, allocating election places and drawing up construction plans. For example, the US Constitution stipulates that a census should be conducted every 10 years, so as to accurately allocate seats in the House of Representatives, and determine the number of state legislators and the federal government's funds for each state according to the population ratio. (2) It is used to study the regional distribution, fertility, death, growth, gender, age, urban and rural areas, occupation, culture and other characteristics of the population. (3) Decide on the supply of housing equipment, food, clothing, entertainment facilities, medicines, the layout of commercial outlets, the distribution of goods and labor, etc. Population size, distribution, age and gender information obtained through the census.

Census information is only a small part of the huge information family of digital earth. Digital Earth can integrate census information with other geospatial data. For example, population information is filed and managed by departments and administrative units, and it echoes the spatial characteristics of ground objects (such as ground object images) through the Internet. Through the digital earth, people can browse a series of electronic maps (such as topography, water system, land use, population distribution, etc. ) and the description of a country or region on the earth, to obtain detailed information about the population and its living space, including the total population, the ratio of male to female, education level, nationality, occupation, economy, education, commerce, health care, public welfare, employment, social insurance, etc. You can get detailed information, including photos, by visiting your home page.

Census information is widely used in population analysis and prediction. By interpreting high-resolution satellite images, scientists can obtain information about urban buildings and estimate the population of residential areas. The digital earth supported by satellite remote sensing, geographic information system and internet technology has strong analysis, evaluation and simulation capabilities. For example, scientists in pendleton, California, USA can simulate the effects of different population growth on biodiversity by collecting information such as topography, soil types, annual rainfall, vegetation, land use and land ownership. For another example, through the census data, we can simulate the dynamic growth, population distribution and migration of urban population. The immigration problem in large-scale projects such as the Three Gorges Project can be solved with the help of the network function, interoperability and geographic information system technology of the digital earth.