About the ice age

About 654.38 billion years ago, 32% of the world's continents were covered by glaciers. People call this era the Ice Age (also known as the Ice Age).

During the Quaternary period of nearly one million years, there were several glacial periods, during which there was a warmer interglacial period. The alternation of glacial periods and interglacial periods caused the expansion and retreat of glaciers on the earth, which had a great impact on the whole geographical environment, especially the biological world.

Generally speaking, the ice age mainly refers to the age of Quaternary glaciers. Because it is closest to us, it has left many traces on landforms and sediments, which makes us know more about it. In fact, in the whole history of the earth's development, there have been several such ice ages, and sometimes the scope of glaciers has expanded to North Africa, India and Australia near the equator. According to the development point of view, there may be a big glacier coming on the earth in the future.

The last ice age ended 654.38 million years ago. During that ice age, glaciers extended from the poles to the equator. In latitudes like new york, the ice layer is 654.38+0 km thick. It was a very cold time, and our ancestors witnessed it.

However, in the distant past, before the earliest ancestors of chordates appeared, there was a longer, colder and more spectacular Great Ice Age, when the whole earth was frozen into a huge snowball.

The name of this earliest ice age is the Varanga Glacier in Langille, and Joseph Kirshvink gave it an image name-1992 Snowball Earth. This history was discovered by W Brian Harlan, a geologist in Cambridge in the 1960s. When he studied rocks 700 million years ago, he found that they all had contact with ice. Some of them have scratches from glaciers, while others fall from the bottom of icebergs to the bottom of the sea. These rocks come from all over the world, including those very close to the equator. This is strange because it is hard to imagine that ice will appear in the equatorial sea level area. Although he quickly concluded through research that there was a large-scale glacier movement 750 million years ago to 580 million years ago, according to past experience, glaciers of other generations never spread all over the continents, and it was difficult to find ice even in the continents near the equator during the worst ice age.

The ice age is also called the ice age (the fourth generation of Cenozoic era), the ice age and the ice age. At present, the glacier area on the earth is 654.38+049.7 thousand square kilometers, accounting for 654.38+00% of the land area. However, in the history of the earth, the area of glaciers was many times larger, forming an ice age. The recorded Great Ice Age occurred three times with a period of nearly 300 million years. The first time happened at the end of Proterozoic about 600 million years ago, which was called the Sinian Great Ice Age. The time of the Great Ice Age was slightly different in the continents of the world, when the animals and plants on the earth were still very poor. The second time occurred from Carboniferous to Permian about 300 million years ago. The Great Ice Age mainly occurred in Gondwana, in which South America and Africa occurred and subsided earlier, and India and Australia later. After the glacier retreated, a large area of fern flora appeared. The third Great Ice Age is the most famous Quaternary Great Ice Age, and it also has the greatest influence on the present. Photo Hairy rhinoceros is a representative species of the Quaternary Great Ice Age.

[Edit this paragraph] Ice Age

A geological period with strong glaciation. Also known as the ice age. There are broad glacial periods and narrow glacial periods. The broad glacial period is also called the Great Glacial Period, and the narrow glacial period refers to an glacial period lower than the Great Glacial Period. The Great Ice Age refers to the geological period when the climate on the earth was cold, the polar ice sheets were thickened and widely distributed, and there was sometimes strong glaciation in the middle and low latitudes. During the Great Ice Age, the colder climate was called the Ice Age and the warmer climate was called the Interglacial Age. Great Ice Age, Ice Age and Interglacial Age are all geological time units divided according to climate. The duration of the Great Ice Age is equal to or greater than the epoch of geological age units, and the time interval between two Great Ice Ages can be several eras. According to statistics, some people think that the emergence of the Great Ice Age had a cycle of 654.38+0.5 billion years. The duration of glacial and interglacial periods is equivalent to the duration of geological chronological units.

In the geological history of billions of years, there have been at least three major ice ages in the world, including the late Precambrian ice age, the Carboniferous-Permian ice age and the Quaternary ice age. In areas where glaciers were once active, moraines left behind are the main objects of glacier research. The moraine layer of Quaternary Ice Age is the most complete, widely distributed and studied in detail. According to the change of glacier coverage, Quaternary can be divided into several glacial periods and interglacial periods, and the ice sheet area accounts for about 30% and 10% of the land surface area respectively. However, during the ice age, the degree of glacier development in different continents was very different. For example, the ice sheet in Europe once reached 48 north latitude, while in Asia it only reached 60 north latitude. Due to the differences of climate change and different research methods in different regions, the division of ice age is different in different places. During 1909, Germans A. Punk and E. bruckner studied the Quaternary glacial deposits in Alps, and divided and named four glacial periods and three interglacial periods. Subsequently, the world was divided into corresponding glacial periods and interglacial periods. [Edit this paragraph] Quaternary Great Ice Age

During the Quaternary Great Ice Age, glaciers expanded and subsided several times, which were called glacial period and interglacial period respectively. It is generally believed that the earth is in the interglacial period, the Quaternary Great Ice Age is shorter than the previous two, and the present climate is colder than many periods in history, so the Quaternary Great Ice Age should not end. The Quaternary Great Ice Age was not limited to the Quaternary, but began as early as the Tertiary. The times and times of ice ages and interglacial periods are not exactly the same all over the world, and the specific time of each ice age is also controversial. Glaciers in Antarctica occurred much earlier than in the northern hemisphere, and the great ice sheet was formed in the Miocene more than 20 million years ago. The international division of the ice age is based on the Alps. The ice age in the Alps was once divided into four ice ages: Yumu Ice Age, Reese Ice Age, Minde Ice Age and Gongzi Ice Age. Later, the older Danube Ice Age and Bibei Ice Age were discovered, and the latest Yumu Ice Age was studied in the most detail. The last ice age ended about ten thousand years ago. At the peak of the Quaternary Great Ice Age, the glacier area was 4710.4 million square kilometers, accounting for 32% of the land area. All of Canada and northern Europe are covered with ice sheets. After the glaciers receded, large-scale lakes were left behind, so Canada and Finland became "countries with thousands of lakes". The Quaternary Great Ice Age greatly changed the face of the earth, but it did not cause mass extinction, and species could retreat to a few "shelters" to survive. East Asia and the eastern United States are both "refuges", which have preserved many ancient species, while the Alps in Europe hinder the southward migration of species, so there are far fewer biological species in Europe than in China. At the end of Quaternary, many large mammals disappeared from the earth. Now many scholars believe that their extinction is not the result of the ice age, but may be caused by human activities.

There are different opinions about the causes of the Great Ice Age, but many researchers think it may be related to the solar system's operating cycle in the Milky Way. Some people think that the time when the sun moves near the galactic center is the smallest, which makes the planets cool and forms the Great Ice Age on the earth. Some people think that the material distribution in the Milky Way is uneven, and when the sun passes through the area with high density of interstellar material, it reduces the radiation energy of the sun and forms the Great Ice Age on the earth.

"Glaciers are products of climate" is a popular saying in glaciology. So, what is the product of climate? The author's statement is that "climate change is the reflection of changes in the earth system in the atmosphere". The cryosphere is a part of the earth system, so we can say that "part of the climate is the product of glaciers". Of course, the main part of climate should be the product of geosphere (including crust, mantle and core), because geosphere accounts for 99.9% of the total mass of the earth system. Glaciers are closely related to climate and are also restricted by the change of geosphere. We can even say that "glaciers and climate are the products of changes in the geosphere". The change of geosphere is restricted by cosmic factors. After long-term research, the author puts forward the following views: the electromagnetic coupling between the cosmic magnetic field and the core magnetic fluid may be the fundamental reason for the change of the earth's surface system, as well as the fundamental reason for the change of glaciers and climate.

1, geomagnetic coupling between the Great Ice Age and silver

In the 4.6 billion-year history of the earth, it is generally believed that there have been seven major ice ages, and many scholars have put forward many hypotheses about their causes, but they are not convincing. Recently, the author suggested that when the magnetic poles of the spiral arms of the Milky Way are in the same direction as the magnetic poles of the Earth, and the interaction time is longer than 40Ma, the Great Ice Age will occur.

The geomagnetic polarity reversal has a long period of 300 million years. The length of a galactic year is gradually shortened from 400 million years 2 billion years ago, and the length of the last galactic year is only about 200 million years. Now the solar system is passing through a spiral arm of the Milky Way, and its magnetic pole direction is positive (the same as the modern geomagnetic pole). Mark the time when the two spiral arms of the Milky Way (with opposite magnetic poles) pass through the Earth and the time when the geomagnetic field reverses on the map 1. It can be seen that when the spiral arms of the Milky Way are in the same direction as the geomagnetic polarity, and the same symbol time is maintained above 40Ma. * * * has appeared eight times in the past four billion years (table 1). Among them, the last seven times just correspond to seven major ice ages.

Table 1 comparison of the occurrence time of silver-earth (magnetic) coupling type C and the Great Ice Age (unit: 100 million years)

Before 465438+0.2 39.7 38.2 36.7 35.2 33.7 32.2 30.7 29.7 26.2 24.7 23.221.7 20.2100 mA

20.218.717.215.712.71.29.7 8.26.7 5.23.7 2.20/kloc-0.

As we all know, the Great Ice Age was always accompanied by orogeny, which was inevitable. Because when the terrain is flat, the efficiency of the atmospheric heat engine is very low, which makes the planetary wind system very weak, and the temperature difference between the polar and equatorial regions is very small, which will not form a major ice age; Only when the local topography becomes uneven due to orogeny, the efficiency of atmospheric heat engine will be greatly improved, the planetary wind system will be greatly enhanced, and the polar regions will be greatly cooled, thus forming the Great Ice Age. The Quaternary Great Ice Age was closely related to the uplift of the Qinghai-Tibet Plateau. The tectonic lifting force of orogeny comes from the transformation of the core circulation into a strong convection type, and the galactic spiral arm is in the same direction with the magnetic pole and the interaction time is more than 40Ma, which is the necessary condition for the core circulation to be excited into a strong convection type.

The uplift of the Qinghai-Tibet Plateau and the formation of the Quaternary Great Ice Age are typical examples to illustrate the above viewpoint. At 44.57MaBP, the earth's magnetic pole began to turn positive and began to interact with the positive spiral arm of the Milky Way, which made the core circulation change from earth-like to strong convection and the Qinghai-Tibet Plateau began to rise. With the geomagnetic polarity reversal as the negative pole, the plateau uplift stopped and became a leveling movement. In this way, the Qinghai-Tibet Plateau rose to a height of about 2,000 m at a rate of 2.5MaBP for many times in 45Ma, and the plateau monsoon changed greatly, and the Quaternary Great Ice Age began to appear.

2. Ice age and geomagnetic intensity change

The period of glacial and interglacial periods is 105a, which is three orders of magnitude shorter than that of the Great Ice Age. Generally speaking, it is the result of Michaelis cycle, but there are many problems that Michaelis theory can't explain. For example, the Qinghai-Tibet Plateau has been recognized as having three glacial periods in recent 730,000 years, namely, the last glacial period (1~ 70,000 years ago) and the penultimate glacial period (65,433). In fact, the combination of the three elements of the earth's orbit can change the solar radiation in polar regions by 20% ~ 30%, while the change in mid-latitude regions is less than 5%. Therefore, the author thinks that the cause of the ice age on the Qinghai-Tibet Plateau should be discussed separately. The change of geomagnetic field may be a more reasonable explanation. The "three major ice ages" is an inevitable "maximum ice age" when the frozen height of the Qinghai-Tibet Plateau rises. According to the magnetic susceptibility curve of Xifeng given by Kukla( 1987),1~ 70,000 years ago and 2.2 ~ 350,000 years ago were two periods with low magnetic susceptibility, which basically coincided with the last ice age and the penultimate ice age. However, 80 ~130,000 years and 4.8 ~ 550,000 years are the periods of high magnetic susceptibility, which basically coincide with the interglacial period. According to the results of Zoige section given by Wang Sumin et al. (1996), there were four polar drifts between 2000 and 50000, five polar drifts between 16 and 260000, and between 50000 and 160000. When polar drift events rarely occur, it corresponds to interglacial period. This also shows that the ice age is easy to occur when the geomagnetic field is weak, and the interglacial age is easy to occur when the geomagnetic field is strong. This conclusion seems to contradict the conclusion in the last section, but it is not. The direct cause of the Great Ice Age was topographic uplift, which required strong magnetic field and long-term interaction. For the ice age, even the Little Ice Age and glacier fluctuation, the altitude of the terrain is no longer the main contradiction because of the short time scale. It needs less geothermal release, which is conducive to cooling, and it is easier to meet this condition when the geomagnetic field is weak.

3. The Little Ice Age and the change of solar magnetic field.

In the 15, 17 and 19 centuries, there were three obvious ice invasions in Eurasia, which were called "Little Ice Age" by glaciologists, and the time scale was 102a, which was three orders of magnitude shorter than the ice age. These three ice age transgressions basically correspond to three sunspot minima (19th century minima), among which maunder minimum in17th century is the period with the fewest sunspots for more than 2,000 years. Less sunspots means that the solar magnetic field is weak, and its coupling with the geomagnetic field will also be weakened, leading to the advance of the ice age. The Little Ice Age is a famous disaster period in the history of the earth (the so-called "frequent disaster period in Ming and Qing Dynasties"), and another "frequent disaster period in Han Dynasty" also appeared in the sunspot minimum period. The demons of earthquake and drought have been ravaging the land of China. According to the ice core records, the "Little Ice Age" in the alpine glacier area was a period of low temperature and a little more precipitation, which was different from the low temperature and drought period in the plain area outside the mountain. This difference seems to be the result of the adjustment of topographic thermal circulation in the atmosphere.

4. Glacier fluctuations and climate change

Glacier fluctuation generally includes the advance and retreat of glacier tongue (its characteristic time is 10 1a), glacier material balance, zero equilibrium line height change (its characteristic time is 100a) and so on, which is closely related to short-term climate change. In recent 40 years, there are many kinds of geoscience data, which can be discussed in detail. Some climatologists believe that there were two abrupt climate changes during this period, one in the mid-1960s and the other in the early 1980s. In other words, the climate of more than 40 years can be divided into three periods. Hereinafter, the mid-1960s to the end of 1970s will be referred to as the 1970s, and the glacier and climate fluctuations in this period and their possible causes will be emphatically discussed.

The 1970s was a period of low temperature in the northern hemisphere (high temperature in the southern hemisphere) and low temperature and little rain in most parts of China, and the snow area on the Qinghai-Tibet Plateau also became smaller. However, due to the adjustment of topographic thermal circulation, the precipitation in high altitude areas increased slightly during this period, so the proportion of advancing glaciers increased greatly. This is quite similar to the situation in the "Little Ice Age".

The 1970s was a period of slow earth rotation, relatively few sunspots and frequent earthquakes in Chinese mainland. These characteristics are similar to the "Little Ice Age". Are there the same geophysical processes between them? This is a problem worthy of study by earth scientists.

5. Possible mechanisms of glaciers and climate change.

There is not only gravitational interaction between the earth and the universe, but also thermal and magnetic interaction. As we all know, "heat" first acts on the earth's surface. "Magnetic force" should act on the outer core of the earth first, because the outer core is magnetic fluid. When the magnetic field of the solar system (or the Milky Way) is in the same direction as the earth's magnetic field, if the magnetic field is strengthened, the convection activity in the core fluid will be enhanced; On the contrary, it will weaken the convection activity at the core. There should be various ways in which the core circulation affects the mantle convection through the core-mantle boundary, and the coupling between the core convection under the Pacific Ocean and the whole mantle convection should be one of them. There are indications that mantle convection in the Pacific Ocean may be one of the strongest in the world.

When the solar system's magnetic field weakens (such as the decrease of sunspots), the convection in the earth's core weakens due to electromagnetic interaction, so the heat uploaded from the earth's core decreases, which may be the basic reason for the temperature drop in the Little Ice Age and 1970s. On the other hand, due to the weakening of convection in the core, the "abnormal" circulation in the lower core of the Pacific Ocean becomes a sinking current, which drives the boundary layer of the core and mantle to move westward through viscosity, which is the reason why the earth's rotation slows down and the seismic activity in the western Pacific Ocean and East Asia continent increases. At this time, the mantle of East Asia continent is "abnormal" sinking, which is the basic reason for the decrease of temperature and ground temperature and precipitation in Asia and Europe. At this time, a large-scale "abnormal" downward airflow appeared over the mainland, which reduced the cloud cover and was beneficial to the enhancement of topographic thermal circulation, resulting in no decrease or even a slight increase in precipitation at high altitude, leading to the forward movement of glacier activity. This is the author's explanation of the relative progress of glaciers in the "Little Ice Age" and the 1970s. Whether this idea is correct or not needs to be tested by practice. One thing is certain, the actual situation is far more complicated than the above assumptions. The cosmic magnetic field will not only affect the core flow field under the Pacific Ocean, but also affect the core three-circle circulation and the core flow field across the equator on a global scale, making the earth's surface layer show complex changes.

Galactic year and galactic winter in the solar system-the great ice age of the earth.

The primitive solar system was born about 5 billion years ago. If the closest point to the center of the Milky Way is the beginning of the new galactic year, then the sun has passed thirteen new galactic years, and our earth has passed twelve new galactic years, with a nominal age of 13 galactic years. The stage before the New Galactic Year may be the coldest stage on the earth, and it is also the coldest stage in the galactic winter (the Great Ice Age of the Earth). The solar system is about to usher in the new year, and the time is about 8 million 4 million years later. Compared with the long galactic year, it is probably "65438+February 20th".

In the past billion years, the galactic year of the solar system has become very short. According to the flight speed of the solar system, some researchers have concluded that it takes about 250 million years for the solar system to circle the Milky Way, which is not inconsistent with Steiner's one-year interval for each Milky Way. Near the galactic center is the galactic winter of the earth, which is expected to solve the occurrence of the ancient Great Ice Age.

The solar system is flying faster and faster, and the cycle around the Milky Way is getting shorter and shorter. It may not take more than a dozen galactic years for the solar system to stop in the spiral arms of the Milky Way and run closer to the center of the Milky Way. At that time, the sun will run faster, and the rotation speed of the earth will be slower than that of Venus and Mercury now, maybe only a few days or ten days a year.

At present, the solar system runs near the galactic center, and it takes about 8 million to 4 million years to reach the nearest place to the galactic center. According to the fact that the last Great Ice Age ended from 5 million to 6,543.8+million years after the center of the Milky Way, the Quaternary Great Ice Age (more appropriately called the Cenozoic Great Ice Age) was calculated from its scale of 6,543.8+0.6 million years ago. It is speculated that the Great Ice Age lasted at least1.500-25 million years, the main ice age lasted over 30-40 million years, the Carboniferous-Permian ice age lasted about 80 million years, and the Sinian ice age lasted about 60 million years. Some people say that the Quaternary Great Ice Age is about to pass and the fifth Great Ice Age is coming, which is simply nonsense. It is also alarmist to say that global glaciers and polar ice sheets will melt due to human greenhouse gas emissions. How can human forearm resist torsion with nature's iron thigh?