stalagmite
During the Han and Tang dynasties, the nomads in the north did not seem to be fierce, and although the Xiongnu and Turks had conflicts with the Central Plains, they obviously did not desperately attack south. At most, it is to go south to loot, and when it is enough, it will return to the northern steppe.
At the end of the Western Jin Dynasty, the end of the Song Dynasty, and the end of the Ming Dynasty, the nomads suddenly became fierce, and the Xianbei, Jurchen, Mongol and other ethnic groups not only went south on a large scale, fighting to the death with the Han people in the Central Plains, but also captured the Han land and lived for a long time.
The well-ridden nomads were a great threat to the Han land
There is no definite answer to this question in history books, and later generations have their own accounts, but the subjectivity in the statement seems to be great.
If the stalagmites in the cave can answer this question, it seems to be a joke, but telling all the secrets of the stalagmites is not a joke, but the most objective expression, the closest answer to the truth.
Okay, let's start with stalagmites.
There are many caves around the world, the dripping water in the cave, containing calcium carbonate, magnesium hydroxide and other substances, when the water evaporates, calcium carbonate, magnesium hydroxide precipitation, continuous accumulation, the formation of stalagmites.
Under normal circumstances, the formation of a centimeter-tall stalagmite takes 10,000 years, and a thick and tall stalagmite takes hundreds of thousands of years.
In the south there is a rainy season and dry season, in the north there is spring, summer, autumn and winter, there is no rain in the dry season, and although it snows in winter, it is difficult for the water on it to drip because the soil layer in the upper part of the cave is frozen.
For this reason, stalagmites in the south grow during the rainy season and stop growing during the dry season. Stalagmites in the north grow in spring, summer and autumn and stop growing in winter.
This situation makes stalagmites form growth rings, and tree growth rings form a reason.
The lifespan of stalagmites can be calculated from the growth rings. The figure below is a cross-sectional view of a stalagmite, the large picture on the left is the growth ring seen with the eye, circle by circle, and the small picture on the right is seen under the microscope, which is more accurate and careful.
The growth rings of stalagmites
How to judge the information of tens of thousands of years ago through stalagmites?
The reason is also very simple.
The stone walls and soil above the cave contain magnesium carbonate. If the climate is dry and there is little rainfall in a given year, less water will penetrate into the cave in that year, and the number of water droplets on the roof of the cave will be greatly reduced. The stalagmite rings corresponding to this year are very thin, if there is none.
On the contrary, the rainfall is frequent and the water droplets in the cave are constant, and the annual rings corresponding to the year are relatively thick. The more water droplets, the more calcium carbonate it brings.
There is not only calcium carbonate in stalagmites, but also a small amount of magnesium, and the amount of magnesium can reflect the temperature.
Although the soil cliff contains magnesium oxide, magnesium oxide is difficult to dissolve in water, and at room temperature, only 0.02 grams of magnesium oxide can be dissolved per liter of water.
But magnesium oxide has a characteristic, the lower the water temperature, the worse his solubility, the higher the temperature of the water, its solubility will increase.
The magnesium content of a certain layer in the stalagmite rings is determined, and the magnesium content is very low, indicating that this layer represents a low temperature in the year. Conversely, if the magnesium content is high, it means that the temperature of the year is high.
In addition to magnesium, there are many trace elements, such as strontium, barium, etc., these elements also have their own characteristics, sensitive to temperature and humidity, stalagmites in a thin layer of growth rings, strontium, barium content fluctuations, reflecting the regular changes of temperature and humidity throughout the year.
Seasonal rotation of trace elements in stalagmites
In the eyes of paleometeorologists, stalagmites are a climate recorder, a very good recorder, never leaving their posts, hundreds of thousands of years or even more than a million years of climate conditions.
According to stalagmite records, people verify the legend of the ancient Great Flood, while also explaining many previous historical puzzles.
For example, during the Han and Tang dynasties in China, the nomads in the north did not seem to be very fierce, although they had conflicts with the Central Plains dynasty, but they did not pursue and fight fiercely. It turned out that according to the information provided by the paleoclimate, the entire northern hemisphere was warm and rainy during this period, the grass in the northern steppe was more sheep fat, and the Xiongnu and Turks had enough to eat and drink, and their ferocity was not so strong.
In the Southern and Northern Dynasties, the late Song Dynasty and the late Ming Dynasty, the climate in the northern hemisphere was cold, rainfall decreased significantly, and grain harvests failed. The life of the Han people in the Central Plains is not good, the life of the grassland nomads in the further north is even worse, the grass is not growing well, and a large number of cattle and sheep freeze to death in winter, and the survival of the entire ethnic group is greatly threatened.
When the sheep freeze to death, they will be fierce and evil
At this moment, they were fierce and desperately attacked the Han people in the Central Plains to the south, not only looting and killing people, but also occupying the Han land and not wanting to return to the grassland.
Full-fed tigers and wolves generally do not take the initiative to attack humans, and tigers and wolves in a hungry state are different, and the same is true of men on the steppe.