What is permafrost?
People living in the north have this experience. In winter, when the temperature drops below zero, if you dig soil outdoors, you will find that the soft soil has now become very hard. Often only a white spot is left. Careful people will find that there are some small ice crystals in this hard soil, and if you continue digging without getting discouraged, you will find that this layer of hard soil is not very thick, and there is still relatively soft soil below it. This layer of soil containing ice crystals is frozen soil.
Why does this happen?
Because the soil contains more or less water, but when the temperature drops to zero or below, the water in the soil will condense into ice and freeze the soil, thus producing frozen soil. But why do we see only one layer of frozen soil instead of all frozen? It turns out that the earth under our feet has a very special property, that is, its surface temperature decreases with increasing depth, but when it reaches a certain depth, its temperature no longer decreases, but maintains a basically constant temperature all year round. Scientists This layer is called the thermostatic layer. As it gets closer and closer to the center of the earth, the temperature gradually increases.
In this way we know that permafrost is a special soil that is below zero degrees Celsius and contains ice. Therefore, frozen soil is different from loess, black soil, and red soil. It is a kind of frozen soil. It can be frozen black soil or frozen loess. Of course, there is less frozen red soil, because red soil mostly develops in In the south, the temperature in the south rarely drops below freezing.
The frozen soil we just mentioned is just a type of frozen soil. When the weather gets warmer, this frozen soil will melt. We call this frozen soil seasonal frozen soil. In addition, in some places there is a kind of frozen soil that can last for many years, that is, permafrost. For example, in the Arctic or the Tibetan Plateau, because the temperature there is below zero all year round, the frozen soil will remain unchanged all year round. , even in warmer years, only a small layer on the surface melts.
The existence of frozen soil is mainly affected by temperature. The temperature gets lower as you go to higher latitudes. Because the Southern Hemisphere has less land area, permafrost is mainly distributed in Eurasia and the northern part of North America. At the same time, we also know that the temperature gets lower as you go higher. In some high mountains, the temperature is below zero all year round. Therefore, permafrost also exists on high mountains and plateaus in middle and low latitudes, such as the Andes Mountains in America and Africa. Mount Kilimanjaro and the Tibetan Plateau in my country.
Permafrost on the Qinghai-Tibet Plateau
Human activities are mostly concentrated in warm areas or low-altitude plains, so not much is known about permafrost, but with the expansion of human activity space As the demand for resources increases, humans have gradually turned their attention to space, oceans and cold polar regions. For example, in the past 40 to 50 years, the United States, the United Kingdom, Canada and other countries have stepped up the development of oil and natural gas in the Arctic and Arctic offshore to solve the energy crisis. However, cold areas including permafrost have their own unique environmental characteristics. It is a very fragile environmental system that cannot be restored once it is damaged.
Engels said, "We should not be overly intoxicated with our victory over nature. For every such victory, nature takes revenge on us." The development of nature must be based on understanding and obeying the laws of natural development. Only in this way can we leave a scar-free earth to people living in cold areas and future generations!
Distribution of permafrost in China
Permafrost in my country is divided into high latitude and high altitude permafrost. High-latitude permafrost is mainly concentrated in the Greater and Lesser Khingan Mountains, covering an area of 380,000-390,000 square kilometers. Permafrost at high latitudes is the permafrost on the southern edge of the Eurasian continent. Its horizontal distribution obeys the latitudinal zonal rules, that is, the area of permafrost is about 10% and the thickness is thicker toward higher altitudes.
High-altitude permafrost is distributed in the Qinghai-Tibet Plateau, Altai Mountains, Tianshan Mountains, Qilian Mountains, Hengduan Mountains, Himalayas, and certain mountainous areas in the east, such as Changbai Mountain, Huangganliang Mountain, Wutai Mountain, Taibai Mountain, etc. The formation and existence of high-altitude permafrost are controlled by local altitude.
Distribution of permafrost in the world
Now let us conduct an inspection from south to north to understand the development of permafrost. We started from Nenjiang, a city in the northern Songnen Plain of my country, and conducted observations while walking north. In the Nenjiang River we will find many areas of frozen soil, which indicates that we have reached the southern limit of permafrost. If we continue to go north to reach the northernmost end of my country's railway, we will find that the frozen soil that originally appeared in blocks has been connected into one piece, and the thickness of the frozen soil has increased to 50-120 meters. Continuing to go north and entering the Arctic Circle, we will find that the original towering ancient trees have disappeared, and what comes with it is a tundra scenery. The thickness of the frozen soil here has increased to 200-600 meters, and even reached 1,000 meters in some places. . Going north, we reach the end of the trip - the coast of the Arctic Ocean. The climate here is extremely cold and the permafrost is 400-900 meters thick. This is the place with the last thickest permafrost in the world, with the last place reaching 1,400 meters.
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