permafrost, a special soil that is below zero degrees Celsius and contains ice, is distributed in high latitudes and high altitude areas around the world, such as the small and small Xing'anling in my country, the Qinghai-Tibet Plateau and other places.
Frozen soil has extremely special properties, so it can form a variety of peculiar frozen landforms. The "black magic" mentioned in this article is caused by the permafrost.
01
Groundwater is about to emerge
An important condition for forming frozen soil is that the soil contains water. When this water continues to freeze and melt, many interesting landforms will be formed.
Underground ice , as the name suggests, is ice formed in permafrost. has ice condensation, buried ice, vein-like ice, etc. . Underground ice is an extremely important water resource in permafrost areas. The existence of underground ice has a great impact on permafrost engineering and climate change.
Underground ice. Image source: Wikipedia
Frozen swelling refers to the landform in which the soil is swelling upward due to the increase of ice under frozen conditions. Specifically, the melting layer freezes from top to bottom and from bottom to top in winter, the cross-water section shrinks, and the water on the frozen layer is under pressure. At the same time, the water migrates during the freezing process, which will produce an ice-cold layer. As the freezing surface develops downward, when the pressure of water on the frozen layer is greater than the strength of the overlying soil layer, a bulge occurs on the surface, forming a frozen hill.
Frozen and swollen hills are a frozen landform that can be seen frequently in permafrost areas in my country. The diameter of the bottom of the frozen swelling mound ranges from a few meters to dozens of meters, with a height of 1 to 2 meters, and some can reach 3 to 5 meters. There are often crisscrossing cracks on the surface of frozen mounds. The largest known frozen hill in my country is on the Qinghai-Tibet Highway 62 road. Its bottom diameter is 40~50 meters and up to 20 meters .
frozen mound profile. Image source: Wikipedia
In permafrost areas, sometimes you can see silver-shining ice bodies from a distance, which is the ice cone. The melting layer in winter freezes, the groundwater pressure increases, breaks through the overlying soil layer and overflows over the surface, the overflow ice body gradually increases and rises, and becomes a conical . The overflow water flows and freezes while flowing and extends along the original groundwater flow path, thus forming an ice cone.
The shape and size of the ice cone vary greatly. Some have a diameter of 2 to 3 meters, some extend on the ice slope for dozens or even hundreds of meters, and sometimes with several overflow outlets. Ice is very common in frozen soil areas.
melted ice cone. Image source: China Science Expo
02
Frozen soil also likes circles
Have you seen circles of gravel? The unique freeze-thaw sorting effect of frozen soil will separate different substances, so this "circle circle" phenomenon is more likely to occur in frozen soil areas. stone ring and frozen grass ring are typical "circle circle" landforms .
is on the gentle and thick surface layer. After the freeze-thaw separation of , the soil and small rock chips are concentrated in the middle, and the rock blocks will be squeezed out to the surrounding area, becoming polygonal or nearly circular, as if someone consciously turns the stone into a circle. This frozen landform is called stone rings.
stone ring. Image source: Wikipedia
The area where the stone ring forms must be mixed with the thickness of the rocks and soil, and also require sufficient moisture. The duration of the temperature fluctuates around zero degrees Celsius is longer . Only in this way can the stones mixed in the soil be squeezed out.
Stone rings are commonly found on flat land not far from the river beach or river exit passes because they have the conditions for the formation of stone rings.
Frozen grass ring forms a polygonal or approximately circular shape of the turf on the ground surface, and is exposed in between. This is a relatively rare ice margin landform in the frozen soil area, with red and yellow in the middle, green in the surrounding area, dazzling.At present, scientists are not very clear about its formation mechanism and process.
freezing grass ring. Image source: References [1]
03
"gravel stone" in frozen soil
Due to the presence of cracks, when the water freezes and expands, the rock breaks into many small pieces, or due to temperature changes, the minerals that make up the rock expand and contract unevenly, causing the rock to burst . In this case, a large number of angular rock blocks and rock cuts of varying sizes will be generated. Under the condition of gentle terrain, most of the rock cuts remain in place, forming gravel covering the ground. This is Shihai .
Shihai. Image source: Wikipedia
Stone sea is distributed in my country's Qinghai-Tibet Plateau, western alpine mountains and the northern permafrost areas of the Greater Xing'anling . The development of a stone sea not only requires the rock to be brittle and has many cracks, but also requires certain hydrothermal conditions. That is, the rocks must have a certain amount of moisture, and the temperature of the moisture must change greatly, and the temperature must fluctuate for a long time around 0℃. The material source and production of
shiliupo is roughly similar to that of Shihai, but the two appear different geomorphological parts. The sea of stone is more common in gentle mountain corners, while the slope of stone flows appears on the slope.
In addition to being produced by cold weathering on the slope, rock blocks and debris on the rock flow slope also roll down from the mountain under the action of gravity. This determines that the composition of stone flow slope is thin at the top and thick at the bottom. There are mostly small rock chips above the slope, and there are mainly large rock blocks under the slope.
Stone flow slope. Image source: Wikipedia
Stone flow slope is a common ice-edge geomorphology in permafrost areas. It is widely distributed in the Daxinganling Mountains and the alpine and plateaus of western my country, and can be seen almost everywhere.
Under natural conditions, surface substances are often mixed in thickness. Due to the different thermal conductivity of stones and soil, the freezing speeds are also different. The gravel has a high thermal conductivity and will freeze first, and the water will migrate to the stones and form ice near them. After the water forms ice, the volume will expand, causing the gravel to move. In this way, the coarse substances and the fine substances will separate. This phenomenon scientists call it freeze-thaw sorting , because it is like a sieve, separating different substances.
Stone strips is formed by repeated freeze-thawing and freeze-thaw sorting of gravels, causing the gravel to gather in a low place, and then extend downwards slope by gravity. Therefore, stone strips often exist at the same time as the rock slope, and gravel and fine-grained substances are arranged in strips in a slope.
stone strips, "brothers" of Shiliupo. Image source: Wikipedia
Rock blocks and rock debris produced by cold weathering gather in the grooves under the slope under the action of gravity. The gravel slowly moves down the grooves, forming a small river filled with stones, so it is named Shihe .
Shihai, Shiliupo, and Shihe are brothers of the same clan. They have organic connections with each other and often appear at the same time in the same mountain. They are often paved with huge rocks on the mountain, with gravels all over the hillsides and gravels on the foothills.
Shihe. Image source: Wikipedia
Nature's "gravel stone" is formed by rocks in a special permafrost environment. Although its form is unique, only when humans carefully protect the fragile permafrost environment can it bring continuous shock to humans.
References:
[1] Hjort, Jan. (2006). Environmental Factors Affecting the Occurrence of Periglacial Landforms in Finnish Lapland: A Numerical Approach.
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