The higher you rise in the mountains, the colder it becomes. This truth is being studied at school. And if you climb in the mountains very high, you can see the snow that lies there all year round.
In this article we will talk about what a snow line is. And also about what it is caused by and what its height depends on.
What is a snow line? Definition of the term
With the rise for every 100 meters, the air temperature decreases by 0.6 degrees. And the amount of precipitation, respectively, is increasing. At high altitudes, they fall in the form of snow. In nature, there is a certain level above which the snow does not melt at all in the mountains. It is he who is usually called the snow line (or border).
This is a very simplified interpretation of the term. What is a snow line from a more scientific point of view? So, the famous scientist M.V. Lomonosov called it the “frosty layer of the atmosphere”. By the way, it was he who first established that the snow line in the mountains and its height depend primarily on the latitude of the terrain.
So, the snow line means the conditional boundary on the earth's surface, above which the accumulation of precipitation in solid form prevails over their melting. This border can be clearly seen in the photograph below:
Scientists distinguish several types of snowline:
- theoretical;
- local
- seasonal.
In addition, in glaciology there is such a thing as “level 365”. This is the minimum border within which the snow cover lies all year round and does not melt.
What determines the height of the snow line?
Why in some places of the planet snow literally lies at the foot, and in others - covers only the highest peaks with modest “caps”? In which mountains does the snowline go higher and in which lower? And why?
The answer to all these questions was found by Lomonosov. The main reason for the different heights of the snow border is the geographical latitude of the area. The table below shows the rounded values of this parameter depending on latitude.
Latitude | Snow Line Height Values for the Northern Hemisphere (in meters) | Snow Line Height Values for the Southern Hemisphere (in meters) |
0-10 | 4675 | 4720 |
10-20 | 5475 | 5780 |
20-30 | 5250 | 5300 |
30-40 | 4900 | 3200 |
40-50 | 3170 | 1700 |
50-60 | 2500 | 890 |
60-70 | 1150 | 0 |
70-80 | 790 | 0 |
80-90 | 650 | 0 |
Zeros in the last three lines (in the column of the Southern Hemisphere) should not lead the reader into bewilderment. Indeed, it is in these latitudes that the largest "refrigerator" of our planet is located - the mainland of Antarctica.
The height of the snow line also depends on other factors: climatic and orographic. For example, this parameter is affected by the average annual rainfall, and features of the relief, and the proximity of the ocean. The height of the snow line also depends on the exposure of a particular slope. For example, on the northern (shaded) slope of the ridge, it will pass much lower than on the southern (sunny) one.
What happens to snow in the mountains?
If the snow accumulates high in the mountains and does not melt, then where does it go? If we say that there is much more snow falling above the snow border than it can melt, then over the course of many millennia there would have accumulated a myriad of solid precipitation! However, this does not happen. Why?
The fact is that the snow, one way or another, falls down. Either under the influence of gravity, or under the influence of the work of the wind. So, light snow grains are driven by the wind down the slope, where they slightly thaw under the influence of sunlight and turn into the so-called firn. Further, this snowy mass continues to move down, changing its structure. Gradually, the firn turns into continuous and relatively smooth glacier ice. So the mountain glacier is born.
It is important to note that not all mountains contribute to the development of glacial masses. The topography of the territory is also important here. For the formation of a full-fledged mountain glacier, the presence on the mountain slopes of wide and deep basins, in which firn could accumulate, is necessary.
Finally…
What is a snow line? In simple words, this is the border above which snow lies year-round. The height of the snow line in different regions of the Earth is not the same. So, at the South Pole it is equal to the level of the ocean, and at the Tibetan plateau it rises to almost seven kilometers. In general, there is a strict pattern: the closer to the poles of the Earth, the lower the snow border.