Why does the snow on some high mountains not melt all the year round?

Simply put, the air pressure is low, the melting point has changed, and the ambient temperature is low.

Many peaks in the world are covered with snow all year round, like wearing a "white hat", which will not disappear even in hot summer. Even in some tropical mountainous areas, such as Kilimanjaro in Africa, Himalayas in Asia and so on. Why is this? Because the weather in mountainous areas is much colder than that in plains in the same area.

So, why is it so cold on the mountain? Because the higher the mountain, the thinner the air, and the easier it is to lose heat from the sun. Every time 100 meter rises, the temperature will drop by about 0.6℃, so at a certain height, the temperature will drop below 0℃, and the ice and snow will not melt all year round. The dividing line of this height is called the snow line. The closer you get to the poles, the lower the snow line is, because the weather there is already very cold; The closer to the equator, the higher the position of the snow line.

Also, after the top of the mountain is covered with snow and ice, 50% ~ 90% of the sunlight irradiated here is generally reflected due to the strong reflection of sunlight on the snow and ice surface, which makes the temperature here low and the snow and ice are not easy to melt.

So at the top of the mountain above the snow line, there will be snow all year round. Of course, it will snow here, and there must be a place to pile up snowflakes on the top of the mountain. Therefore, not all mountains can accumulate ice and snow. The snow and ice on those snow peaks are not absolutely constant all year round. If there is strong sunlight, some will melt. But soon after, it was supplemented by snowfall, so the snow and ice can always exist, forming a glacier to move down.

"Rome was not built in a day." Those "white hats" on the top of the mountain were not formed overnight, but gradually changed from snowflakes.