Why doesn't the snow on the top of the mountain melt all the year round?

Why doesn't the snow on the top of the mountain melt all the year round?

Some peaks in Qilian Mountain, Tianshan Mountain, Kunlun Mountain and Himalayan Mountain in western China are covered with snow and ice all the year round, like wearing a "white hat", which will not disappear even in summer. In the tropics, some peaks are covered with snow all year round. This is because the temperature on the mountain is very low and the weather is very cold.

Why is it so cold on the mountain? Because the higher the mountain is, the thinner the air is, and the heat from the sun is easily lost. Roughly every rise 100 meter, 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 temperature there is already relatively low; In the tropics, the position of snow line will rise.

After the top of the mountain is covered with ice and snow, the sun shines here. Due to the strong reflection of sunlight on the surface of ice and snow, it can generally reflect 50%-90% of light and heat, and most of the heat is reflected, which makes the temperature here low and the ice and snow are not easy to melt.

Therefore, those peaks whose height exceeds the snow line are covered with snow all year round. Under the strong sunlight, some will melt, and a little more in summer, but soon there will be snow falling, so that there will always be snow and ice on the top of the mountain, and the glacier can form a downward movement.