Some mountains have snow-capped peaks all year round due to the high altitude and low temperatures that prevail at these altitudes. The cold air at high altitudes condenses atmospheric moisture, leading to the formation of permanent snow and glaciers.
The local climate plays a key role in ensuring that certain mountains remain snow-covered year-round. For example, near coastal regions, the significant humidity from the oceans provides a frequent and consistent supply of snow precipitation. In contrast, a mountain located in a dry area may quickly run out of fresh snow, even with relatively cold temperatures. Some mountain ranges also benefit from particularly cool weather due to local winds, which constantly cool the peaks and promote the maintenance of a permanent snow cover.
The higher you go in altitude, the lower the temperature gets. Generally, you lose an average of 6.5 degrees Celsius for every 1,000 meters of ascent. Why? Because the atmospheric pressure decreases up there and the air is less dense: it retains heat less effectively. As a result, even in the tropics, very high peaks often keep their white caps year-round. This is why high mountains like Kilimanjaro or the Himalayas consistently display snow-capped summits, despite their geographical position sometimes being close to the equator.
The peaks that remain snow-covered all year round do not depend solely on the cold, but also on the regular supply of precipitation. Without fresh snow, there is no lasting white summit! Humid air currents, often coming from the oceans, encounter mountains and must rise: as they ascend, they cool down and release their moisture in the form of snow at high altitudes. If these flows are consistent, the mountain receives a constant supply, thus sustaining a permanent snow cover. In contrast, equally high peaks located in areas with dry currents will have much less snow, or even none at all. In the Himalayas, for example, some slopes receive much more snow than others, simply due to the prevailing direction of the moisture-laden atmospheric currents.
If a slope is south-facing (in the Northern Hemisphere), it receives more direct sunlight and heats up more, which can prevent the snow from lasting all year round. Conversely, a north-facing slope is in the shade for a good part of the day, thus maintaining a cool temperature that better protects the snow and promotes the formation of permanent glaciers. The difference in sun exposure explains why two neighboring mountains, despite being similar in size, can sometimes have very different snow cover on their slopes. Same altitude, same region, but not the same duration of sunlight: as a result, one will be white all year round, the other much less so.
Permanent glaciers are large masses of ice that never completely melt, even in summer. Thanks to their thickness, they store cold throughout the year. Fresh snow falls on top and accumulates year after year. On the surface, a small part melts in summer, but since it is very cold in the depths, the glacier remains intact. This phenomenon of limited melting and continuous refreezing allows glaciers to withstand seasonal warming and keep the peaks permanently white. Of course, these glaciers are sensitive to climate: if average temperatures rise too much and snowfall decreases, they retreat, thin out, and may eventually disappear.
Due to their high altitude, some mountain peaks serve as valuable indicators for studying climate warming, as changes in snow cover are observed rapidly there.
The Mount Everest, the highest mountain in the world, experiences temperatures that can drop below -60°C at its summit, making the permanent presence of ice and snow possible.
The snow that remains year-round on certain peaks provides an essential reserve of freshwater for the rivers and communities located nearby, especially during dry periods.
Although located in the warm and sunny regions of the world, the Andes mountains host some of the most extensive tropical glaciers, which exist solely due to their high altitude and substantial precipitation.
Among the most famous peaks are Mount Everest in the Himalayas, Mont Blanc in Europe, Kilimanjaro in Africa, and Aconcagua in the Andes. Each of these summits has glaciers and eternal snows due to their altitude and climatic characteristics.
Yes, climate change is causing average temperatures to rise, reducing snow accumulation, accelerating glacier melt, and thus raising the limit of permanent snow to higher altitudes.
This mainly stems from a lack of snowfall and significant exposure to sunlight. A dry climate or a location that is very exposed to the sun can prevent the formation and maintenance of glaciers, even at high altitudes.
With the increase in altitude, the temperature decreases on average by 6.5°C for every 1,000 meters (average temperature gradient). This explains why, beyond a certain height, known as the snow line, snow never completely melts, even in summer.
No, not necessarily. While altitude plays a major role, other factors such as local climate, precipitation, sun exposure, and atmospheric currents can influence the presence or absence of persistent snow on the peaks.
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