The protagonist of global warming is melting, do you really understand it?

When it comes to glaciers, perhaps the only thing that comes to mind is that they are melting. But did you know that our mother rivers, the Yangtze River and the Yellow River, originate from glaciers? The famous oasis in the Hexi Corridor is nurtured by the meltwater from the Qilian Mountains glaciers.

So, how were glaciers, which are so closely related to us, formed?

What exactly is a glacier?

A glacier is a natural ice body that exists in cold regions of the Earth for a long time and is formed by the continuous accumulation and metamorphism of snowfall over many years. It has a certain shape and moves. Glaciers are different from ordinary natural or artificial frozen ice. They can slide down along a certain terrain under the action of their own gravity.

(Photo source: veer photo gallery)

How are glaciers formed?

Glaciers are a form of water, which is formed by a series of changes in snow. To form a glacier, there must first be a certain amount of solid precipitation, including snow, fog, hail, etc. Without enough solid precipitation as "raw materials", it is like "cooking without rice", and glaciers cannot be formed at all.

Glaciers exist in extremely cold places. The South Pole and the North Pole on Earth are extremely cold all year round. In other areas, glaciers can only form on high-altitude mountains. We know that the higher you go, the lower the temperature. When the altitude exceeds a certain height, the temperature will drop below 0℃, and solid precipitation can exist all year round. Glaciologists call this altitude the snow line.

(Photo source: veer photo gallery)

For glaciers to develop on high mountains, in addition to having a certain altitude, the mountains must not be too steep. If the mountain is too steep, the falling snow will flow down the slope and cannot form snow, and there is no way to form a glacier.

As external conditions and time change, snowflakes will become spherical snow that completely loses its crystal characteristics after falling to the ground. This is called granular snow. This kind of snow is the "raw material" of glaciers.

(Photo source: veer photo gallery)

After the accumulated snow turns into granular snow, its hardness and compactness increase continuously with the passage of time. Large and small snow grains squeeze each other and fit tightly together. The gaps between them shrink and even disappear. The brightness and transparency of the snow layer gradually weaken, and some air is also trapped inside, thus forming glacier ice.

When glacier ice was first formed, it was milky white. After a long period of time, it became denser and harder, and the bubbles inside it gradually decreased, slowly turning into crystal clear, blue crystal-like old glacier ice.

Glaciers are formed when glacier ice slowly flows down the hillside under the action of gravity.

Wow, it seems like forming a glacier is a huge undertaking!

Classification of glaciers

There are two types of glaciers in the world: continental glaciers and mountain glaciers.

In Antarctica and Greenland within the Arctic Circle, glaciers develop on a continent, so they are called continental glaciers. In other areas, glaciers can only develop on high mountains, so they are called mountain glaciers.

The total area of ​​glaciers in the world is more than 15 million square kilometers, of which the continental glaciers in Antarctica and Greenland account for 14.65 million square kilometers. Therefore, the scale of mountain glaciers is very different from that of continental glaciers.

(Photo source: veer photo gallery)

On the huge continental glaciers, the boundless ice flows cover the mountains and valleys, with only a few peaks sticking out of the ice. The vast Antarctic glaciers have always been a mystery, with thick ice covering the true face of the Antarctic continent. Scientists have discovered through geophysical exploration that there are many small lakes under the Antarctic glaciers, and that there is life in these lakes.

(Photo source: veer photo gallery)

Glaciers in my country

In the west of my country, there are majestic plateaus and towering mountains, which have given birth to many mountain glaciers. my country is one of the countries with the most developed mountain glaciers in the world. There are about 2 million square kilometers of high mountains and plateaus above 4,000 meters in my country. The Qinghai-Tibet Plateau and the Pamir Plateau, known as the roof of the world, are located in the west, and the majestic Himalayas, Kunlun Mountains, Qilian Mountains, Tianshan Mountains and Altai Mountains reach the sky.

All glaciers in my country are mountain glaciers. Even during the Quaternary Ice Age, when glaciers were at their peak, the size of the glaciers increased greatly, but they did not develop into continental glaciers. Many experts previously believed that the Qinghai-Tibet Plateau was once covered by a large glacier during the Quaternary. Even now, some foreign experts still hold this view. However, after investigation and demonstration, Chinese glaciologists have basically denied this view.

(Photo source: veer photo gallery)

Conclusion

Glaciers are the largest freshwater resource on Earth and the largest natural reservoir after the ocean. Looking up at the pure and magnificent glaciers, while praising the ingenuity of creation, we can't help but sigh at the insignificance of human beings. We should always be in awe and live in harmony with nature.

Produced by: Science Popularization China

Author: Earth Story

Producer: China Science Expo