Glaciers are large sheets of ice that form when snow accumulates over the course of multiple years without fully melting. Glaciers can be quite large. In fact, some glaciers span hundreds of miles in diameter. They also can be more than a mile thick. Glaciers aren't stationary, but they move at an extremely slow pace. This is where the term "moving at a glacial pace" comes from.
Older snow in glaciers remains buried beneath thick layers of new snow. The immense weight of the upper layers of snow compresses the lower layers of snow and ice. This turns the older snow into a unique type of ice, called blue ice. The ice is blue because air bubbles are squeezed out of the ice. As snow continues to pile on the glacier, the layer of blue ice becomes thicker and thicker over the course of many years.
The blue ice that glaciers are made of is exceptionally dense. This is one reason why glaciers cannot melt quickly even if temperatures temporarily rise well above freezing.
Once glaciers have formed, they influence the climate of the area. The area that is covered tends to be significantly colder than the surrounding area. This is because the ice reflects sunlight. In some areas covered by glaciers, the temperature never rises above freezing.
Where are they found?
The climate has to be incredibly cold for glaciers to form. This type of climate is common in the highest reaches of mountain ranges, particularly in mountainous areas near the poles. However, these conditions can also occur in relatively low lying areas that are close to the poles.
The two largest glaciers in the world are the Antarctic ice sheet and Greenland. Both of these glaciers are located near the poles. There also are extremely large ice sheets in the Himalayas, on mountain ranges in Alaska, and in the Alps.
Currently, they cover approximately 10% of the world. However, they used to cover a much larger portion of the Earth. In fact, glaciers covered around 30% of the Earth during the last ice age, which ended around 12,500 years ago. During that time, a massive ice sheet covered much of the northern part of North America, large tracts of Europe, and Asia. The world's mountain ice sheets were also much larger than they are now, and there were large ice sheets on mountain ranges as far south as central Mexico and the northern portion of South America. The glaciers of the Himalayan Mountains were also far larger than they are today. The Antarctic ice sheet was also much larger than it is now. It extended as far north as the southern part of South America.
Glaciers aren't just found on Earth. There are other parts of the solar system that have glaciers. The polar ice sheets on Mars are some of the most notable examples of this. These ice sheets have some similarities to polar ice sheets on Earth.
Geological features formed by Glaciers
Glaciers erode the land underneath them due to their movement and immense weight. There are many features on Earth that have been carved out by glaciers, including lakes and moraines. Some valleys in mountain regions have been carved out by the movement of glaciers. In addition, large amounts of dirt and rock are piled up in front of the moving glacier. If or when they melt, these piles are left behind, and these deposits can be seen in various regions of the United States.