Ice is solid water, and it has some amazing properties. When water freezes it expands by about 9 percent and that can have a dramatic effect on the landscape. It can shatter rocks, especially in places where the daytime temperature is above freezing but at night drops below zero such as in mountains.
Ice is also eight percent less dense than water, so it floats. Fortunately, this is the case. If ice did not float, natural bodies of water, such as lakes, would freeze from the bottom up, so when ice is formed, nothing would be able to live there.
About two percent of all the world’s water is frozen as glaciers, ice caps and permanent snow. A glacier is basically a river of ice that moves very slowly downhill under its own weight. The debris carried by a glacier scours the underlying bedrock like sandpaper, and so, on their way down to the sea or a lake, glaciers tend to follow the paths of V-shaped river valleys.
Glaciers can be quite long. The Margerie Glacier on the Alaska-Canada border has a length of 34 km. Argentina’s Perito Morreno glacier has a similar length but with a much bigger source. It is fed by the Southern Patagonian Ice Field in the Andes Mountains, the third largest reserve of freshwater on the planet.
Ice sheets feed glaciers on the Antarctic mainland and the Arctic island of Greenland. Antarctica has the bigger ice sheet. If it all melted, the global sea level would be raised by 58m! Greenland’s ice is dotted with sparkling blue pools and striking acquamarine streams. They look like jewels, but their beauty hides a darker secret – they show that the island’s glaciers are melting at an alarming rate, about six times faster than normal.
Icebergs are like ice hills and they can reach impressive size. Large icebergs can have all manner of shapes: steep sides with a flat top, or non-tabular with domes and pinnacles. Their colors can vary – white, green, blue and even black. Ice is transparent, but it absorbs most colors of sunlight except blue, so it appears blue. Green can come from algae attached to the ice, and black is the result of it having no bubbles. As most icebergs calve from glaciers or ice sheets, they are made of frozen freshwater. When they melt, they add to the volume of the sea and raise the sea level, unlike sea ice, which is frozen seawater.
Ice reflects sunlight back into space. When the ice melts, it exposes more of the dark parts of the Earth’s surface, those bits of bedrock that it inherits from a parent glacier. Exposed, they absorb more heat, and melt even faster, raising sea levels and sometimes, generating tsunamis. So ice, like water, is not only an agent of erosion and deposition. It is also a vital agent shaping the climate and health of the planet.