Blue ice occurs when snow falls on a glacier, is compressed, and becomes part of a glacier

Glacier

A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...

 that winds its way toward a body of water (river, lake, ocean, etc.). During its travels, air bubbles that are trapped in the ice are squeezed out, and the size of the ice crystals increases, making it clear. A good example of blue ice was observed in Tasman Glacier

Tasman Glacier

The Tasman Glacier is the largest of several glaciers which flow south and east towards the Mackenzie Basin from the Southern Alps in New Zealand's South Island. It is New Zealand's longest glacier.-Geography:...

, New Zealand

New Zealand

New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

 in January 2011.

In some areas, earthquakes have raised the blue ice above the ground and created formations much like large frozen waves.

The blue color is often wrongly attributed to Rayleigh scattering

Rayleigh scattering

Rayleigh scattering, named after the British physicist Lord Rayleigh, is the elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the light. The particles may be individual atoms or molecules. It can occur when light travels through...

. Rather, ice is blue for the same reason water is blue: it is a result of an overtone

Overtone

An overtone is any frequency higher than the fundamental frequency of a sound. The fundamental and the overtones together are called partials. Harmonics are partials whose frequencies are whole number multiples of the fundamental These overlapping terms are variously used when discussing the...

 of an oxygen-hydrogen (O-H) bond stretch in water which absorbs light at the red end of the visible spectrum.

Antarctic runways

Blue ice is exposed in areas of the Antarctic

Antarctic

The Antarctic is the region around the Earth's South Pole, opposite the Arctic region around the North Pole. The Antarctic comprises the continent of Antarctica and the ice shelves, waters and island territories in the Southern Ocean situated south of the Antarctic Convergence...

 where there is no net addition or subtraction of snow

Snow

Snow is a form of precipitation within the Earth's atmosphere in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. Since snow is composed of small ice particles, it is a granular material. It has an open and therefore soft structure, unless packed by...

. That is, any snow that falls in that area is counteracted by sublimation

Sublimation (physics)

Sublimation is the process of transition of a substance from the solid phase to the gas phase without passing through an intermediate liquid phase...

 or other losses. These areas have been used as runway

Runway

According to ICAO a runway is a "defined rectangular area on a land aerodrome prepared for the landing and take-off of aircraft." Runways may be a man-made surface or a natural surface .- Orientation and dimensions :Runways are named by a number between 01 and 36, which is generally one tenth...

s due to their hard ice surface which is suitable for aircraft

Aircraft

An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

 fitted with wheels rather than skis.