Sastrugi, or zastrugi are sharp irregular grooves or ridges formed on a snow surface by wind erosion

Erosion

Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...

 and deposition, and found in polar and temperate snow regions. They differ from sand dunes

Dune

In physical geography, a dune is a hill of sand built by wind. Dunes occur in different forms and sizes, formed by interaction with the wind. Most kinds of dunes are longer on the windward side where the sand is pushed up the dune and have a shorter "slip face" in the lee of the wind...

 in that the ridges are markedly parallel to the prevailing winds.

Sastrugi are various surface irregularities resulting from wind erosion, saltation of snow particles and deposition. Smaller irregularities or this type are known as ripples (small, ~10 mm high), or wind ridges.

Larger features are especially troublesome to ski

Ski

A ski is a long, flat device worn on the foot, usually attached through a boot, designed to help the wearer slide smoothly over snow. Originally intended as an aid to travel in snowy regions, they are now mainly used for recreational and sporting purposes...

ers and snowboard

Snowboard

Snowboards are boards, usually with a width the length of one's foot, with the ability to glide on snow. Snowboards are differentiated from monoskis by the stance of the user...

ers. Traveling on the irregular surface of sastrugi can be very tiring, and can risk breaking equipment—ripples and waves are often undercut, the surface is hard and unforgiving with constant minor topographic changes between ridge and trough.

Etymology

The words sastrugi/zastrugi are Russian-language plural

Plural

In linguistics, plurality or [a] plural is a concept of quantity representing a value of more-than-one. Typically applied to nouns, a plural word or marker is used to distinguish a value other than the default quantity of a noun, which is typically one...

s: the singular

Grammatical number

In linguistics, grammatical number is a grammatical category of nouns, pronouns, and adjective and verb agreement that expresses count distinctions ....

 is sastruga or zastruga. The form "Sastruga" is the German-language transliteration of the Russian word .

A Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

-type analogical singular sastrugus is used in various writings including Robert Falcon Scott

Robert Falcon Scott

Captain Robert Falcon Scott, CVO was a Royal Navy officer and explorer who led two expeditions to the Antarctic regions: the Discovery Expedition, 1901–04, and the ill-fated Terra Nova Expedition, 1910–13...

's expedition

Exploration

Exploration is the act of searching or traveling around a terrain for the purpose of discovery of resources or information. Exploration occurs in all non-sessile animal species, including humans...

's diaries, and Ernest Shackleton

Ernest Shackleton

Sir Ernest Henry Shackleton, CVO, OBE was a notable explorer from County Kildare, Ireland, who was one of the principal figures of the period known as the Heroic Age of Antarctic Exploration...

's The Heart of the Antarctic.

Formation mechanism

Under the wind, free snow particles accumulate and drift in a way similar to barchan

Barchan

A barchan dune, also barkhan is an arc-shaped sand ridge, comprising well-sorted sand. This type of dune possesses two "horns" that face downwind, with the slip face at the angle of repose of sand, or approximately 35 degrees . The upwind side is packed by the wind, and stands at about 15 degrees...

 dune

Dune

In physical geography, a dune is a hill of sand built by wind. Dunes occur in different forms and sizes, formed by interaction with the wind. Most kinds of dunes are longer on the windward side where the sand is pushed up the dune and have a shorter "slip face" in the lee of the wind...

s of sand. For this reason, the resulting drifting snow shapes are also popularly referred to as "barchans", while Inuit

Inuit

The Inuit are a group of culturally similar indigenous peoples inhabiting the Arctic regions of Canada , Denmark , Russia and the United States . Inuit means “the people” in the Inuktitut language...

 of Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 call them kalutoqaniq. When winds slacken, barchans"/kalutoqaniq consolidate via sublimation

Sublimation

Sublimation may refer to:* Sublimation , the change from solid to gas without entering liquid phase* Sublimation , the transformation of emotions* Sublimation , a music album by Canvas Solaris-See also:...

and recrystallization. Subsequent winds erode kalutoqaniq into sculptured forms of zastrugi. Inuit call large sculptirings kaioqlaq and the small ripples tumarinyiq. Further erosion may turn kaioqlaq back into a drifting kalutoqaniq. An intermediate stage of erosion is mapsuk, an overhanging shape. At the windward end of a ridge, the base erodes faster than above, producing a recognizable shape of anvil tip pointing upwind.