Kolsås (), sometimes called Kolsaas, is a

hill A hill is a landform that extends above the surrounding terrain. It often has a distinct Summit (topography), summit. Terminology The distinction between a hill and a mountain is unclear and largely subjective, but a hill is universally con ...

in the municipality of

Bærum Bærum () is a municipality in the Greater Oslo Region in Norway that forms an affluent suburb of Oslo on the west coast of the city. Bærum is Norway's fifth largest municipality with a population of 128,760 (2021). It is part of the electoral ...

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...

. Geologically, Kolsås belongs to the

Oslo Graben The Oslo Graben or Oslo Rift is a graben formed during a geologic rifting event in Permian time, the last phase of the Variscan orogeny. The main graben forming period began in the late Carboniferous, which culminated with rift formation and volcan ...

area. Its two peaks consist of hard rhomb porphyric

lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...

covering softer rocks, forming steep cliffs to the east, south and west.

The name

An old farm beneath the mountain has the name ''Kolsberg''. The first element in this name is the genitive case of the old male name ''Kolr'', and the last element is ''berg'' n 'mountain'. The parish and municipality of Bærum (

Old Norse Old Norse, Old Nordic, or Old Scandinavian, is a stage of development of North Germanic languages, North Germanic dialects before their final divergence into separate Nordic languages. Old Norse was spoken by inhabitants of Scandinavia and t ...

''Bergheimr'') is probably named after this prominent mountain. The last element in the name of the mountain was later changed to ''ås'' m 'mountain ridge' to distinguish it from the name of the farm.

Protected landscape area

The area from Kolsås to

Dælivannet Dælivannet is a lake in Bærum, Akershus county, Norway. It lies just beneath the Kolsås hill on the East side. The lake contains perch and pike and has a rich bird life. The lake has been the subject of paintings and sketches by many signific ...

is a protected landscape area from 1978 (five square kilometers), with four

nature reserve A nature reserve (also known as a wildlife refuge, wildlife sanctuary, biosphere reserve or bioreserve, natural or nature preserve, or nature conservation area) is a protected area of importance for flora, fauna, or features of geological or ...

s: ''Skotta'', ''Dalbo'', ''Kolsåsstupene'' and ''Kolsåstoppen nature reserve''."Naturvernområder i Bærum"
– ''Bærum kommune'' (Retrieved on March 30, 2008)"Snelle-askeskog i Dalbo naturreservat"
(Retrieved on March 30, 2008)

Climbing

Kolsås has been a training area for climbers since beginning of the 20th century. Today it is the largest

rock climbing Rock climbing is a sport in which participants climb up, across, or down natural rock formations. The goal is to reach the summit of a formation or the endpoint of a usually pre-defined route without falling. Rock climbing is a physically and ...

area in the Oslo region. The wall ''Øvre Sydstup'' on the southern wall has more than 200 climbing routes."Klatring på Kolsås i hundre år"
(Retrieved on March 30, 2008)"Kolsås klatreklubb: Klatrefører for Oslo og omegn"
(Retrieved on March 30, 2008)

Winter sports

The northern hillside of Kolsås has alpine skiing facilities. Kolsås from south east

Kolsåsbanen

Kolsåsbanen is part of the subway rail system

Oslo T-bane The Oslo Metro ( no, Oslo T-bane or or simply ) is the rapid transit system of Oslo, Norway, operated by Sporveien T-banen on contract from the transit authority Ruter. The network consists of five lines that all run through the city centre, wit ...

, running from downtown Oslo to Kolsås station, via Gjettum station and Hauger station.

NATO base

The military base ''Kolsås leir'', partly located inside the mountain, was home of NATO's

Allied Forces Northern Europe Allied Forces Northern Europe (AFNORTH) was the northern Major Subordinate Command of NATO's Allied Command Europe (ACE), located at Kolsås outside Oslo. In the case of war with the Soviet Union, AFNORTH would assume supreme command of all Allie ...

(AFNORTH) until 1994."NATO handbook07 uploaded March 25, 1993"
(Retrieved on March 30, 2008)

Culture

The area has occurrences of old

petroglyph A petroglyph is an image created by removing part of a rock surface by incising, picking, carving, or abrading, as a form of rock art. Outside North America, scholars often use terms such as "carving", "engraving", or other descriptions ...

tumuli A tumulus (plural tumuli) is a mound of earth and stones raised over a grave or graves. Tumuli are also known as barrows, burial mounds or ''kurgans'', and may be found throughout much of the world. A cairn, which is a mound of stones buil ...

and

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

quarries A quarry is a type of open-pit mine in which dimension stone, rock, construction aggregate, riprap, sand, gravel, or slate is excavated from the ground. The operation of quarries is regulated in some jurisdictions to reduce their environ ...

. The French painter

Claude Monet Oscar-Claude Monet (, , ; 14 November 1840 – 5 December 1926) was a French painter and founder of impressionist painting who is seen as a key precursor to modernism, especially in his attempts to paint nature as he perceived it. During ...

painted ''Mont Kolsaas'' in 1895."Claude Monet: Mont Kolsaas (1895)"
(Retrieved on March 30, 2008)

References

Landforms of Viken (county) Ridges of Europe Mountains of Oslo {{Viken-geo-stub