The Aarmassif or Aaremassif (German: ''Aarmassiv'') is the easternmost

geologic Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth s ...

massif A massif () is a principal mountain mass, such as a compact portion of a mountain range, containing one or more summits (e.g. France's Massif Central). In mountaineering literature, ''massif'' is frequently used to denote the main mass of an ...

in the

Swiss Alps The Alps, Alpine region of Switzerland, conventionally referred to as the Swiss Alps, represents a major natural feature of the country and is, along with the Swiss Plateau and the Swiss portion of the Jura Mountains, one of its three main Physica ...

. It contains a number of large

mountain chain A mountain chain is a row of high mountain summits, a linear sequence of interconnected or related mountains,Whittow, John (1984). ''Dictionary of Physical Geography''. London: Penguin, p 87. . or a contiguous ridge of mountains within a larger mo ...

s and parts of mountain chains.

Name

The massif is named after the

Aar The Aare () or Aar () is the main tributary of the High Rhine (its discharge even exceeds that of the latter at their confluence) and the longest river that both rises and ends entirely within Switzerland. Its total length from its source to i ...

, a river that has its source in the Aarmassif.

Geography

The Aarmassif crops out in the eastern part of the

Bernese Alps The Bernese Alps are a mountain range of the Alps located in western Switzerland. Although the name suggests that they are located in the Berner Oberland region of the canton of Bern, portions of the Bernese Alps are in the adjacent cantons of Va ...

and the

Lepontine Alps The Lepontine Alps (, , ) are a mountain range in the north-western part of the Alps. They are located in Switzerland (Valais, Ticino, Canton of Uri, Uri and Graubünden) and Italy (Piedmont and Lombardy). The Simplon Tunnel, Simplon rail tunnel ...

, roughly from

Leukerbad Leukerbad (, Walliser German: ''Leiggerbad'', although locally known as ''Baadu'') is a municipality in the district of Leuk in the canton of Valais in Switzerland. History The story of Leukerbad dates back to the 4th century B.C. Graves ...

in the west to the

Tödi The Tödi (), is a mountain massif and with the mountain peak Piz Russein the highest mountain in the Glarus Alps and the highest summit in the canton of Glarus, Switzerland. It is located on the border between the cantons of Graubünden, to the ...

in the east. Further east the massif only appears in small

windows Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...

like the ''Vättner window'' between Gigerwald and Vättis in Sankt Gallen and at the Limmerensee in the same canton. The

Grimsel Pass The Grimsel Pass (; ; ) is a mountain pass in Switzerland, crossing the Bernese Alps at an elevation of . The pass connects the Haslital, the upper valley of the river Aare, with the upper valley of the Rhône. In so doing, and as the Aare is a t ...

crosses it.

Tectonics and lithology

The Aarmassif is part of the Helvetic zone of the Alps, which consists of material originally from the European

tectonic plate Plate tectonics (, ) is the scientific theory that the Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago. The model builds on the concept of , an idea developed durin ...

. The Aarmassif has

lithologies The lithology of a rock unit is a description of its physical characteristics visible at outcrop, in hand or core samples, or with low magnification microscopy. Physical characteristics include colour, texture, grain size, and composition. Lith ...

common for

Paleozoic The Paleozoic ( , , ; or Palaeozoic) Era is the first of three Era (geology), geological eras of the Phanerozoic Eon. Beginning 538.8 million years ago (Ma), it succeeds the Neoproterozoic (the last era of the Proterozoic Eon) and ends 251.9 Ma a ...

basement A basement is any Storey, floor of a building that is not above the grade plane. Especially in residential buildings, it often is used as a utility space for a building, where such items as the Furnace (house heating), furnace, water heating, ...

rocks all over Europe, deformed and

metamorphosed Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, causi ...

during the

Variscan orogeny The Variscan orogeny, or Hercynian orogeny, was a geologic mountain-building event caused by Late Paleozoic continental collision between Euramerica (Laurussia) and Gondwana to form the supercontinent of Pangaea. Nomenclature The name ''Varis ...

. Younger

Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...

sedimentary rock Sedimentary rocks are types of rock (geology), rock formed by the cementation (geology), cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or de ...

s were

eroded Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust and then transports it to another location where it is deposited. Erosion is disti ...

from this basement as a

thrust fault A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. I ...

brought the basement to the surface in the

Alpine orogeny The Alpine orogeny, sometimes referred to as the Alpide orogeny, is an orogenic phase in the Late Mesozoic and the current Cenozoic which has formed the mountain ranges of the Alpide belt. Cause The Alpine orogeny was caused by the African c ...

. Other places, where the European basement crops out in the Helvetic zone, are the mountain chains of the

Massif des Écrins Massif des Écrins (; Écrins Massif) are a massif in the French Alps. They form the core of Écrins National Park in Hautes-Alpes and Isère.Mont Blanc Mont Blanc (, ) is a mountain in the Alps, rising above sea level, located right at the Franco-Italian border. It is the highest mountain in Europe outside the Caucasus Mountains, the second-most prominent mountain in Europe (after Mount E ...

in the French and

Italian Italian(s) may refer to: * Anything of, from, or related to the people of Italy over the centuries ** Italians, a Romance ethnic group related to or simply a citizen of the Italian Republic or Italian Kingdom ** Italian language, a Romance languag ...

Alps. The

of the basement rocks are mainly

gneiss Gneiss (pronounced ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. This rock is formed under p ...

es,

schist Schist ( ) is a medium-grained metamorphic rock generally derived from fine-grained sedimentary rock, like shale. It shows pronounced ''schistosity'' (named for the rock). This means that the rock is composed of mineral grains easily seen with a l ...

s and

amphibolite Amphibolite () is a metamorphic rock that contains amphibole, especially hornblende and actinolite, as well as plagioclase feldspar, but with little or no quartz. It is typically dark-colored and dense, with a weakly foliated or schistose ...

s. These were in some places intruded by

Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...

granite Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly coo ...

s after the

, called Aare granite. During a late phase in the Alpine orogeny in the

Tertiary Tertiary (from Latin, meaning 'third' or 'of the third degree/order..') may refer to: * Tertiary period, an obsolete geologic period spanning from 66 to 2.6 million years ago * Tertiary (chemistry), a term describing bonding patterns in organic ch ...

the Aarmassif was uplifted in the form of a large elongated dome structure. The overlying limestones of the

Helvetic nappes The Helvetic nappes ({{langx, de, Helvetische Decken) are a series of nappes in the Northern part of the Alps and part of the Helvetic zone. They consist of Mesozoic limestones, shales and marls that were originally deposited on the southern cont ...

now have a very high dip angle, forming a ridge that appears at the

Eiger The Eiger () is a mountain of the Bernese Alps, overlooking Grindelwald and Lauterbrunnen in the Bernese Oberland of Switzerland, just north of the main watershed and border with Valais. It is the easternmost peak of a ridge crest that extends ...

and south of the

Jungfrau The Jungfrau (, , , "maiden, virgin"), at is one of the main summits of the Bernese Alps, located between the northern canton of Bern and the southern canton of Valais, halfway between Interlaken and Fiesch. Together with the Eiger and Mönc ...

mountain.

References

Geology of the Alps Geology of Switzerland Lepontine Alps {{switzerland-geo-stub

Name

Geography

Tectonics and lithology

See also

References