The Aarmassif or Aaremassif (German: Aarmassiv) is a geologic

Geology

Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...

 massif

Massif

In geology, a massif is a section of a planet's crust that is demarcated by faults or flexures. In the movement of the crust, a massif tends to retain its internal structure while being displaced as a whole...

 in the Swiss Alps

Swiss Alps

The Swiss Alps are the portion of the Alps mountain range that lies within Switzerland. Because of their central position within the entire Alpine range, they are also known as the Central Alps....

. It contains a number of large mountain chains and parts of mountain chains.

Geography

The Aarmassif crops out

Outcrop

An outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. -Features:Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficial deposits are covered by a mantle of soil and vegetation and cannot be...

 in the eastern part of the Bernese Alps

Bernese Alps

The Bernese Alps are a group of mountain ranges in the western part of the Alps, in Switzerland. Although the name suggests that they are located in the Bernese Oberland region of the canton of Bern, portions of the Bernese Alps are in the adjacent cantons of Valais, Lucerne, Obwalden, Fribourg and...

 and the Lepontine Alps

Lepontine Alps

The Lepontine Alps are a mountain range in the central part of the Alps. They are located in Switzerland and Italy .On the north the upper Rhône valley separate them from the Bernese Alps and the Furka Pass and the upper Reuss valley separates them from the Urner Alps; on the west the Simplon Pass...

, roughly form Leukerbad

Leukerbad

Leukerbad 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 and ceramics attest the presence of habitation in Leukerbad...

 in the west to the Tödi

Tödi

The Tödi , or Piz Russein, is 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 and Glarus...

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

Window (geology)

thumb|right|350px|Schematic overview of a thrust system. The [[fault |hanging wall block]] is called a [[nappe]]. If an [[erosion]]al hole is created in the nappe that is called a window. A [[klippe]] is a solitary outcrop of the nappe in the middle of autochthonous material.A tectonic window...

 like the Vättner window between Gigerwald and Vättis in Sankt Gallen

Canton of St. Gallen

The Canton of St. Gallen is a canton of Switzerland. St. Gallen is located in the north east of Switzerland. It covers an area of 2,026 km², and has a population of . , the population included 97,461 foreigners, or about 20.9% of the total population. The capital is St. Gallen. Spelling...

 and at the Limmerensee in the same canton

Cantons of Switzerland

The 26 cantons of Switzerland are the member states of the federal state of Switzerland. Each canton was a fully sovereign state with its own borders, army and currency from the Treaty of Westphalia until the establishment of the Swiss federal state in 1848...

.

Tectonics and lithology

The Aarmassif is part of the Helvetic zone of the Alps, which consists of material originally from the European tectonic plate. The Aarmassif has lithologies

Lithology

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, such as colour, texture, grain size, or composition. It may be either a detailed description of these characteristics or be a summary of...

 common for Paleozoic

Paleozoic

The Paleozoic era is the earliest of three geologic eras of the Phanerozoic eon, spanning from roughly...

 basement

Basement (geology)

In geology, the terms basement and crystalline basement are used to define the rocks below a sedimentary platform or cover, or more generally any rock below sedimentary rocks or sedimentary basins that are metamorphic or igneous in origin...

 rocks all over Europe, deformed and metamorphosed

Metamorphism

Metamorphism is the solid-state recrystallization of pre-existing rocks due to changes in physical and chemical conditions, primarily heat, pressure, and the introduction of chemically active fluids. Mineralogical, chemical and crystallographic changes can occur during this process...

 during the Variscan orogeny

Variscan orogeny

The Variscan orogeny is a geologic mountain-building event caused by Late Paleozoic continental collision between Euramerica and Gondwana to form the supercontinent of Pangaea.-Naming:...

. Younger Mesozoic

Mesozoic

The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...

 sedimentary rock

Sedimentary rock

Sedimentary rock are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution....

s were eroded

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...

 from this basement as a thrust fault

Thrust fault

A thrust fault is a type of fault, or break in the Earth's crust across which there has been relative movement, in which rocks of lower stratigraphic position are pushed up and over higher strata. They are often recognized because they place older rocks above younger...

 brought the basement to the surface in the Alpine orogeny

Alpine orogeny

The Alpine orogeny is an orogenic phase in the Late Mesozoic and Tertiary that formed the mountain ranges of the Alpide belt...

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

Massif des Écrins

The mountains of the Massif des Écrins form the core of the Écrins National Park in France.-Mountains:*Barre des Écrins 4102 m*La Meije 3983 m*Ailefroide 3954 m*Mont Pelvoux 3946 m*Pic Sans Nom 3913 m*Pic Gaspard 3883 m*Le Râteau 3809 m...

 and of Mont Blanc

Mont Blanc

Mont Blanc or Monte Bianco , meaning "White Mountain", is the highest mountain in the Alps, Western Europe and the European Union. It rises above sea level and is ranked 11th in the world in topographic prominence...

 in the French

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 and Italian

Italy

Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

 Alps.

The lithologies

Rock (geology)

In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...

 of the basement rocks are mainly gneiss

Gneiss

Gneiss is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from pre-existing formations that were originally either igneous or sedimentary rocks.-Etymology:...

es, schist

Schist

The schists constitute a group of medium-grade metamorphic rocks, chiefly notable for the preponderance of lamellar minerals such as micas, chlorite, talc, hornblende, graphite, and others. Quartz often occurs in drawn-out grains to such an extent that a particular form called quartz schist is...

s and amphibolite

Amphibolite

Amphibolite is the name given to a rock consisting mainly of hornblende amphibole, the use of the term being restricted, however, to metamorphic rocks. The modern terminology for a holocrystalline plutonic igneous rocks composed primarily of hornblende amphibole is a hornblendite, which are...

s. These were in some places intruded by Permian

Permian

The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...

 granite

Granite

Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...

s after the Variscan orogeny

Variscan orogeny

The Variscan orogeny is a geologic mountain-building event caused by Late Paleozoic continental collision between Euramerica and Gondwana to form the supercontinent of Pangaea.-Naming:...

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

Tertiary

The Tertiary is a deprecated term for a geologic period 65 million to 2.6 million years ago. The Tertiary covered the time span between the superseded Secondary period and the Quaternary...

 the Aarmassif was uplifted

Tectonic uplift

Tectonic uplift is a geological process most often caused by plate tectonics which increases elevation. The opposite of uplift is subsidence, which results in a decrease in elevation. Uplift may be orogenic or isostatic.-Orogenic uplift:...

 in the form of a large elongated dome structure

Dome (geology)

In structural geology, a dome is a deformational feature consisting of symmetrically-dipping anticlines; their general outline on a geologic map is circular or oval...

. The overlying limestones of the Helvetic nappes

Helvetic nappes

The Helvetic zone, Helvetic system or the Helveticum is a geologic subdivision of the Alps. The Helvetic zone crops out mainly in Switzerland, hence the name . Rocks in the Helvetic zone are sedimentary and were originally deposited at the southern margin of the European plate...

 now have a very high dip

Strike and dip

Strike and dip refer to the orientation or attitude of a geologic feature. The strike line of a bed, fault, or other planar feature is a line representing the intersection of that feature with a horizontal plane. On a geologic map, this is represented with a short straight line segment oriented...

 angle, forming a ridge that appears at the Eiger

Eiger

The Eiger is a mountain in the Bernese Alps in Switzerland. It is the easternmost peak of a ridge crest that extends across the Mönch to the Jungfrau at 4,158 m...

 and south of the Jungfrau

Jungfrau

The Jungfrau is one of the main summits in the Bernese Alps, situated between the cantons of Valais and Bern in Switzerland...

mountain.