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, 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 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 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. 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 and of
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 Alps.
The
lithologies 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
Variscan orogeny, 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 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 mountain.
See also
*
Infrahelvetic complex
References
Geology of the Alps
Geology of Switzerland
Lepontine Alps
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