An arcuate mountain system of south central Europe,
about 497 miles (800 km) long and 93 miles (150 km) wide,
stretching from the French Riviera on the Mediterranean
coast, through southeastern France, Switzerland, southwestern
Germany, Austria, and Yugoslavia (Serbia). The snow
line in the Alps is approximately 8,038 feet (2,450 m), with
many peaks above this being permanently snowcapped or
hosting glaciers. The longest glacier in the Alps is the Aletsch,
but many landforms attest to a greater extent of glaciation in
the Pleistocene. These include famous landforms such as the
Matterhorn and other horns, aretes, U-shaped valleys, erratics,
and moraines.
The Alps were formed by plate collisions related to the
closure of the Tethys Ocean in the Oligocene and Miocene,
but the rocks record a longer history of deformation and
events extending back at least into the Mesozoic. Closure of
the Tethys Ocean was complex, involving contraction of the
older Permian-Triassic Paleo-Tethys Ocean at the same time
that a younger arm of the ocean, the Neo-Tethys, was opening
in Triassic and younger times. In the late Triassic, carbonate
platforms covered older evaporites, and these platforms began
foundering and were buried under deepwater pelagic shales
and cherts in the early Jurassic. Cretaceous flysch covered
convergent margin foreland basins, along with felsic magmatism
and high-grade blueschist facies metamorphism. Continent-
continent collision-related events dominate the
Eocene-Oligocene, with the formation of giant nappes,
thrusts, and deposition of syn-orogenic flysch. Late Tertiary
events are dominated by late orogenic uplift, erosion, and
deposition of post-orogenic molasse in foreland basins. Deformation
continues, mostly related to post-collisional extension.
See also CONVERGENT PLATE MARGIN PROCESSES; PLATE
TECTONICS; STRUCTURAL GEOLOGY.
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