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The diverse rocks of Switzerland

Switzerland has igneous, sedimentary and metamorphic rocks. These three rock types are closely connected to each other in a continuous cycle.

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“The Rock Cycle – The Rock Cycle Explained Simply – What Are Rocks? – Endogenous Forces”, Source: YouTube, Die Merkhilfe (in German)

Rocks are formed, altered and then break down again in a continuous cycle. Accordingly, there are three types of rocks: igneous, metamorphic and sedimentary rocks. Rocks basically consist of mineral components, which also include natural glasses. They can also contain originally organic material such as animal remains or plant components. Learn more about Switzerland’s rocks in the following sections.

To realise a deep geological repository, Nagra has to obtain a profound knowledge of suitable rocks and their properties. Learn more about these rocks on a guided tour through the Swiss underground rock laboratories.

The rock cycle

The rocks within the uppermost 30 to 60 kilometres of the earth, the earth’s crust, are in a continuous cycle.

These cyclical movements are mostly so slow that we are not aware of them. Mountains form, and the rocks exposed at the surface are weathered. The mountains are eroded, and the debris is carried off in rivers and deposited elsewhere. Sedimentary rocks are formed from the eroded material.

All rocks can reach great depths where they melt or are altered to form metamorphic rocks. The molten rock, or magma, solidifies at depth or at the earth's surface as magmatic rock, and the cycle begins anew.

Rock cycle
Rocks form in a slow cycle between the earth's surface and the deep crust.

1. Igneous rocks

When magma cools in the earth’s crust, it solidifies to form plutonic rocks such as granite. Magma from volcanoes that reaches the earth's surface is termed lava. This solidifies to form volcanic rocks such as basalt. Some magma also rises from below through narrow dykes and rock fissures. If this magma does not reach the surface and remains and solidifies in the dykes, dyke rocks such as aplite and lamprophyre form as a result.

Island magmatisches Gestein Säulenbasalt
Basalt columns form due to the delayed cooling of lava. There are no examples of these impressive columns in Switzerland – all the basalts are metamorphic and were overprinted by heat and pressure deep in the earth’s interior. Photo: Nagra

Examples of magmatic rocks in Switzerland


Granite (plutonic)

granit
Habkern granite, Habkern (Canton Bern). Photo: Earth Science Collections of the Swiss Federal Institute of Technology Zürich, Urs Gerber

Occurrence: Alps, crystalline basement beneath the Swiss Plateau and Jura Mountains
Origin: Slow cooling of magma at depth, resulting in large interlocking crystals
Main minerals: Feldspar, quartz, mica
Appearance: Light, speckled, massive
Properties: Grainy, very hard, in some locations with joints and dykes
Uses: Floor and façade tiles, blocks for road and waterway engineering, gravestones


Volcanic basalt

basalt
Metamorphic basalt from Alp Flix (Canton Graubünden). Photo: Earth Science Collections of the Swiss Federal Institute of Technology Zürich, Urs Gerber

Occurrence: Common worldwide, metamorphic in Switzerland
Origin: Rapid cooling of lava at the earth's surface, and hence not fully crystallised
Main minerals: Pyroxene, hornblende, olivine, feldspar
Appearance: Dark grey to black, massive
Properties: Sharp-edged, brittle, weathering-resistant
Uses: Glass wool production, cobblestones


Aplite and lamprophyre dyke rocks

aplit
Aplite dyke (light) in gneiss (dark), Bergell (Italy). Photo: Earth Science Collections of the Swiss Federal Institute of Technology Zürich, Urs Gerber

Occurrence: Solidified magma in rock fissures
Origin: Rapid cooling of lava at the earth's surface, and hence not fully crystallised
Main minerals (aplite): Quartz, light mica
Main minerals (lamprophyre): Feldspar, hornblende, pyroxene, dark mica
Appearance (aplite): Light and fairly fine-grained
Appearance (lamprophyre): Dark and fine- to medium-grained
Properties: Hard, easily workable
Uses: Limited use in Switzerland


2. Sedimentary rocks

Sedimentary rocks are formed from materials (e.g. eroded material from mountains, mud, sand or salt) deposited on land or in the water where they gradually solidify. The originally loose components are cemented together with time to form solid rocks. Sedimentary rocks are often layered. Conglomerates, such as nagelfluh, sandstone and clay, consist of eroded material from mountains. Limestones are formed mainly from shells and other hard parts of sea creatures. Chemically formed sediments, such as gypsum and rock salt, are formed when marine and lacustrine waters evaporate.

wasserschloss
New sediments are being formed here. Rivers transport rock debris to the plains where they are deposited. With time, these loose gravel deposits form a solid nagelfluh. Photo: Nagra

Examples of sedimentary rocks in Switzerland


Nagelfluh (conglomerate)

nagelfluh
Nagelfluh, Gottschalkenberg (Canton Zug). Because of its appearance, nagelfluh is also called “concrete of the good Lord”. Photo: Earth Science Collections of the Swiss Federal Institute of Technology Zürich, Urs Gerber

Occurrence: Mainly at the alpine margin
Origin: In the Alps, rocks are reduced to debris by erosion. Rivers transport this material into the foreland and deposit it in the Molasse Basin
Composition: Gravels from different alpine rocks (e.g. granite, limestone), cemented and solidified into a fine-grained ground mass
Properties: Forms ridges and steps in the landscape


Sandstone

sandstein
Mica sandstone with chestnut leaf, Kreuzlingen (Canton Thurgau) Photo: Earth Science Collections of the Swiss Federal Institute of Technology Zürich, Urs Gerber

Occurrence: Swiss Plateau and Alps
Origin: Deposition in river channels and the sea
Composition: Mainly quartz grains and rock fragments, mostly cemented with limestone
Appearance: Grey, rarely red, green and yellow, fine-grained
Properties: Easily workable, often low durability
Uses: Building bricks, façade tiles, road surfacing, stone masonry


Molasse marl

molassemergel
Molasse marl, Eriz near Thun (Canton Bern) Photo: Earth Science Collections of the Swiss Federal Institute of Technology Zürich, Urs Gerber

Occurrence: Swiss Plateau and alpine margin
Origin: In river plains and the sea
Composition: Very fine-grained mix of calcite, clay and other mineral and rock grains
Appearance: Multi-coloured, layered
Properties: Mostly dense, soft after weathering at the earth's surface
Uses: Brickwork products


Clay

opalinuston
Opalinus Clay from the Mont Terri Rock Laboratory (Canton Jura) Photo: Earth Science Collections of the Swiss Federal Institute of Technology Zürich, Urs Gerber

Occurrence: Jura and northern parts of Switzerland and the Alps
Origin: Deposition in the sea
Composition: Clay minerals, quartz, little calcite
Appearance: Varicoloured, often layered
Properties: Soft, dense; clay minerals swell on contact with water
Uses: Sealing clay for disposal sites and dams, production of clay bricks and cement


Limestone

Öhrlikalk
Öhrlikalk, Öhrlisattel (Canton Appenzell Innerrhoden). Photo: Collection Urs Oberli, St. Gallen

Occurrence: Jura and Alps
Origin: Deposition of hard parts of organisms on the sea floor
Composition: Mainly calcite
Appearance: Mostly light- to blue-grey, fine-grained
Properties: Easily workable
Uses: Floor tiles, building bricks, cement production, lime plaster


Anhydrite and gypsum

Anhydrit und Gips
Anhydrite between clayey shale (below) and gypsum (above), Simplon Tunnel (Canton Valais). Photo: Earth Science Collections of the Swiss Federal Institute of Technology Zürich, Urs Gerber

Occurrence: Tabular and Folded Jura, Alps
Origin: Precipitation from seawater due to evaporation
Main minerals: Gypsum and anhydrite; gypsum contains confined water, anhydrite is anhydrous
Appearance: White to dark-grey, coarse-grained, banded
Properties: Soft
Uses: In the construction industry as gypsum plaster, special gypsum, plasterboard, production of cement and porous concrete, modelling and moulding plaster, production of sulphuric acid


3. Metamorphic rocks

Increased pressure and temperature deep underground result in the transformation of all types of rocks to metamorphic rocks by changing their structure or composition. This can lead to the formation of new minerals that can grow in a preferred direction, namely perpendicular to the largest pressure component.

Granit Felslabor Grimsel
Metamorphic rock structures at the Grimsel Test Site. Photo: © Comet Photoshopping, Dieter Enz

Examples of metamorphic rocks in Switzerland


Gneiss

gneis

Occurrence: Alps, crystalline basement beneath the Swiss Plateau and Jura Mountains
Origin: Rock altered by increased pressure and temperature, produced from granite for example
Main minerals: Feldspar, quartz, mica
Appearance: Light speckling, thick-layered with augen structure due to orientation of minerals
Properties: Weathering-resistant, fissile. Can be strongly fractured and penetrated by dykes
Uses: Kerbstones, building bricks, floor and façade tiles, roofing


Schist

schiefer
Hornblende-Garbenschiefer, Val Tremola (Canton Ticino). Photo: Earth Science Collections of the Swiss Federal Institute of Technology Zürich, Urs Gerber

Occurrence: Alps, crystalline basement beneath the Swiss Plateau and Jura Mountains
Origin: Metamorphosis of clay-rich parent rock
Main minerals: Mainly mica with a variety of other minerals
Appearance: Shiny, dark, thin-layered due to mineral orientation
Properties: Easily fissile along smooth cleavage planes
Uses: Floor and façade tiles, roofing


Marble

marmor

Occurrence: Alps
Origin: Transformation (metamorphosis) of limestone and dolomite
Main minerals: Calcite (lime marble), dolomite (dolomite marble)
Appearance: Grainy, light, partly banded
Properties: Easily workable
Uses: Floor and façade tiles, tiling, sculptures


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