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Rock Types

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Igneous – solidification of magma

Sedimentary – lithification of sediments

Metamorphic – change of state by pressure and heat

Petrology – the science of rocks and how they are formed

 Rock Types

 

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Rock Types

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Rock Types

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95%

5%

sedimentary

Relationship at the ground surface

Igneous and metamorphic

 Rock Types, distribution

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Igneous Rocks

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iClassified nto three groups depending on amount ofsilicondioxide (SiO2):

• Basic magmas (SiO2

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 Igneous Rocks

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Igneous Rocks

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Igneous Rocks

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Characteristics:

• High strength•  jointed

• Exfoliation joints (basalt columns, ”onion skin”)

• Large crystals (slow cooling at large depth)

• Small crystals (quick cooling)

• Porphyric structure (mixture of slow and quick cooling)

 Igneous Rocks

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Igneous Rocks

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Jan 2008/UHSoil- and Rock Mechanics Prof. U Håkansson

 Igneous Rocks, Granite

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Sedimentary Rocks

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Sedimentary Rocks

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- Formed by lithification of sediments

• Shale (50%)

• Sandstone (35%)

• Limestone (15%)

 Sedimentary Rocks

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Sedimentary Rocks

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PEAT BROWN COAL

MUD MUDSTONE

MORRAINE TILL

GRAVEL CONGLOMERATE

SAND QUARTSITE

ARCOSSILT

SAND-

STONE

GREYWACKE

Particle size [mm]

CLAY SHALE

LIME MUD (MARL) MARLSTONE

LIME LIMESTONE, DOLOMITE

VULCANIC ASH TUFF

LAVA BASALT

 Na-K-Ca salt EVAPORITES

2

0.06

0.002

Resulting

rock type

Genetic background

 Sedimentary Rocks

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Characteristics:

• Great variety• Low strength

• Prone to weathering

•  Altered• Water bearing

 Sedimentary Rocks

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Sedimentary Rocks

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Sedimentary Rocks

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Metamorphic Rocks

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Metamorphic Rocks

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Metamorphic Rocks

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Metamorphic Rocks

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Characteristics:

• Great variety• Variable strength

• Foliated

• Linear 

 Metamorphic Rocks

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Metamorphic Rocks

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Jan 2008/UHSoil- and Rock Mechanics Prof. U Håkansson

 Methamorphic Rocks, Gneiss

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Rock Types, properties

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Rock types, characteristics

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Rock types, characteristics

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Rock Types, mechanical properties

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Destructive mechanisms

Water – erosion, chemical weathering Wind – erosion, mechanical weathering

Frost, ice – erosion, mechanical weathering

Temperature – thermal stresses

Gravity - landslides

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• Mechanical – mainly in arctic and dessert areas

• Chemical – everywhere, but increasing towards equatorialareas

• Biological – e.g. humus acids

 Destructive mechanisms, Weathering

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Destructive mechanisms, Erosion

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h E

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Jan 2008/UHSoil- and Rock Mechanics Prof. U Håkansson

 Destructive mechanisms, Erosion

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D i h i E i

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Destructive mechanisms, Erosion

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D t ti h i W th i

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Destructive mechanisms, Weathering