Introduction to Rocks

Rock:

a naturally occurring

aggregate of minerals

or mineraloids

Three Rock Classes…

IGNEOUS ROCKS

form from the solidification of molten rock

http://www.physicalgeography.net/fundamentals/images/20011005-0039_DAS_large.jpg

General Classification of Igneous Rocks

Extrusive Rocks(Volcanic)

Intrusive Rocks (Plutonic)

General Classification of Igneous Rocks

MaficFelsic Intermediate

Increasing Fe & Mg

Increasing Si & Al

Igneous Rock Environments

Felsic:Continental

Mafic: Oceanic

Intermediate:Volcanic Coasts

and Islands

Common Igneous Rocks

Fine

Grained

(Extrusive)

Coarse

Grained

(Intrusive)

Felsic Intermediate Mafic

Rhyolite Andesite Basalt

Granite Diorite Gabbro

Three Rock Classes…

SEDIMENTARY ROCKS

form from deposits of weathered pre-existing rock

http://digital-desert.com/mojave-preserve/geology/conglomerate.gif

Physical/Mechanical Weathering

Abrasion

Physical/Mechanical Weathering

Root Wedging

Physical/Mechanical Weathering

Frost Wedging

Physical/Mechanical Weathering

Salt Wedging

http://upload.wikimedia.org/wikipedia/commons/b/ba/Salt_weathering_in_gozo.jpg

Physical/Mechanical Weathering

Exfoliation (Pressure Release)

Chemical Weathering

• Solution

– H2CO3 + CaCO3 → Ca2+

(aq) + 2HCO3-

(aq)

• Dissolution of calcite in carbonic acid

– NaCl → Na+ (aq) + Cl-

(aq)

• Dissolution of halite in water

Chemical Weathering• Hydrolysis

– In hydrolysis a molecule is split into two parts by reacting with water. One product includes an OH- from the water molecule, whereas H+ is added to another

– Mg2SiO4 + 4H+ + 4OH- ⇌ 2Mg2+(aq) + 4OH

- + 4H4SiO4 (aq)• Hydrolysis of olivine results in all products in solution

– 2KAlSi3O8 + 2H2CO3 + 9H2O ⇌ Al2Si2O5(OH)4 + 4H4SiO4 (aq) + 2K+ + 2HCO3

-

• Hydrolysis of feldspar produces clay

)(4481044283 44)(484 aqKSiOHOHOSiAlHOHOKAlSi )(4481044283 44)(484 aqKSiOHOHOSiAlHOHOKAlSi )(4481044283 44)(484 aqKSiOHOHOSiAlHOHOKAlSi

Silicic Acid

(Dissolved Silica)

Chemical Weathering

• Oxidation

– 4FeS2 + 15O2 + 22H2O → 4FeO(OH) + 8SO42- + 16H+

• Oxidation of pyrite to form limonite

General Classification of

Sedimentary Rocks

Clastic

(Broken Pieces)

Chemical

(Precipitated)

http://parkerlab.bio.uci.edu/pictures/photography pictures/Badwater salt flats, Death Valley.jpg

Classification

of Clastic

Sedimentary

Rocks

Conglomerate

Siltstone

Sandstone

Mudstone/Shale

Classification of

Chemical Sedimentary Rocks

Mineral Rock

Calcite… Limestone

Silica… Chert

Gypsum…

Halite…

Evaporite

Hematite… Iron

Formation

Sedimentary Rock Environments

Shale

Sandstone

Evaporite

Limestone

Breccia

Conglomerate

Three Rock Classes…

METAMORPHIC ROCKSform from pre-existing rocks that have been subjected to

heat and pressure

http://farm4.static.flickr.com/3227/2897260233_24897666ba.jpg

Classification of Metamorphic Rocks

Foliated (Banded) Non-Foliated (Massive)

Classification of

Foliated Metamorphic Rocks

Slate Schist Gneiss

Increasing Temperature

Formation of

Foliated Metamorphic Rocks

Shale Gneiss

Mic

roscope

Hand S

am

ple

Schist

Classification of

Non-Foliated Metamorphic Rocks

Quartzite Marble Serpentinite

Sandstone Limestone Peridotite

Formation of

Non-Foliated Metamorphic Rocks

Quartz Sandstone Quartzite

Mic

roscope

Hand S

am

ple

The Rock Cycle

Identifying Rocks

Foliated/Layered Non-Foliated/Non-Layered

Sedimentary Metamorphic Igneous

Identifying Rocks

Grains Crystals

Sedimentary Metamorphic Igneous