Rocks 3 Types of Rocks 1. Igneous Means “from fire” Means “from fire” Forms when magma (molten rock) cools and hardens Forms when magma (molten rock) cools and hardens Magma is called lava when exposed at Earth’s surface Magma is called lava when exposed at Earth’s surface

3 Types of Rocks 2. Sedimentary Erosion creates sediment Erosion creates sediment Sediment deposited by water, ice, and wind Sediment deposited by water, ice, and wind Sediment deposits are compressed and to form sedimentary rock Sediment deposits are compressed and to form sedimentary rock

3 Types of Rocks 3. Metamorphic Formed from extreme heat or pressure Formed from extreme heat or pressure Chemical processes Chemical processes Means “changed form ” Means “changed form ”

Rock Cycle Geologic forces and processes cause rock to change from one type to another Geologic forces and processes cause rock to change from one type to another Become sedimentary by… Become sedimentary by… Erosion, deposition, and cementation Erosion, deposition, and cementation Become Metamorphic by… Become Metamorphic by… Changing temperature and pressure Changing temperature and pressure Become igneous by… Become igneous by… Melting and cooling Melting and cooling

Rock Properties Physical & chemical properties determined by where rock was formed Physical & chemical properties determined by where rock was formed Physical properties reflect chemical composition Physical properties reflect chemical composition Rock stability (chemical properties) affects rate of weathering and breakage Rock stability (chemical properties) affects rate of weathering and breakage Bowen’s Reaction Series Bowen’s Reaction Series How minerals crystallize from magma How minerals crystallize from magma Minerals crystallize at specific temperatures based on their composition Minerals crystallize at specific temperatures based on their composition

Chemical Stability Tendency of a compound to maintain its original composition Tendency of a compound to maintain its original composition Depends on bond strength holding minerals together Depends on bond strength holding minerals together More Si – O bonds make rock more stable More Si – O bonds make rock more stable Physical Stability Physical Stability Zones of weakness based on formation Zones of weakness based on formation Weaknesses allow for weathering Weaknesses allow for weathering

Formation of magma Forms when rock melts Forms when rock melts 3 Factors 3 Factors 1. Temperature – melting point 2. Pressure – low pressure favors melting 3. Presence of fluids in the rock – fluids lower melting point

Igneous Rock - Where magma cools Intrusive igneous rock Intrusive igneous rock Solidifies inside the crust Solidifies inside the crust Extrusive igneous rock Extrusive igneous rock Solidifies on Earth’s surface Solidifies on Earth’s surface Crystal properties Crystal properties Intrusive – slow cooling (Big crystals) Intrusive – slow cooling (Big crystals) Extrusive – fast cooling (Small crystals) Extrusive – fast cooling (Small crystals)

Fractional Crystallization Removal of different minerals from cooling magma at different temperatures Removal of different minerals from cooling magma at different temperatures Magma composition changes as it cools Magma composition changes as it cools

Igneous Rock Texture Igneous rock – Made of crystals Igneous rock – Made of crystals Coarse grained – large crystals Coarse grained – large crystals Fine grained – Small crystals Fine grained – Small crystals Porphyritic Porphyritic Mixture of large & small crystals Mixture of large & small crystals Glassy – small % of dissolved gases Glassy – small % of dissolved gases Vesicular – large % of dissolved gases Vesicular – large % of dissolved gases

Igneous Rock Composition Felsic Felsic Lots of silica (SiO2) Lots of silica (SiO2) Lighter in color Lighter in color Mafic Mafic Less silica Less silica Darker in color Darker in color Rich in Mg & Fe Rich in Mg & Fe Intermediate Intermediate

Intrusive Igneous Rock Structures Batholith Batholith Large formation (100 km 2 ) Large formation (100 km 2 ) Form core of many mountain ranges Form core of many mountain ranges Stock – Small batholith Stock – Small batholith Laccolith Laccolith Intrusion making rock above it become dome shaped Intrusion making rock above it become dome shaped

Sills & Dikes Sill Sill Layer of magma between rock layers Layer of magma between rock layers Parallel to the layers around it Parallel to the layers around it Dike Dike Going through rock layers Going through rock layers Perpendicular to the layers around it Perpendicular to the layers around it

Sedimentary Rocks Formed from sediment Formed from sediment Loose fragments of rock, minerals, organic material that break down Loose fragments of rock, minerals, organic material that break down Characteristics determined by Characteristics determined by Sediment source Sediment source Mode of transport Mode of transport Deposit conditions Deposit conditions

Converting sediment to rock Compaction Compaction Volume & porosity decreased by weight of above sediment Volume & porosity decreased by weight of above sediment Cementation Cementation Minerals precipitate in pore space between sediment grains & binds the grains together Minerals precipitate in pore space between sediment grains & binds the grains together

Sedimentary Rock Classifications 1) Chemical sedimentary rock Formed when minerals precipitate from solution or settle from a suspension Formed when minerals precipitate from solution or settle from a suspension Evaporites Evaporites Minerals left behind after H2O evaporation Minerals left behind after H2O evaporation Gypsum, halite Gypsum, halite

Sedimentary Rock Classifications 2) Organic sedimentary rock Forms from remains of living things Forms from remains of living things Shells of marine organisms Shells of marine organisms Example: Coal, some limestones Example: Coal, some limestones

Sedimentary Rock Classifications 3) Clastic sedimentary rock Made up of rock fragments carried away from source by water, wind, or ice Made up of rock fragments carried away from source by water, wind, or ice Classified by sediment size Classified by sediment size Conglomerate – large rounded fragments Conglomerate – large rounded fragments Breccia – large angular fragments Breccia – large angular fragments Sandstone – sand-sized grains (small) Sandstone – sand-sized grains (small) Shale – clay-sized particles (smaller) Shale – clay-sized particles (smaller)

Clastic Sediment Characteristics Sorting Sorting Sorted according to size Sorted according to size Well sorted – all the same size sediments Well sorted – all the same size sediments Very Poorly Sorted – lots of different sizes Very Poorly Sorted – lots of different sizes Low speed favors well sorted Low speed favors well sorted Great distance favors well sorted Great distance favors well sorted

Clastic Sediment Characteristics Angularity Angularity Angularity relates to “smoothness” and rough edges Angularity relates to “smoothness” and rough edges Particles that move greater distance from source tend to be less angular Particles that move greater distance from source tend to be less angular Closer to source increases angularity Closer to source increases angularity Stratification Stratification Layering of rock Layering of rock

Sedimentary Rock Features Cross-beds and graded beddings Cross-beds and graded beddings Slanting layers Slanting layers Ripple Marks Ripple Marks Found in shallow water areas (beach or river bed) Found in shallow water areas (beach or river bed) Mud Cracks Mud Cracks Shrinking causes drying mud to crack (flood plains, dry lake beds) Shrinking causes drying mud to crack (flood plains, dry lake beds) Fossils & Concretions Fossils & Concretions Hard parts of animal remains Hard parts of animal remains Lumps of rock found in sediments Lumps of rock found in sediments

Metamorphic Rocks Metamorphism Metamorphism The process in which one type of rock changesinto metamorphic rock The process in which one type of rock changesinto metamorphic rock Causes Causes Heat Heat Pressure Pressure Hot fluids Hot fluids

Metamorphism Contact Metamorphism Contact Metamorphism Small area of rock surrounded by magma heat undergoes changes Small area of rock surrounded by magma heat undergoes changes Regional Metamorphism Regional Metamorphism Large area (1000’s of km 2 ) Large area (1000’s of km 2 ) Heat causes minerals to combine chemically to form new minerals Heat causes minerals to combine chemically to form new minerals

Metamorphic Classifications Based on texture Based on texture Foliated Rock Foliated Rock Minerals are arranged in bands or planes Minerals are arranged in bands or planes Compositional banding Compositional banding Nonfoliated Rock Nonfoliated Rock No banding No banding Contains mostly one mineral Contains mostly one mineral Minerals all same shape (No rearrangement) Minerals all same shape (No rearrangement)