Rocks materials of the solid earthchapter 2

What types of Rocks are there?Igneous Rocks: from magma or lava Origin: igneous activity • Example: granite or basalt Sedimentary rocks: from sediments Origin: weathering and erosion E

What is a Rock?

How would you define a rock and a mineral?

What types of Rocks are there?

Igneous Rocks: from magma or lava

Origin: igneous activity

• Example: granite or basalt

Sedimentary rocks: from sediments

Origin: weathering and erosion

Example: sandstone or clay

Metamorphic rocks: from stress

Origin: mountain building

Example: gneiss or marble

The rock cycle (page 45)

PART – I: IGNEOUS ROCKS

FEEDBACK:

From what process igneous rocks from?

Plate Margins

• Divergent: Plates pull apart

Example: Mid ocean ridge; Rift

• Convergent: Plate come together

– Ocean – Continent; Ex: Cascades, Andes – Ocean – Ocean; Ex: Japan, Caribbean

– Continent – Continent; Himalaya

• Transform Fault: Plates slide

Origin of Magma (page 228)

Magma forms at three major geological

settings:

• Divergent (Ex: Mid ocean ridge)

• Convergent (Ex: Cascades volcanoes)

• Intra plate Not a plate margin (Ex: Hawaii,

Hot spot)

Origin of Magma (page 148)

Mid Ocean Ridge (divergent)

Subduction Zone (Convergent)

Causes of Magma Formation

Decompression Melting (opening a bottle of soda)

Factors influencing magma formation:

1 Heat Increase

2 Reduction of confining Pressure

Role of volatiles (gases)

Types of Igneous rocks

 Magma cools and crystallizes

Inside the crust → Plutonic or Intrusive rocks

Lava cools and crystallizes

Outside the crust → volcanic or extrusive rocks

Classification of Igneous rocks

Rate of Cooling and Crystal Size

• Texture is size and arrangement of crystals

• Crystal size is determined by the rate and

depth of cooling of magma/lava

• Slow rate forms large crystals

• Fast rate forms microscopic crystals

• Very fast rate forms glass

Types of Textures

Phaneritic: Coarse grain/slow cooling rate

Example: Granite or Diorite

Aphanitic: Fine grain/fast cooling rate

Example: basalt or rhyolite

Glassy: glasslike/very fast cooling rate

Example: Obsidian (volcanic rock)

Types of Textures

Porphyritic: Slow then rapid cooling

Example: porphyry basalt, porphyry granite

Vesicular: Full of holes due to gases

Example: Vesicular basalt, scoria, and pumice

Pyroclastic: Angular volcanic fragments cemented by ash from violent eruptions

Example: tuff

Photomicrograph

What’s the texture?

What’s the texture?

What’s the texture?

What’s the texture?

What’s the texture?

Obsidian Aztec

Temple Mayor, Mexico

Chemical Classification of Igneous

rocks

• Bowen's reaction series (page 53):

• Minerals form in a systematic order

through

Discontinuous series (Olivine to Quartz) and

Continuous series (Feldspars series)

• Magmatic Differentiation

First to form settle at the bottom

• Can Olivine and Quartz be found together in the same rock?

• Why? …

Naming Igneous rocks

Granitic or Felsic rocks

• Light-colored rocks

• Rich in silica/poor in Fe and Mg

• Form from melting of continental crust

• Common rock is Granite (intrusive) or Rhyolite

(volcanic)

Naming Igneous rocks

Basaltic or Mafic/ultramafic Rocks

• Dark Rocks

• Rich in Fe and Mg/poor in silica

• Originate mostly from the oceanic crust at

mid-ocean ridge , and the upper mantle

• Common rock is Basalt (volcanic) or Gabbro

(plutonic)

Texture? Mafic or Felsic?

Texture? Mafic or

Felsic?

Naming Igneous rocks

Intermediate or Andesitic Rocks

• Mineral and chemical composition are average of felsic and

mafic rocks

• Has dark minerals (pyroxene, amphibole, and mica) and light

minerals (feldspar and quartz)

• Silica content: 50%<SiO2 <60%

• Common rock is Andesite (volcanic) or Diorite (intrusive)

• Found mostly at Suduction Zone

Naming Igneous Rocks

 Ultramafic Rocks

• Dark rocks

• Very poor in silica : SiO2 <45%

• Originates from lower mantle and is found in oceanic floor at

mid-ocean ridge along mafic rocks

• Typical rock is peridotite (intrusive) or Komatiite (volcanic)

Classification of igneous rocks

PART – II: Sedimentary rocks

FEEDBACK

From what geological process sedimentary

rocks form?

Weathering

Two kinds of weathering

1 Mechanical weathering

• Breaking of rocks into smaller pieces

• Processes of mechanical weathering

• Frost wedging (freezing and thawing/exfoliation)

• Unloading (exposure to surface)

• Biological activity (burrow animals)

Frost wedging (page 55)

Joint-controlled weathering

in igneous rocks

Unloading and exfoliation

of igneous rocks

Weathering

Two kinds of weathering

2 Chemical weathering

• Alters the internal structures of minerals by

removing or adding elements

• Most important agent is water

• Oxygen dissolved in water oxidizes materials

• Carbon dioxide (CO2) dissolved in water forms carbonic acid and alters the material

Factors of weathering

Important factors

• Climate (heat and moisture)

• Chemical weathering is most effective in areas of

warm temperatures and abundant moisture

Chemical Weathering

Weathering of granite minerals

• Weathering of potassium feldspar produces clay

Classifying sedimentary rocks

• Two groups based on the source of the

material

1 Detrital rocks (Residual solid material)

• Common rocks include

• Shale ( fine grained)

• Sandstone (medium grained)

• Conglomerate (round coarse grained)

• or Breccia (sharp coarse grain)

Classification of

Shale with plant fossils

Sandstone

Conglomerate

Classifying sedimentary Rocks

2 Chemical Sedimentary rocks

once in solution and

precipitates to form sediment Two groups:

A – Chemical Organic Rocks

 From biochemical processes; the

most common sedimentary rocks:

Example: Limestone is the most abundant chemical rock

• Coal: from plants-peat-bituminous coal-lignite-anthracite

Fossiliferous limestone

B - Chemical Inorganic rocks

Chemical Sedimentary Rocks

From precipitating solutions

• Evaporites: Salt or gypsum rocks,

• Through increase in concentration:Hematite , chert , flint , jasper , or agate

Rock salt

Features of Sedimentary rocks

Features of sedimentary rocks

• Strata , or beds (most characteristic)

• Bedding planes separate stratas

• Fossils

• Are traces or remains of prehistoric life

• Are the most important inclusions

• Help determine past environments

• Are used to determine age of sedimentary rocks

• Are used for rock correlation

PART – III: Metamorphic Rocks

FEEDBACK:

• What process forms metamorphic rocks?

• Where would you expect to find

metamorphic rocks?

• Florida or Georgia? Why?

Metamorphic rocks

Are changed from other rocks, including

other metamorphic rocks

• “Every metamorphic rock has a parent rock “

Metamorphism occurs between 200C – 800C at several kms depth

Causes and Types of

metamorphism?

Heat from magma → Contact metamorphism

 Pressure (stress) → Regional metamorphism

• Confining pressure : from burial

• Differential stress: during mountain building

• Chemically active fluids

• Water and other volatiles (Hydrothermal fluids)

Types of pressure (stress) in

metamorphism

Metamorphic Grades

Degrees of metamorphism

• Low-grade (where shale becomes slate)

• Medium-grade (where granite becomes gneiss)

• High-grade (rock partially melts → migmatite)

Metamorphic Textures

 Nonfoliated from contact metamorphism

Typical rocks: Marble and Quartzite

Resembles a coarse-grained igneous rock

Is localized around intrusion

Marble – a Nonfoliated metamorphic rock

Development of foliation due

to directed pressure

Gneiss typically displays

a banded appearance

Classification of metamorphic rocks

Resources from rocks

and minerals

Nonmetallic mineral resources

• Make use of the material’s

• Nonmetallic elements

• Physical or chemical properties

• Two broad groups

• Building materials (e.g., limestone, gypsum)

• Industrial minerals (e.g., fluorite, corundum, sylvite)

End of Chapter 3

1 - The Texture of an igneous

rock is

a Shape of the crystals

b Size and arrangement of crystals

c How hard of soft the rock feels

d All of the above

e I have no idea

2 – Texture of igneous rocks is

determined by

a Pressure and temperature

b Amount of sulfur in the magma

c Rate of cooling of magma

d Depth of cooling of magma

e c and d only

3 - The slower the rate of

cooling, the …

a Smaller the crystals of the rock

formed

b Larger the crystals

c No relation whatsoever

4 - Which terms characterize a

basalt?

a Felsic/Light colored/silica rich

b Mafic/dark colored/silica poor

c Felsic/dark colored/silica rich

d Mafic/light colored/silica poor

5 - Name the volcanic rock (s)

6 - Is this rock:

a: Plutonic? Or b: Volcanic?

7 – Porphyritic-aphanitic is

what type of rock?

a Plutonic with two rates of

cooling

b Volcanic with two rates of

cooling

c None of these

8 – Where to find a basaltic

magma?

a On the continental crust mainly

b On the Oceanic crust

c At the mid-ocean ridge

d At subduction zone

e b and c

9 –Which texture indicates a

magma rich in gases?

10 –Which texture indicates two

11 – Where to find a felsic

magma?

a At mid ocean ridge

b On the ocean floor

c On the continental crust

d At subduction zone

12 –Which term means

13 - Texture?

a: Glassy Or b: Pophyritic

14 - Which texture means all

17 – In what type of metamorphism

do pressure and temperature work

together?

a Contact metamorphism

b Regional metamorphism

c All of the above

d None of the above

20 -What type of weathering is

a Chemical weathering

b Mechanical weathering

c Soil sampling

d a and b

e None of the above

What type of weathering is

oxidation?

22 - Exfoliation results from

THE END

THAT’S ALL FOLKS! THANK YOU!!!