GEOL 1340 FINAL EXAM REVIEW.txt

UNIT 1

### INTRODUCTION

SCIENTIFIC STUDY OF EARTH - GEOLOGY

the branch of science concerned with the physical structure and substance of the earth, the processes which act on these, and the earth’s development since formation.

UNIT 2

### MINERALS

HOW DO MINERALS FORM?

- solidification from melt
- precipitation from solution
- bioprecipitation
- solid-state diffusion
- direct precipitation from vapor

WHAT IS A MINERAL?

naturally occurring, inorganic, crystalline solid that has a specific chemical composition.

WHAT DOES IT MEAN TO BE CRYSTALLINE?

regular, repeating, and orderly.

EXAMPLES OF ORDERLY CRYSTAL STRUCTURE

we often use models to depict crystalline structures of minerals

- ball and stick
- geometric figures

TYPES OF BONDS

ionic (electrons transferred)

covalent (electrons shared)

metallic (van der Waal’s forces)

SPECIFIC CHEMICAL COMPOSITION

which elements? what proportion?

MOST ABUNDANT ELEMENTS IN EARTH’S CRUST

1. Oxygen (O) 47%
2. Silicon (Si) 28%
3. Aluminum (Al) 8%
4. Iron (Fe) 5%
5. Calcium (Ca) 4%
6. Sodium (Na) 3%
7. Potassium (K) 3%
8. Magnesium (Mg) 2%

these eight constitute 98% of the weight of the crust.

most minerals are silicates

- i.e. contain combinations of Si and O
- silicates total >90% of earth’s crust

silicates are most common minerals because Si and O are the most available elements.

SILICATE MINERALS - (SiO4)^-4 ← negative charge

strong bond within the tetrahedron (implication?)

bonding among SiO4 tetrahedra defines major structure types of silicates.

- how are the tetrahedra arranged? How many adjacent O do they share?
1. isolated
2. single-chain
3. double-chain
4. sheet
5. framework

OTHER MAJOR MINERAL CLASSES: NON-SILICATES

1. carbonates (CO3)
2. sulphides (S)
3. sulfates (SO4)
4. oxides (O, O2)
5. phosphates (PO4)
6. chlorides (Cl)

and others…

most are classified by their anion

also… native elements

CARBONATES - MAJOR EXAMPLES

calcite (CaCO3) the most common non-silicate mineral ; dolomite (CaMg(CO3)2)

- the rocks limestone, dolomite, and marble are made of calcite and dolomite.

SULPHIDES - MAJOR EXAMPLES

pyrite (FeS2) ; Galena (PbS) ; sphalerite (ZnS) ; Chalcopyrite (CuFeS2)

SULPHATES - A MAJOR EXAMPLE

Gypsum (CaSO4*2H2O)

CHLORIDES

halite (NaCl) ; sylvite (KCl)

NON-SILICATES: NATIVE ELEMENTS

silver ; copper ; sulphur ; diamond (C) ; graphite (C) ; gold

PHYSICAL PROPERTIES OF MINERALS

examples of physical properties

- colour
- streak
- hardness
- specific gravity
- crystal form
- cleavage (preferred directions of breakage)

AND MANY OTHERS

PHYSICAL PROPERTIES REFLECT…

identity of atoms (chemical composition)

arrangement of atoms

type of atomic bonds

UNIT 3

### 4 INTRO TO ROCKS, CRYSTALLIZATION FROM MAGMA

WHAT DEFINES A ROCK?

- crystalline grains - interlocking crystals
- clastic grains - pressure and natura cement precipitated from water bind rock fragments together
- grains of a rock - mineral crystal fragment or rock fragment

coherent

naturally occurring

aggregate of 1+ minerals

WHY ARE THERE SO MANY DIFFERENT TYPES OF ROCK?

rocks are a product of:

materials, processes, and environment

we name rocks based on their:

composition, texture, and structure

CLASSIFYING AND IDENTIFYING ROCKS

classifying and identifying rocks gives us a basis for understanding the environments in which they formed.

we classify rocks into three basic types:

IGNEOUS

solidify (crystallize) from molten rock (magma)

igneous rocks comprise two major groups:

- extrusive = volcanic rocks
- lava ; pyroclasts
- intrusive rocks

SEDIMENTARY

weathering

is important because this is how we get consolidated sediments, including soil and ions dissolved in water ; decomposition of rock at or near the surface of the earth

- influenced by temperature, water, pressure, etc.
- physical weathering
- chemical weathering

erosion

process where moving liquid water, ice, or wind loosens and moves material

notice the difference between weathering vs erosion

sediment - unconsolidated material (not a rock)

from what can sediment derive?

weathering and erosion can affect any type of rock:

- intrusive and extrusive igneous rock
- a sedimentary rock
- a metamorphic rock
- any kind ca be weathered and eroded

formation of clastic sedimentary rocks - lithification

compaction and cementation

when sediments accumulate, the pressure from the weight of overlying sediments compacts the material.

some mineral, usually calcite or quartz, precipitates from the groundwater to bind the clastic particles. this is the process of lithification.

1. clastic sedimentary rocks
1. physical sedimentary rocks, lithified (compacted and cemented)
2. chemical sedimentary rocks
1. precipitate or crystallize from water solutions
3. biochemical sedimentary rock
1. formed by the accumulation of shells or skeletons of organisms
4. organic sedimentary rock
1. formed from accumulation of carbon rich relics of organisms.

METAMORPHIC

pre-existing rocks crystallize and form new, stable mineral assemblages

solid state reactions

at depth, response to high P & T conditions

- increased T and P with burial
- increased T and P with tectonic forces
- minerals may no longer be in equilibrium

partial melting results in production of new magma

ROCK CYCLE

a concept that we use to visualize the interrelationship among these three major rock types.

HOW DO ROCKS FORMED AT DEPTH END UP ON EARTH’S SURFACE?

exhumation = uplift by tectonic forces + erosion of overlying rocks

which ones form at depth?

- intrusive igneous rocks
- physical sedimentary rocks
- organic sedimentary rocks
- metamorphic rocks

what’s formed at/near the surface?

- extrusive igneous rocks
- chemical sedimentary rocks
- unconsolidated sediments

“DYNAMIC EARTH”

surface is reduced

weathering

- breaks down rock

erosion

- lowers relief
- depletes soil

surface is renewed

tectonic uplift

- raises rock to surface

intrusion and extrusion of magma

- generates new rock

deposition of products of erosion and weathering

DESCRIBING INTRUSIVE BODIES

composition

depth of emplacement - (formed at depth or shallow)

grain size (crystal size), accessory mineral (indicate pressure)

size (large or small)

geometric shape?

follow layering in country rock?

concordant (corresponding in direction with the planes of adjacent or underlying strata → sill

tabular intrusive bodies that crosscut layering → dike (discordant)

INTRUSIONS FORMED AT DEPTH

intrusion formed at considerable depth, we call them plutons

pluton - “plutonic rocks”

- blob shaped, do not follow any layering in the country rock (discordant)

we describe plutons by their size (surface expression)

- stock: outcrop area