Lecture Test 1

Geology

Geology

study of the planet earth and the materials of which it is made, and processes that act on these materials, the products formed, and history of the planet

Uniformitarinism

fundamental principle of modern geology

Theory of Plate Tectonics (Internal)

• Lithosphere: broken into plate that move relative to each other sliding on the underlying asthenosphere

• Diverging boundaries and mid-oceanic ridges

• Transform boundary

• converging boundary and subduction zones

• made up of igneous and metamorphic rock

Image: Rock Cycle

Minerals (main characteristics)

• crystalline solid

• occur naturally

• inorganic

• definite chemical composition

Crystalline substance

atoms arranged in regular repeating order

cleavage

property of mineral that allows it to break smoothly along specific internal planes when the mineral is struck

flake cleavage

fragments into very even flat flakes (perimeter of each flake is irregular)

single chain… shares

single oxygen/silica

double chain… shares

two oxygen/silica

sheet structure… shares

more then two oxygen/silica

Important mineral groups:

What is in the FELDSPAR GROUP

• plagioclase (Ca and Na Al silicate)

• Orthoclase (K Al silicate)

Important mineral groups:

What is in the PYROXENE GROUP

• Augite (Ca, Mg, Fe, Al silicate)

Important mineral groups:

What is in the AMPHIBOLE GROUP

• Hornblende (Ca, NA, Mg, Fe, Al silicate)

Important mineral groups:

What is in the QUARTZ

• SiO2

Important mineral groups:

What is in the MICA GROUP

• Muscovite (K, Al silicate)

• Biotite (K, Mg, Fe, Al silicate)

Image: Common Silicate Minerals

Minor Percentage of earths crust:

Complex Al silicate hydroxides with excess negative charge within the layer which is balanced by exchangeable cations… is what group

clay mineral group

Minor Percentage of earths crust:

ex:

• calcite (CaCO3)

• Dolomite (CaMg(CO3)2)

is what group:

Carbonate group

Minor Percentage of earths crust:

ex:

• Gypsum CaSO4 2H2O

  is what group..

Sulphate group

Minerals of Commercial Value:

Native metal group

• give example…

• Au

• Cu

• C (diamond)

Minerals of Commercial Value:

Oxide group

• give example…

• Chalcopyrite CuFeS2

• Sphalerite ZnS

• Galena Pbs

Minerals of Commercial Value:

Phosphate group

• give example…

• Ca F phosphate

Minerals of Commercial Value:

Halide group

• give example…

NaCl

What are physical properties of minerals?

• colour & streak

• specific gravity

• effervescence

• hardness

• lustre

• tenacity

• transparency

• crystal form

• odor

• cleavage

• magnetism

• taste

What are the effects of weathering of minerals

• durability issues

• environmental (acid mine drainage)

Weathering and soil section

Pyrite oxidation produces sulfuric acid, limonite (yellow/brown). Acids react with calcium carbonates to produce gypsum whose crystallization will cause backfill to swell, stone/concrete to crack/burst.

• SLOW PROCESS (10yrs)

MINING - ONTARIO’S ‘RING OF FIRE’

Key points:

• 2002 DaBeers went into Hudson’s Bay looking for precious stones

• discovered copper and zinc instead

• 2008 they found what was a first time commercial quantity of chromite in North America

Rock

a consolidated aggregate of one or more minerals

Igneous Rocks

crystallized from an entirely or largely molten material (magma)

Sedimentary Rocks (describe three ways they could be formed)

Rock formed from

1. lithification of any type of sediment

2. precipitation from solution

3. consolidation of the remains of plants or animals

Metamorphic Rocks (describe how they form)

Formed from pre-existing rocks into a texturally or mineralogically distinct new rock as a result of high temperature, high pressure, or both, but without significant melting

• No melting

Igneous Rocks:

• what did they originate from

• molten material mainly in the upper mantle

• magma if below the earth’s surface

• lava if extruded above earth’s surface

What are igneous rocks classified based on

Composition and

texture:

• grain size is the most important textural characteristic

Igneous Rocks:

Texture:

• explain fine grained (aphanitic)

• Mineral grains <1mm

• Volcanic or extrusive rocks (cool quickly); intrusive rocks that cooled quickly

• Glassy texture (obsidian)

Igneous Rocks:

Texture:

• explain coarse grained (phaneritic)

• Mineral grains >1mm

• Plutonic Rocks (intrusive, cooled slowly)

Igneous Rocks:

Texture:

• explain Porphyritic

• extrusive rock in which large crystals are enclosed in a matrix of fine grained minerals or obsidian

• two episodes of crystallization

• large crystals are called phenocrysts

Igneous Rocks:

Texture:

• explain Pegmatitic

• crystals are very large (cm-m)

• form during the last stages of granitic magma solidification

Igneous Rocks:

Texture:

• explain Pyroclastic

• welded fragments from eruption

• tuff (fine grained)

• volcanic breccia (larger pieces of volcanic rock)

MARS ROVER IMAGE

• bomb sag preserved in layered rocks on the lower slopes of Home Plate

• Bomb sags form in volcanic explosions on Earth when rocks ejected skyward by the explosion fall into soft deposits, deforming them as they land

Igneous Rocks:

Composition:

• explain Felsic

• give examples

igneous rock having abundant light coloured minerals

ex:

• quartz

• k-feldspar

• muscovite

• plagioclase (sodium)

Igneous Rocks:

Composition:

• explain Mafic

• give example

igneous rock having abundant dark coloured of ferromagnesium minerals

ex:

• biotite

• amphibole

• pyroxene

• olivine

• plagioclase (calcium)

Image: Classification of igneous rocks (textbook)

Image: Classification of igneous rocks (lab manual)

Image: How igneous rock form

Name one of the largest valcanoes extending from B.C. to N. Calif

Mount St. Helenes

Image: Intrusive and extrusive igneous rock bodies

Image: Tectonic setting where igneous rocks form

INDONESIAN VOLCANO ERUPTS, LEAVING AT LEAST 13 DEAD

• mount semeru on the indonesian island of Java erupted

• many people had burns, dozen dead, hundreads displaced

• flow of hot gas clouds had stopped amid rain on sunday, by urged caution

• breathing in polluted air is dangerous

• authorities asked citizens to put off returning to several areas

• 127 active volvanoes in indonesia

• indonesia is on the the ring of fire where a series of tectonic fault lines around the pacific that produce frequent earthquakes and eruptions

• eruptions at mount semeru have been recorded since 1818 with a spike in activity in 2000s

• Deadliest erruptions three were in indonesia

  • krakatau in 1883 (caused a tsunami and killed 26 000)

  • tambora in 1815 (killed 92 000)

  • kelut in 1586 (killing 10 000)

what are the two factors that determine the degree of violence or explosiveness of an eruption

1. amount of gas in the lava or magma

2. the viscosity of the lava that determines the ease with which the gas escapes to the atmosphere

Acidic Magma (felsic)

very viscous and explosive

Basaltic Magma

low viscosity and less explosive

What is the composition of volcanic gas

water vapour + SO₂, H₂O, CO₂, HCl

Volcanic Hazards

lava and pyroclastic flows, mudflows, ash eruptions

Types of Volcanoes

• describe a Shield volcanoe

  • give an example of where it is found

• broad, gently sloping cones (2-10) constructed of solidified lava flows

• lava of low viscosity (basaltic)

• found in hawaii islands

Types of Volcanoes

• describe a Cinder Cones

• constructed of pyroclastic ejected from a central vent

• slopes of approx. 30

• much smaller than shield volcanoes

Types of Volcanoes

• describe a Composite Volcano

  • give example

• constructed of alternating layers of pyroclastic and rock solidification from lava flows

• intermediate slopes, built over long periods of time and becomes very large

• mainly andesite

• ex: mount st helens

ST HELENS

• in spring of 1980 a series of ash emissions blackened the peak and the north slope had developed a prominent bulge

• the current summit is a point along the crater rim

• crater is 2000 ft deep and mile wide

• may 18 1980 was the eruptions.

Igneous Intrusions:

• define Discordant Intrusion

not parallel to any layering in the country rock

Igneous Intrusions:

• define Concordant Intrusion

parallel to any layering in the country rock

Igneous Intrusions:

• define Volcanic Neck

magma solidified within the throat of volcano

Igneous Intrusions:

• define Dike

tabular discordant intrusive structure

Igneous Intrusions:

• define Sill

tabular concordant intrusive structure

Igneous Intrusions:

• define Stock

small discordant pluton (body of igneous rock that crystallized at considerable depth) with outcrop area of <100km²

Igneous Intrusions:

• define Batholith

a large discordant pluton (>100km²); formed of numerous, coalesced plutons called diapirs

DARK AND LIGHT COLOURED SILLS

A: the dark coloured rock layer in this photo is a sill made of gabbro

• in upper Brock River Canyon

DARK AND LIGHT COLOURED SILLS

B: dark mafic sill in mountains made of lighter coloured sedimentary rock

• dry valleys area of antarctica

LIGHT AND DARK - COLOURED DYKES

A: dykes of felsic composition cut through dark-coloured mafic volcanic rocks

• near Lakelse, BC

LIGHT AND DARK - COLOURED DYKES

B: Dark-coloured dyke of mafic composition cuts through ligh-coloured granitic rocks

• north of sudbury

Igneous Activity and Plate Tectonics

• what is Mid-oceanic ridge

• diverging plate boundary

• basaltic magma erupts and forms pillow basalts and oceanic crust

Igneous Activity and Plate Tectonics

• what is Intraplate Activity

  • give example

• plate overrides a hot mantle plume

• where the plates move and are most likely to cause earthquakes and erruptions

  • ex: hawaiian volcanism (oceanic plate)

Igneous Activity and Plate Tectonics

• what is Converging boundaries

• intermediate and felsic magma

• an area on Earth where two or more lithospheric plates collide

Metamorphism

the solid state (without melting) transformation of pre-existing rock into texturally or mineralogically distinct new rock as a result of high temperature, high pressure

Name the two main types of metamorphism

Regional and Contact

List the main factors controlling the characteristics of metamorphic rocks

1. composition of parent rock

2. temperature and pressure during metamorphism

3. tectonic forces

4. effects of fluids (ex. water)

METAMORPHIC EVIRONMENT

illustration showing geothermal gradient and its role in metamorphism

• geothermal gradient is lowered by the subduction of comparatively cool oceanic lithosphere

• thermal heating is evident where magma intrudes the upper crust

Image: Metamorphism by heat, pressure, and hydrothermal fluids

Image: When rocks get buried they experience confining pressure that is equal in all direction

• rock becomes more dense and remain non foliated

Regional Metamorphism

• what is the result of high temperatures and pressure

• list four reasons

1. foliation (parallel alignment of the textural and structural features of a rock)

2. new compact minerals

3. recrystallization

4. plastic flow contorts layers and other constituents (pebbles)

Image: in places like convergent plate boundaries rocks experience differential stress

• they may have fracture or fold and develop rock cleavage and foliation of platy minerals

Contact Metamorphism

• what is the dominant factor with relatively low confining pressures (<10 km burial depth)

High temperatures

Metasomatism

1. change in the composition of a rock as a result of the introduction or removal of chemical constituents.

Hydrothermal rocks

rocks formed by precipitation of ions derived from hydrothermal solutions

Image: metamorphic rock identification (based on the degree of foliation and grain size

TUNNELLING AND ROCK DRILING UNDER HIGH STRESS CONDITIONS AT THE NATHPA-JHAKRI HYDRO PROJECT

• Main sliding and creeping surfaces coincide with this foliation which is encountered in a series of quartz-mica-schists, schistose quartzites and amphibolites

define sediment

loose solid particles that originate from

• weathering and erosion of pre-existing rocks

• chemical precipitation from solution

how are sedimentary rocks classified

• size

• rounding

• composition

• transportation (rivers, currents, wind, glaciers, rounding and sorting of sediment)

• Preservation (need to ‘protect’ sediments from re-erosion

• Lithification (transformation of sediments into rock

  • compaction - water forced out

  • cementation - precipitation of cements around grains

• Deposition (sedimentation)

  • velocity is too low to carry clasts

  • solution becomes saturated

Image: material is often deposited in beds (layers or strata)

Law of super position: within a sequence of undisturbed sedimentary rocks, the oldest layers are on the bottom, youngest are on the top

Sedimentary Rocks form from:

• Lithification of sediment (clastic rocks)… give other examples

• quartz

• sandstone

• greywacke

• arkose

Sedimentary Rocks form from:

• Precipitation from solution (chemical)… give other examples

• limestone

• dolomite

Sedimentary Rocks form from:

• Consolidation of the remains of plants or animals (organic)… give other examples

• coal

Image: successive stages of coal formation

Image:

a: chert commonly forms beds and blob-shaped nodules. This chert nodule in dolostone near hamilton ON

• contains fossil sponge, the silica-rich skeleton of which acted as a “seed” for dissolved silica to precipitate around

Image:

b: banded iron formation from northern ON

• shows the alternating bands of magnetite/hematite (purple) and iron-bearing chert (red)

List what sedimentary structures would look like

• bedding planes & original horizontality

• cross-bedding

• graded bed

• mud cracks

• ripple marks

• cut & fill structures

Image:

Bedding Planes: cretaceous strata exposed near Drumheller, Alberta illustrate the characteristic layering of sedimentary rocks. These dark coloured beds are composed of organic-rich mudstone, whereas the light-coloured beds are composed of sandstone

Image: Classification of Sedimentary Rocks - Detrital

Image: Classification of Sedimentary Rocks - Chemical and Biochemical

Image: How to classify sedimentary rocks

Define Relative Dating

rocks placed in their proper sequence of formation

Define absolute dating

actual time in history when something took place

Explain the Principle of Uniformitarianism

geological processes operating in the present are the same processes that have operated in the past

Explain the law of superposition

within a sequence of undisturbed sedimentary rocks, the layers get younger going from bottom to top

Explain the principle of original horizontality

beds of sediment typically deposited in horizontal layers

Explain the principle of cross cutting relationships

a disrupted pattern is older than the cause of the disruption