Geol 121

Sort these geologic time scales from longest to shortest:
Epoch, era, eon

Eon, Era, Epoch

What are the 4 layers of the Earth?

crust, mantle, outer core, inner core

What are the 3 Earth systems?

climate system, geodynamo, plate tectonics

Who proposed the idea of plate tectonics?

Alfred Wegener (1912)

What is the geodynamo system?

rapid motion of the liquid outer core stirs up electrical flow in the solid (iron) inner core - causing Earth's magnetic field

What are the 3 types of plate boundaries?

divergent, convergent, transform

types of divergent boundaries

oceanic and continental

oceanic divergence

Rifting, volcanoes, earthquakes

Continental divergence

rift valleys, volcanoes, earthquakes

Types of convergent boundaries

ocean-ocean, ocean-continent, continent-continent

ocean-ocean convergence

oceanic trench, volcanic island arc, deep earthquakes

ocean-continent convergence

volcanic mountain chain, folded mountains, and deep earthquakes

continent-continent convergence

crustal thickening, folded mountains, and earthquakes

Types of transform-fault boundaries

Mid-ocean ridge, continental

Mid-ocean ridge transform fault

lateral faults, earthquakes (ocean)

continental transform fault

lateral faults, earthquakes (continental)

What is subduction?

When one plate descends beneath the other

What are the 2 mantle convection theories?

Whole-mantle convection
Stratified convection

How do minerals form?

When magma cools
When water vapour precipitates
When there are changes in temp. and pressure in existing materials

What are the most common classes of minerals?

silicates, carbonates, oxides, sulfides, sulfates

What are physical properties of minerals?

Hardness, cleavage, fracture, luster, streak, crystal habit

Types of rocks

igneous, sedimentary, metamorphic

Igneous rock

Formed through crystallization of magma and lava

Sedimentary rock

Formed through deposition, burial and lithifaction

Metamorphic rock

Formed through re-crystallization of new minerals in solid state

extrusive igneous rock

formed from magma that erupts and rapidly cools

intrusive igneous rock

formed when magma intrudes into unmelted rock

Felsic

- feldspar and silica
- high silica content
- quartz, rhyolite, granite

Mafic

- magnesium and iron (ferric)
- low silica content; high magnesium, iron and calcium
- gabbro, basalt

Bowen's Reaction Series

a model of fractional crystallization

What mineral crystallizes first in Bowen's Reaction Series?

olivine

What mineral crystallizes last in Bowen's Reaction Series?

quartz

Plutons

large igneous bodies deep in the crust
range from 1 cubic km to 100+ cubic km
batholiths are largest forms

Sills

magma injected between layers of country rock
concordant (parallel) to country rock

Dikes

routes of magma transport
cut across country rock layers (disconcordant)

Physical weathering

fracture and fragmentation

Chemical weathering

chemically altered or dissoved

siliciclastic sediments

coarse grained, medium grained, fine grained

Examples of coarse grained rocks

gravel, conglomerate

Examples of medium grained rocks

sand, sandstone

Examples of fine grained rocks

silt, mud, clay, shale

Types of sedimentary basins

rift, thermal subsidence, flexural

Rift basins

deep, narrow, and long, with thick successions of sedimentary rocks and extrusive and intrusive igneous rocks

Thermal subsidence basin

conductive cooling of the mantle thickens the lithosphere and causes it to decrease in elevation

Flexural basin

when the weight of the overriding plate causes the underlying plate to bend and flex

Continental environments

lake, alluvial, desert, glacial

Shoreline environments

delta, beach, tidal flats

Marine environments

deep sea, continental shelf, organic reefs, continental margin/slope

Cross-bedding

- beds deposited by wind or water
- up to 35 degrees from horizontal

Graded bedding

- most abundant in continental slope and deep-sea sediments
- deposited by muddy currents

Ripples

- very small ridges of sand or silt at 90 degrees to current
- found in sand and ancient sandstone

Burial

- sediments repeatedly buried under new layers
- subjected to high T&P and chemical changes

Diagenesis

physical and chemical changes that convert sediments to sedimentary rock

Compaction

major physical change that decreases volume and porosity of sediment

Cementation

chemical change that takes place when minerals precipitate in the pores between sediment particles and bind together

Causes of metamorphism

- internal heat of Earth
- internal pressure
- fluid composition inside Earth

Role of temperature in metamorphism

- temp increases with depth
- can use rock's mineral composition as geothermometer

Geothermal gradient

- the rate of change in temperature with depth
- average 30 C/km of depth

Confining pressure

Stress that is applied uniformly in all directions.

Directed pressure

force exerted in a particular direction

types of metamorphism

regional, contact, seafloor, burial, high pressure, shock

regional metamorphism

- most widespread
- high T&P imposed over large areas of crust
- usually along ridge boundaries

contact metamorphism

- very local
- heat from igneous intrusion metamorphoses rock

seafloor metamorphism

result of hot seawater circulating through basalt

burial metamorphism

deposition of overlying sediment forces rock down

high-pressure metamorphism

- occurs at great depth
- 8 to 12 kbar

shock metamorphism

- meteorite impact
- high T&P alters surficial rock

Metamorphosis and plate tectonics

Occurs at:
- plate/continental interiors
- divergent plate margins
- convergent plate margins
- transform plate margins

metamorphosis at plate/continental interiors

contact, burial, regional

metamorphosis at divergent plate margins

seafloor, contact

metamorphosis at convergent plate margins

regional, high-pressure, contact

metamorphosis at transform plate margins

seafloor and shearing along transform faults

Stratigraphy

the study of rock layers and the sequence of events they reflect

Principles of Stratigraphy

Original Horizontality, Superposition, Faunal Succession

original horizontality

sediments are deposited in horizontal layers

superpositon

the higher the layer, the younger it is

Faunal Succession

sedimentary strata in an outcrop contain fossils in a definite sequence

4 eons of geologic time

Hadean, Archean, Proterozoic, Phanerozoic

Hadean Eon

- formation of Earth
- 4.56 bya to 3.9 bya

Archean Eon

- geodynamo and primitive climate system established
- primitive single celled microorganisms
- 3.9 bya to 2.5 bya

Proterozoic Eon

- plate tectonics and climate system similar to present
- oxygen releasing microorganisms
- 2.5 bya to 542 mya

Phanerozoic Eon

- marked by appearance of shelled fossils
- 542 mya to present
- comprised of 3 eras:
1. Paleozoic
2. Mesozoic
3. Cenozoic

Stable Interior

- Canadian shield is biggest part
- mostly PreCambrian rock
- consists of domes and basins

Basin

circle/oval depression where sediments are thicker than surrounding area

Domes

areas where platform sediments have been uplifted and eroded to expose the basement rock

Blue ridge province

- Precambrian rocks were thrust on top of younger sedimentary rock
- i.e. old rock on top of young rock

Piedmont

- metamorphosed Precambrian and Paleozoic rock intruded by granites and thrust over Blue ridge rocks

Coastal plain

- relatively undisturbed sedimentary rock
- began accumulating 180 mya

magmatic addition

magma pouring into oceans and creating new land

Continental accretion

- the growth of a continent along its edges
- happens when continents smash into each other

accreted terrain

foreign pieces of crust forcefully attached to continental margin

exotic terrain

- block of land that collided with a continent along a convergent margin and attached to the continent
- exotic \= not originally part of the continent to which it is now attached.

Volcano

Hill or mountain constructed from the accumulation of lava and other erupted material

volcanic geosystem

The total system of rocks, magma, and interactions needed to describe the entire sequence of events from melting to eruption.

Basaltic lava

Product of mantle melting
Produced along mid-ocean ridges, continental rift valleys and hot spots within plates
1000-1200 degrees C
Extremely fluid; flows fast and far

Types of basaltic lava

Pahoehoe
Aa
Pillow Lava

Pahoehoe

Highly fluid lava
Coiled folds look like rope

Aa lava

rough, jagged blocks
Slow moving
High viscosity

Pillow lava

formed underwater
indicates that a region on dry land was once underwater

Andesitic lava

Intermediate silica content
Produced in volcanic mountain belts above subduction zones