EAS 205
Big bang
13.7 Ga ago (billion. Calculated via rate of expansion of universe
Solar Nebula Theory
why the universe is shaped the way it is & explains co-planar orbit of planets.
Shape of universe
Thins in the middle; equatorial bulge
Solar system
Formed 4.6 Ga ago. Nothing HERE is that old. ANy rock that old came here.
Sun
Primary heat source.
Planet formation
Collisions (AKA cold accretion). Composition depends on distance from sun.
Cold accretion
A collision; eventually will run into something.. Either fuses or destroys.
Radioactive decay
generates heat; will form internal layers over time. At time zero, earth was producing 5x more heat
Critical size
temperatures reach a high (1000C) due to gravity constriction. Materials segregate.
Earth’s deserts
1/4 of the surface
Gravitational contraction
Raises internal temperature (>1000C)
Segregation of material
Fe and No sink to core.Lighter elements float to form in crust. Radioactive elements concentrate
Earth’s surface
Always changes
early atmosphere
gravity kept gasses. h20, H2, C0, C02.
Plants about 3.5 Ga
produced 02, around 2 Ga, 02 was ambient in atmosphere
Early water
since the beginning, not liquid until 4 Ga
Oceans proof?
Sedimentary rocks from 4 Ga
Current earth cahanges
Partial melting
Weathering – destroys mafic, enhances felsic crust composition
mafic
darker rock, rich in iron & magnesium. Rusts at surface.
Felsic
rich in silica; doesn’t break down or react at surface. More stable.
Majority of earth’s crust
felsic
Additional mass to the earth
No significant mass. 50 x 10^6 gained a year from meteorites. Lose some too.
Earth’s composition
Crust, upper mantle, lower mantle, core.
Rheologic
HOW DOES IT BEHAVE. Lithosphere, asthenosphere, mesosphere, inner core, outer core.
Lithosphere
Crust and upper mantle
ASthenosphere
rest of upper mantle
mesosphere
upper mantle beneath the asthenosphere and lithosphere
Compositional terms
Crust, Mantle, Core. No division.
Core polarity
Inner is different than outer, so they try and switch places (reversing). happens a lot.
inner core
Solid Fe & Ni, increasing in size.
outer core
Liquid Fe & Ni. Defined by changes in seismic waves. Convection = earth’s magnetic field.
Core
inner & outer core
Middle & top units
mantle & lithosphere
Crust
Upper lithosphere (oceanic & continental, base (moho)
Mantle
Mafic (Fe & Ni. Plastic behavior, lower part contains mesosphere, slow, super hot.
Lithosphere
Uppermost part of mantle + crust. Cold and rigid, elastic. Mostly mafic.
Elastic
Stretch and return to old shape. Temporary deformation. Lithosphere.
Plastic
deformation is permanent; won’t return to old shape. Mantle.
Upper lithosphere
Crust. Coldest and most brittle. Upper 100KM. 10Km in oceans.
Oceanic crust
thinner and more dense; more mafic. 10KM thick.
Continental crust
lighter & very thick. 100Km thick. More felcic. Near the top.
Base of crust
Mohorovic discontinuity. Compositional change. Reflected seismic waves and amplification of seismic waves.
Geological time scale
Fundamental tool to get a history and determine cause of geological events. Uses backtracking.
Backtracking
Relative ages; rock on top can give date for rock on bottom. Principle of superposition.
Principle of superposition
younger stuff is on top
Absolute age
MORE definite dates (every 30 years…)
Quantitative; primarily determined via radiometric dating. Uranium -> lead.
Human age
7 million years; we don’t understand a lot of processes yet
Scientific method
bacon; observe, hypothesize, experiment. Hypotheses get upgraded to theories, then laws.
Atom
smallest unit of chemical element. Can be a lot of things, arrangement determines what. UNDERSTANDING WEAKNESSES WILL ILLUSTRATE WEAKNESSES IN MATERIAL.
Atom contents
Electrons, protons, neutrons
isotope
Same # of protons, different # of neutrons
compound
contains more than 2 elements in fixed proportions
Layers
are weakpoints
Most common elements on Earth
Oxygen and Silicon. Most rocks picked up have silicon.
Other common elements
Aluminim, Magnesium, Calcium, Iron, Sodium
Most common compound
SiO4; silicates. Super stable, not easily broken from each other. breaks off metal easily.
Minerals
Inorganic, naturally occurring solid. Crystalline, fixed or fixed variable limits of composition.
Color
Impurity; easily changed.
Streak
How mineral looks when crushed. Only useful for metallic minerals.
Mohs scale
1-10 hardness scale. 1-3 moved by water. 567 is most common. harder is more stable.
Cleavage
HOW the rock breaks; same every time. How many planes of cleavage?
Fracture
WILL break, but don’t know where. Breaks at weakest section…
Crystal structure
Classic shape ; salt is cubic
Density
darker color means iron; rusting.
Polymorphs
exactly the same chemical composition, SAME structure.
Mineral groups
silicate & non-silicates
silicate
largest, contain Si & O; divided based on crystal structures.
non silicate
composed of one or more elements, does NOT contain Si.
Quartz
Silicate group.
SiO2.
feldspars
Silicate group. Most abundant material in crust. Al, O, Si…
3D framework. Ceramics.
has cleavage
Ferromagnesian silicates
Silicate group. Fe and Mg. Chain/Ring. Black, brown, green. Weather poorly. Mafix.
Clays
Silicate grouping. Sheets that absorb water. NOT a mineral. Floats
Carbonate
NON-silicate. beaches & reefs.
Sulfate
Non-silicate. mobile in groundwater. gypsum.
Sulfides
Non-silicates. Found with iron. Polluting.
Oxides
non-silicate. rusting, magnetite, sought after ores.
halides
Non-silicate. Salts. LOTS in Alberta
native elements
non-silicates. Gold, etc.
Rocks
Solid, cohesive aggregate of crystals or grains of one or more minerals. NOT volcanic glass (non-crystalline) and coal.
3 types of rocks
igneous
sedimentary
metamorphic
igneous rocks
Formed by cooling & solidification of molten material. Isotropic. Non-porous (except pyroclastic)
magma igneous
Intrusive (cools inside earth). Plutonic rocks. Slower cooling; larger crystals.
lava igneous
Extrusive (cooled outside earth). MORE weaknesses. Volcanic. Cools fast; smaller crystals.
Pyroclastic
Came out a volcano. Air bubbles. Weak.
Texture
internal patterns of a rock; orientation & size of grains/crystals INSIDE.
igneous compositions
felsic to mafic. In between = intermediate.
Type depends on proportion of free quartz, Feldspars, Fe-Mg minerals.
Aphanitic
type of igneous rock; cannot see individual crystals
Phaneritic
type of igneous rock; can see individual crystals
Porphyritic
type of igneous rock; started cooling and was shot up
Glassy
type of igneous rock; shot up, cooled too fast, cannot form crystals.
Vesicular
type of igneous rock; shot up from volcano, formed air bubbles/vesicles.
Sedimentary rocks
made from another rocks, organisms or chemical changes. Carried in a fluid, deposited and lithified, or precipitated.
Clastic and Chemical
Lithified
transformed from sediment to rock
Clastic / detrital
type of sedimentary rock; mechanical breakup of other rocks. Named after clast = grain size.

ANISOTROPIC (will not break the same way, but can find weakpoints (where material meets)). porous. Generally hard. 5.5-7

Chemical
type of sedimentary rock; crystals form from precipitation or growth from solution. may have large biological components. mobile. Organic or inorganic, isotropic-anisotropic, soft 2-4, soluble.
SENSITIVE TO WATER AND PH. We build with them.
Conglomerate grains
round against other grains
breccia grains
angled against the grain
>2mm grains
type of sedimentary rock; congolmerate or breccia rock.
2 – >0.0625
type of sedimentary rock; sandstone
0.0625 – >0.004
type of sedimentary rock; silstone, shale
type of sedimentary rock; claystone, musdtone, shale
Organic chemical deposit
type of sedimentary rock; skeletal remains or excretions. Limestone or chalk.
Inorganic chemical deposit
type of sedimentary rock; precipitation due to evaporation.
Metamorphic rocks
made from pre existing rocks; recrystallized without melting, crystals got bigger/rearranged/recomposed. MOSTLY anisotropic, can be iso.
Some characteristics of old rock remain.
Crystaline/BENT LAYERS.
hardish
elongated
NON-POROUS
Types of metamorphic rocks
Caused by changes in pressure or tempertaure, buried.
Contact or regional.
Contact metamorphic
Cooling of a plutonic body (solidified magma chamber). 100’s of meters.
Regional metamorphic
Stress and heating related to plate tectonics. 100’s of KMs.
Fabric
preferred orientation in elongation; is a weakpoint.
Rock Cycle
Transition of a rock into another type via processes:
Weathering, sedimentation, lithification (sedimentary)
Heat & Pressure causing recrystallizing and deformation (metamorphic.
Melting and crystallization (igneous)
Plate Tectonics
Large scale movement of the lithosphere (crust) or asthenosphere (partly molten upper mantle). WHERE THINGS GO WRONG.
Plate Tectonic theories/history
Snider 1855 – Puzzle idea
Wegener 1912 – Continental drift
Du Toit 1937 – Gondwanaland, glacial deposit, ice movment
Visual evidence of plat tectonics
99% of continents fit, similar environment across oceans, marine fossils far from ocean.
Earth’s magnetism
Magnetic minerals align themselves with the magnetic point of earth when at the curie point
Polar wandering curves
60’s, Irving. Alternating strips of magnetic north on ocean floor. Cracked floor, magma pours up, aligns to current magnetic north.
Crust ages
oceanic = 200 Ma
continental = 3.96 Ga
Wilson cycle
opening and closing of the oceans. made super continents. Have had at least 3 of these.
Plate movement
Hot material moves up, little comes through the crust, rest goes to the side. Gravity pulls heavy plate down.
Movement rate & directions
plates move around 2-3 CM a year. hawaii like places move 11.
3 plate types
divergent
transform
convergent
Divergent plate boundary
move apart due to mantle uprising. Tensile thinning, lots of volcanoes in upper 12 KM. Creates new crust. ICELAND.
Transform plate boundary
Plates move past each other; shearing displacement. ripping. LOTS of shallow earthquakes, mostly moderate. No volcanoes. SAN ANDREAS
Convergent plate boundary
Plates bump into each other.
Denser plate subducts; deep trenches, volcanoes, earthquakes.
Lighter plate will obduct; build mountains.
plate collisions
continental-continental = butt heads, huge mountains, volcanoes are hard to reach surface.
oceanic-oceanic – form islands and volcanoes
oceanic-continental – classic; makes rocky mountains.
Earthquakes
Sudden slippage (rupture) along fault zones in response to stress. Seismic slip
Stress
Applied force. 3 types. Compressive, tensile, shearing.
Compressive stress
squishing, subduction zone, goes upwards & makes mountains.
tensile stress
pulling apart; usually applied stress over time. Break is fast. Thinning of material.
Shearing
sliding past, parallel or oblique. San Andrea
Strain
result of stress. Deformation is the observable part. Will be plastic, elastic, or a rupture. IS measurable.
Low Temperature and Pressure
near surface, elastic, ruptures.
High Temperature and Pressure
Usually deep, 100KM+, long term stress, plastic. Rupture. If cold enough.
Main Mechanism of Earthquakes
Reid’s elastic rebound theory. San Francisco 1906.
Earthquake sequence
Elastic deformation prior to failure.
Sudden displacement along fault.
Elastic rebound as rick snaps back to previous dimensions.
Creep
Movement; gradual. material isn’t sticking together. Means stress is being released. Non violent. AKA aseismic slip.
Hypocentre
AKA = focus. Point on the fault of the first movement. Normally far down. Energy goes in ALL directions, but not necessarily equally.
Epicenter
Surface ABOVE the focus. Not guaranteed to be where the energy is.
Deep focus earthquakes
Surface intraplate
All plate boundaries
Shallow focus earthquakes
Within & below 100KM of the lithoshere
Compressional boundaries (subduction zones)
Seismic wave types
Body (P & S waves). Travel from focus to recorder through earth’s guts.
Surface waves (Rayhleigh & Love). Travel from epicenter to recorder via surface.
P waves
PRIMARY. PUSH. COMPRESSIONAL. Travel through anything. Fastest. Slowed down by gas and liquid. Bounce.
S waves
SECODNARY. SHAKE. SHEAR. More of a wiggle. Slower. ONLY travel through solids. Used to map oil/gas. Greater distance between P and S; further away the quake.
Rayleigh waves
Vertical motion, rolling of the ground.
Love waves
Side to side; PROBLEM. Rip buildings. Only affect near epicenter.
Early seismographs
Concerned with direction the quake came from. Tsunami warning.
Current Earthquake detection
Ground displacement measurement. Measure vertical, E-W, N-S on 3 different machines. Lag of P and S triangulates center.
Magnitude
Quantitative. Richter and Moment Magnitude scale.
Intensity
Qualitative. How bad did it shake? Observations of the effects.
Richter
Quantified measure of strength of an earthquake. Logarithmic. largest wave amplitude. PROBLEM is a huge # wind up as 7.x. not useful over 7. Only measures energy passing through things.
Moment magnitude scale
measure energy released at sight of slippage.
Measure rigidity, area of fault, amount of slip.
Earthquake damage
Depends on building materials/codes, POV, geology, coincidental weather, response time of help
Charleston USA earthquake
Intensity got higher, and lower, and higher with distance. Ground material matters.
Primary effects of Earthquake
Effects CAUSED by the actual earthquake. Violent ground motions.
Secondary effects of Earthquake
Effects TRIGGERED by earthquake. lasts longer. Tsunami, Landslides, Fire, Liquefacation, Disease
Tsunamis
Disruption and displacement of sea floor. 1000kph. Increases in frequency as approaching shore. High magnitude =/= mean tsunami
IOTWS
Indian ocean Tsunami Warning System. ? Monitors sea level data and the rate of lateral change
Issue warnings, including expected time of arrival and possible wave
heights
Only works if the tsunami originates far enough away
Fire from Earthquakes
Usually more damaging than the quake itself. Water lines are often broken.
Landslides
Some material is prone to slipping, quake is just the trigger. Most ground isn’t “Stable”.
Flores
Volcanic island that had coastline collapse.
Liquefaction
Change in arrangement of water in structure of clay/sand. Shaking makes a slurry. Common in marine clays (they are held together by salt).
Sand boil
Sand from below mixes with water, becomes less dense, floats up. Rolls downhill.
Disease
Results from loss of sanitation, shelter, contamination,
Earthquake prediction
With pattern recognition, we can estimate when events make an earthquake likely.
Risk assessment principles
Assume stresses act continuously. Faults with lots of seismic activity ARE safer. Look for seismic gaps/earthquake cycle.
Short term prediction
Compare changes to normal background noise.
Precursor phenomena:
Drops in seismic waves
Uplift/tilting ground
Increased radon in water
Geophysical changes
Anomalous animals
Increase in ground temperature.
Controlling strain release
#1 fluid injection – lubricate fault system. Rocky mountain chemical pumping.
#2 Explosives – release small quakes. Or HUGE ones. Liability issues.
Bedrock foundations
doesn’t shake buildings as much
Dewater areas
Remove excess water. Want SOME. too much is the issue.
Slack in linear structures
Accommodate seismic activity. Pipelines that will move.
Fluid magma temperature
750-1100 Centigrade
Composition of magma
Depends on geography. SiO2, Fe, Mg, others.
Amount of SiO2 in magma
determines melt type, melt viscosity, gas release ability.
Partial melting
rock types determine what melts. Little bits will melt and head towards low pressure.
Magma gas release
More SiO2 makes for cooler, more viscous magma that hardens faster, and traps gas.
Places to avoid during volcano
Areas with silicate rich magma (continental & water rich material)
Subduction zones
Continental hot spots/mantle plumes
Hot spots
Stationary locations in planet; plates move over top. Possible sites of heat making radioactive elements.
Types of mafic volcanic eruptions
Fissure, shield, cinder cones
Mafic eruptions
Runnier (less silica), so less volatile.
Fissure eruption
Majority of all volcanic activity; occurs along spreaking ridges and drifts, low hazard/risk.
Shield volcanos
Is a fracture(s). Multiple exit points; one main vent fed by multiple feeders. No guarantee WHERE it will erupt.
Not very viscous, flows downhill easily, covers a lot of area.
Kilawaya; lots of activity. Watch at night to see activity.
Hawaii is actually 10KM high and 100KM across!
Cinder cones
Found with various compositions
? Common with gaseous mafic lavas
? Small (generally ? Fairly symmetrical, steep sided (~35°) cones
don’t really hold lava. Pimples on the island. SHORT LIVED features. Lava in area is viscous and gassy.
ONE vent. Plugs up itself. Pressure blows it up.
Flood basalt
Shallow dipping slopes
? Thick and spatially extensive
Lots of lava, extends over a large period of time. They formed the hawaiian islands.
Affect the climate.
Shield Volcano
Is a fracture(s). Multiple exit points; one main vent fed by multiple feeders. No guarantee WHERE it will erupt.
Not very viscous, flows downhill easily, covers a lot of area.
Volcanic dome
Felsic, intermediate. High, steeped. Made of volcanic rubble. Cools rapidle.
Composite volcano
? AKA stratovolcanoes
? Intermediate to felsic lavas
? Steep sided, large and explosive
? Layered
? Related to subduction zone
Snow and ice.
Calderas
? Large, negative features
? NOT restricted to volcano type or composition
? Eruption is sudden and often catastrophic
? Formed by one of two methods: 1)Phreatic eruption
2)Collapse

Do NOT erupt frequently. When they do erupt, it is bad ass.

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Phreatic eruption
? Explosion caused by water boiling in pores and fractures
? Generally occurs in volcanoes adjacent to or surrounded by water
? Example: Krakatau, Indonesia 1883
All eruptions are phreatic, technically.
Collapse eruption
? Rapid emptying of the magma chamber during eruption
? Chamber collapses Example: Mt. Mazama, Oregon ~6800 BP
Primary volcano effects
– Lava
– Pyroclastic material
– Lahars*
– Toxic gases
– Phreatic eruptions
– Earthquakes
Hazard maps
Define risk zones based on history
Pyroclastics
? Hot, fragmented, welded or solidified volcanic material
? Range from ash (1/16 mm) to bombs and blocks (house-sized)
? Eruption can cause shockwaves
? Types:
? Volcanic ash eruption
? Volcanic ash flow (Nuees ardentes)
Volcanic ash eruption
? Mainly ash and dust (Very soft; pulverized glass and rocks. Gets everywhere.
Just like lime; mixes with water and becomes concrete. Is
super acidic. Slippery. Super heavy when wet.
Volcanic ash flows
AKA: nuees ardentes; grey eruptions
• Hot, dense clouds of ash and gases
• Speeds can easily exceed 100 km/hr
• Temperatures often >1000°C
• Unpredictable
• Generally associated with composite volcanoes
most common death of volcanologists.
Lahars
Both a primary and secondary event. Causes flooding
elsewhere, as it displaces water.
Happens when you have sources of water near the
eruption. Downhill; follows any drainage patters.
SUPER thick. Will pick up stuff. Things float really well;
like buildings.
Primary = melting snow and ice
Secondary = ash has fallen and rain begins
Toxic gasses
Rare to kill; mostly bad luck. Do not generate enough to kill people.
? Generally dense like CO and CO2 .
? Not usually a problem
? Build up in water may be a hazard
Volcanic fog/smog – VOG
Gasses & particles of ash. Parts of
volcanic national parks are often closed from vog
Secondary Volcanic effects
? Indirectly caused by the eruption
? Usually atmospheric, but there are others!
? Short or long-term
? Duration depends on layer of atmosphere or size of land area
affected
? Severity depends on amount of material ejected
? Localized or widespread
Volcanic 2ndary atmospheric effects
If in the stratosphere:
? Affects are global and long-term
? Affects global temperatures (blocks sunlight)
If in the troposphere:
? Local temperature changes and effects
? Short-term (
Acid rain
SO2 from sulphide gases emitted during the eruption
? In troposphere: removed as acid rain
? In stratosphere: stays for years
? Can circle the globe
? May cause ozone depletion
Primary lahar
ash with water (melted snow and ice)
Secondary lahar
ash with rain from volcano
Volcano classification
3, now 4 ways
Active, Dormant, Extinct, Erupting.
Active – last 10,000
Dormant – not in last 10,000. CAN still erupt. Long wait.
Extinct – Unlikely to ever erupt again. Cinder cone… ON TOP OF something active.
Harmonics
swarms in earthquakes. Sudden increase.
harmonics; two signatures. A type is rocks
breaking. B type is the harmonic; often masked,
sound of magma moving.
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