EOSC 114 – Final Review Notes
Unit 1: A Fragile System
Explain what density is & how it relates to stratification.
o Density = mass/volume; how much mass fits into a space. Unit: kg/m 3
o Stratification = less-dense materials float on top of denser materials
This is found in the atmosphere, the ocean, the earth, etc.
Explain why disaster scales are based on the Order-of-Magnitude concept, and interpret graphs with logarithmic
o Without using a log scale, sometimes a graph will be too large.
o “Orders of magnitude” are powers of 10 – a logarithmic graph steps by powers of 10
Converting an exponential curve into a logarithmic graph will give a linear graph.
o Many disaster scales use powers of 10: Richter, Fujita, Torino, Beaufort, etc.
Relate natural-disaster risk & intensity to frequency, return period, and consequences (costs).
o Risk = probability severity * cost of damage ($ + human lives)
o Intensity is inversely proportional to frequency.
o Return period = average number of years between disaster events of the same magnitude
RP (M) = time span of data / # of cases of magnitude M.
Explain how some recent disasters were associated with concentration or dilution of energy.
o Time scales for energy to build up and release
Concentration of energy Dilution of energy
Earthquakes: years -> minutes Tsunami: minutes -> hours
Volcanoes: decades -> days Floods: hours -> days
Hurricanes: months -> days
Storms: hours -> minutes
Rogue waves: hours -> seconds
Get the disaster info you need from reliable sources.
Compare tectonic, rock, hydrologic, and biogeochemical cycles.
o Involves the creation -> movement -> destruction of plates
o One cycle can last more than 200 million years!
o Types of plate boundaries
Divergent: two plates move away
Forms: large, underwater mid-ocean ridges
Rifts formed through seafloor spreading
Convergent: two plates collide
Subduction zone: one plate moves beneath another (usually ocean and continental)
At 100-120 km, melts and releases H2O and CO2 -> hot enough to cause lower crust to
melt -> magma moves up -> reaches surface -> erupts
Movement along a transform fault – most are beneath oceans but some are on continents
o Rock: aggregate of one or more minerals. Mineral: naturally occurring crystalline substance w/ specific
o Rock Cycle: recycling of three major groups of rock
Crystallization of molten rock -> igneous rock beneath/on Earth’s Surface
Weathering -> sediment Sediment is transported by wind/water/ice to depositional sites
Buried -> lithification -> sedimentary rock
Chemically active fluids + heat + pressure cause metamorphic rock to be formed
Eventually, temp high enough -> melt -> restart
o Cycling of water from oceans -> atmosphere -> continents -> back again
o Driven by solar energy
o Residence time: estimated avg time a drop of water spends in any part of the cycle
Only a tiny fraction of earth’s water is active at a certain time – often stored
Only ~.3% of all water important for life -> groundwater
o Cycling of an element/elements through atmosphere/lithosphere/hydrosphere/biosphere
Related to the other cycles
Tectonic provides water + gas, heat + energy. Rock and hydrological transfer and store.
Elements and chemicals are transferred via storage compartments/reservoirs
When a biogeochem cycle is understood, the rate of transfer (flux) among all components is known
List the 1st and 2nd most common elements in the earth, ocean, and atmosphere.
Elements Earth Crust Ocean Atmosphere
1 most common Fe O O N
2 most common O Si H O
3 most common Ni Al Cl Ar
Describe how viscosity and compressibility relate to the phase of matter.
o Fluids: Easily flow, change shape easily = gases, liquids
o Viscosity: measure of how much fluids resist flowing or changing their shape.
Greater viscosity, more resistance. Depends on temperature + chemical structure.
o Compressibility: ability to be squeezed/expanded. Results in a change in density because of volume change.
o Phases of matter
Solids: Not fluid, not very compressible.
Liquids: Very fluid, not very compressible.
Gases: Very fluid, very compressible.
Be able to diagnose the type of strain by the way a material deforms.
o Strain: Change in shape or size of a solid object (deformation)
Elastic: Ability to change shape when forced but spring back to original shape when force lifted
Plastic: Ability to permanently change shape or deform when forced
o Ductile = very plastic, Brittle = not very plastic, fractures instead of bending.
Explain how gravity affects motion and energy, list the 5 types of energy, and describe what causes them to vary.
Force (F) A push/pull
Unit: Newton = 1 (kg * m/s^2) -> F = ma
A 15 km/h breeze = 1 N
Gravity (g) Force that 2ttracts matter
G = 9.8 m/s = gravitational acceleration
Types of Energy
Work (W) Work = force x distance in = Joules
Potential Energy Mass * gravity * height (distance against pull of gravity)
Kinetic Energy 0.5 m V 2
Sensible Heat (QH) Heat we can feel
ΔQ H m C ΔT
o C = specific heat capacity Latent Heat (Q E When solids melt/liquids evaporate – sensible heat becomes stored as latent heat
o When they condense/freeze - > released
Q = LΔm
Delta m = change in mass
o Latent Heat of Vaporization: liquid -> gas,vL
o Latent heat of fusion: liquid -> solidf L
Explain the 5 main concepts for understanding natural processes as hazards.
1. Hazards can be predicted through scientific analysis
Scientific method used
Identifying location, finding probability, looking for precursor events, forecasting, warning
2. Risk analysis is an important element in understand the effects of hazards
Risk = probability * consequences
3. Linkages among different hazards exist
4. Damage from natural disasters is increasing
6. Damage and loss of life can be minimized
Explain (with examples) how energy conservation applies to natural disasters.
o Energy is conserved when it changes form.
o Most sources of energy are diffuse: weak, but cover a wide area
o Disasters generally have a concentration of energy into a small area
Describe relationships between force, pressure, stress, strain, energy, and power.
Power: work/consuming energy per second = measured in watts
o Pressure: force per unit surface area applied perpendicular to a surface
o Stress: force per unit area applied parallel to a surface
Stress tends to strain deform objects
Describe population growth and explain why it is important for natural disasters.
o Population growth was exponential over the past 12,000 years
Doubling time = 70/growth rate
Applies only to an exponentially growing pop
o Carrying capacity + overpopulation limit the growth
Recent growth is linear -> growth limited?
o With greater population = infrastructure is more important + sensitive
Transport, communication, utilities etc
Harder to evacuate + communicate if damaged by disaster Unit 2: Earthquakes
Describe the global distribution of earthquakes and how often quakes of various magnitudes occur
o Earthquakes tend to happen near plate boundaries
Plate = lithosphere = crust + top of upper mantle. Strong layer, about 100 km thick.
Plates float on the asthenosphere
Oceanic plates: fast moving (cm’s/year), young (less than 200 MY), created at mid-ocean
ridges, destroyed at subduction zones
Continental plates: old (buoyant, not subducted), slower moving (mm to cm)
Relative motion of these plates results in…
Mid-ocean ridge spreading center: tension
Transform fault: shearing , slide past
Collision boundaries/subduction zones: compression
Understand the different types of faulting at different plate boundaries, and which plate boundaries produce the
1. Divergent plate boundaries: Plates move apart due to tension (stretching), small-ish earthquakes
2. Convergent plate boundaries: Due to compressive forces
Continental collision: Continental plates collide, tends to form mountains
Oceanic + continental: oceanic plate is subducted under continental -> volcanic activity
Oceanic + oceanic: once plate subducted under another
Convergent boundaries cause small to very large quakes.
Subduction zones cause the greatest quakes – located in Japan, Mexico, Alaska, etc
3. Transform plate boundaries: Plates move sideways past eachother, leads to shearing motion
Many moderate to large quakes, but not as large as
San Andreas fault, Queen Charlotte fault
4. Intraplate earthquakes: not at plate boundaries, can be
Occur along ancient fault lines/plate boundaries
which have been reactivated
Waves can travel far without getting smaller.
Many found in Ontario and Quebec.
Plate Boundaries near UBC
1. Queen Charlotte fault – north, near Vancouver island
2. Cascadia subduction zone: Juan de Fuca plate and North American plate
Divergent margin formed between Juan de Fuca and Pacific Plate
3. San Andreas fault much further, south.
Fastest plate on earth = Nazca plate
1. Creates mostly shallow quakes, biggest magnitudes are deep
In BC, most earthquakes (minor) happen around Vancouver and Queen Charlotte Islands. Some intraplates near
Quakes follow factor of 10 rule -> minor ones common, occur 10 times as less for every increase in magnitude Describe how the Earth builds, stores, and releases energy in earthquakes (elastic rebound)
o Types of stress: compressional, tensional, shear = depends on direction of force and orientation of surface
Pressure: compressional stress that is the same in all directions (Cup example). NOT STRAIN.
Changes an object’s volume, not its shape
Stress can involve forces with different magnitudes -> changes shape. Force per area.
Change of shape under stress = strain
Understand concepts of (1) stress causing strain and (2) plastic versus brittle deformation
o Responses to stress
Elastic deformation: relatively small stress, smalls trains but not permanent since material bounces
back. Energy can pass as waves.
Plastic deformation: like putty, material strains but does not bounce back
Brittle deformation: material stores elastic energy but will eventually break. Catastrophic release.
o Cold rock is brittle = upper crust. Can break if stress is large.
o Hot rock is ductile = most of Earth’s interior
Elastic Rebound Theory
o A pre-existing fault is locked by friction
BUT, elastic plates (“block”) on each side move slowly relative to each other (mm to cm per year)
This leads to the deformation of the blocks
Since they are elastic, shear stress gradually builds
Earthquake starts at hypocenter/focus. At
this points, two blocks slide past
In most cases, sliding stops and earthquake is
Rupture occurs when elastic stresses
However, in a large quake, a large part of the fault breaks and the blocks move relative to
each other. Elastic strain and shear stress decrease.
o At a depth, fault zones are ductile and not brittle. Relative motion of plates here is steady, so no quakes.
Describe how the rupture propagates from the focus and why shaking and damage are not necessarily greatest at
Faults are weak surfaces, weaker than surrounding rock
o They break repeatedly and may accumulate 100s of km of “slip” over millions of years
o Rupture begins at hypocenter and travels two ways
Maximum slip is usually NOT at the hypocenter
The rupture propagates away at 2-3 km/sec
Shaking is greatest in the direction the rupture travels!
Foreshocks sometimes formed, aftershocks always, aftershocks decrease as 1/time
o Biggest is usually 1 magnitude smaller than mainshock, however, distribution of SIZE does not vary
o Aftershocks form because earthquake stress changes can affect probability on nearby faults Describe the different types of seismic waves and how they move through the Earth
o When elastic energy of rocks is released, energy goes to breaking rocks, generating heat
o A tiny fraction of total energy causes seismic waves which can travel far from the hypocenter
Body waves: travel inside the Earth
o P wave (Primary)
Compression and extension of a solid – like a sound wave.
Fastest type of seismic wave, about 6 km/s in continental crust.
o S wave (Secondary)
Shearing distortion of the solid
Particle moves perpendicular to direction that the wave propagates
Slower than P wave, about 3.5 km/s. Cannot pass through fluids.
Surface waves: require an interface – ground-air, water-air, mantle-liquid outer core…
o Slower than body waves
o Rayleigh wave: vertical and horizontal motion parallel to wave direction like a rolling ocean wave
o Love wave: Horizontal movement, perpendicular to wave travel direction. Like a snake.
Understand the principle behind early warning systems (such as the one in Japan) and how much warning time
they can give
o Recording seismic waves at the earth’s surface allows us to locate earthquakes, find their magnitude and
maybe provide early warning.
Can tell us about earth’s interior: where are interfaces btw different materials, which parts are
Japan: The alarm goes out when P-waves are detected by seismometers near the epicenter. Warning time =
difference between P and S wave arrival times (seconds to minutes).
Describe how an earthquake is recorded and how to locate the epicenter
o Seismographs: heavy mass suspended by a spring. Seismograph moves with ground but the mass stays put -
relative motion causes pen to trace ground displacement over time.
o Geophones similar: use a magnet instead of mass, generates current when ground moves. Records velocity
vs time, but can be converted to displacement vs time.
Best = broadband seismometer, but $$$
o Waves contain many different frequencies jumped together, but one can be dominant
o Analyzing S and P llag time tells us distance to quake since P wave arrives first
o Can find distance to earthquake using 3 seismometers
Calculate distance D to quake at 3 different seismographs
Draw a circle of radius D
EPICENTER IS WHERE THE 3 INTERSECT
Global Seismic Network: detects M4+ events worldwide. 150 stations. Also detects nukes.
Local: Canadian National Seismograph Network – detects small quakes in lower mainland. ~1600 per year
Understand how local ground conditions can affect the duration and amplitude of shaking
o Earthquakes don’t kill. Collapsing buildings do.
Compare and contrast the meanings and uses of earthquake magnitude and intensity scales
o Magnitude: how much energy was released
o Intensity: how strong ground motion was felt at a location
A bulb has fixed magnitude, but different intensities depending on where you are. Explain the different magnitude scales, which one is best for large quakes, and why
Must be estimated indirectly since we can’t monitor the focus.
o Use seismic amplitude + distance to focus
o Can look at Richter (local) magnitude, surface wave magnitude, body wave magnitude or find energy
released and convert (moment mag)
Richter Magnitude M L
o Based on largest amplitude of shaking for high-frequency body waves (1 hz)
Energy increases 32 fold
Shaking increases 10 fold
Calculated using biggest amplitude and S-P lag time
Problem: most shaking from quakes is low frequency, as a result, Richter underestimates
o Moment magnitude M is most common for large quakes
Explain factors that determine earthquake intensity
o Distant quakes: small amplitude, lower frequency recorded
o Large: all frequencies
Close earthquakes feel like a jolt, far ones feel like a rolling
o Larger quakes: shaking amplitude is greater, shaking lasts longer, dominant frequencies are lower.
o Intensity is measured using Modified Mercalli index or instrumentally
Rated from I to XII (1 to 12)
Factor 1: Magnitude
o Maximum intensity correlates with magnitude but
o Smaller earthquakes can be devastating due to bad construction + after effects (landslides, fires etc)
Factor 2: Ground type
o Hard rocks do not amplify – mixture of frequencies
o Soft rocks amplify shaking – low-frequency waves may reverberate in basins
High frequencies absorbed
o Hard rock = north van, soft rock = Richmond. Waves trapped + amplify
Factor 3: distance from epicenter
o Large quakes produce low frequency shaking -> shakes tall buildings
o Small quakes produce more high frequencies -> small buildings shake
Different heights -> buildings can move and crash
Soft story buildings can collapse
Improperly reinforced concrete also collapses
Be aware of how earthquakes can be the cause of other natural disasters (e.g., tsunamis, liquefaction, landslides)
Soil grains may be loosely packed and saturated.
Ground motion can increase pore ﬂuid pressure.
Soil temporarily loses strength and ﬂows like a liquid.
Understand the basics of how buildings can be designed or retrofitted to better resist earthquakes (and reduce
o Base isolation: allow the ground to move under the building with isolators
o Dampers: absorb energy from the building fame transmitted from moving ground.
o Moment resisting frame of beams and columns with strengthened connections allows building to move and
evenly distributes load
o Retrofitting: fixing old buildings Add sheer walls, base isolators, dampers, reinforce walls, etc
Connecting a building to foundation is important
Identify fault zones that could produce an earthquake damaging to Vancouver.
o Queen Charlotte: M8
o Cascadia: M9?
Elastic stresses gradually building up as crust is strained (compressed). Causes uplift, can be
o Shallow crustal faults: big one will happen later
o Conventional forecast: based on recurrence interval. CONSTANT LINE.
However, over time elastic stress builds up. Chance of stress exceeding friction builds too.
o Renewal forecasts show increasing probability . We have these for Cascadia.
Recurrence time + standard deviation estimates required.
o Big quakes can trigger other quakes, so earthquake Interaction can be included. Rises temporarily. Unit 3: Landslides
Explain how the impact of landslides depends on 1) population density, 2) economic infrastructure, and 3)
o As population density increases, increasing damage.
o Most fatalities from a slides are under-reported as they accompany major disasters
Japan has the most deaths from landslides per year, but highest pop density as well
o Largest landslides in Canada happen on West coast (here), between BC and Alberta and in Quebec + Ontario
Explain why British Columbia has the highest frequency of landslides in Canada and what we should expect as our
population expands into the mountains.
o Mountainous terrain, lots of rain, complex geology (unconsolidated glacial sediments) and many possible
South BC: return period is 25 – 70 years for large slides
Distinguish between the 3 main failure modes (falls, flows, and slides) and how they are influenced by geology.
o Falls: very fast.
Occur on very steep slopes (usually rock)
Material detaches because of weakness – falls very fast due to gravity
o Slides – cohesive block moves on a surface
Vary from slow to fast. Usually soil, rock or debris
Curved/bowl shaped surface: Rotational slide (slump)
Usually weak material (sediment). Characterized by scarp above slide.
Flat/planar surface: Translational slide
Usually strong material. Cohesive block slides down.
o Flows – fluid motion (Chaotic)
Very fast – mudflows can be up to 80 km/h
Soil, mud, wet debris, rock. Water usually involved
o Complex movements (combination of above)
Categorize, identify, and name a variety of different landslides
o Landslides classified mainly by type of material and type of movement. Rate of movement also important.
Materials: Rock, Soil/Earth, Mud, Debris
Define Angle of repose
o Steepest angle a slope can maintain without collapsing. Depends on material.
Assess the balance between the strength of the slope and the destabilizing forces acting on it (Factor of Safety)
o Stability of a slope depends on
Driving forces: Gravity
Gravity is manifested as Shear stress “T”
Gravity force is parallel to the slope, moving downwards
Resisting forces (Shear strength) – “f”
Friction – resistance to sliding
Cohesion – material holding together
Normal stress – perpendicular to slope
o Factor of Safety (Fs) = (Tf/T) = (Shear strength / Shear Stress) = (Strength / Stress)
FS >> 1, stable slope
FS < 1, unstable – failure may occur
At angle of repose, FoS = 1 or just above. Compare and contrast landslide causes and landslide triggers.
o Causes – usually long term factors that lead to instability of slope
Reduce shear strength of a slope
o Triggers – translate instability into motion. Usually short term events.
o There can be many causes, but only one trigger.
List and describe several external causes of landslides
o Factors outside of slope that affect stability
o High slope angle
o Undercutting of a slope (removal of bottom) by roads, rivers, buildings
o Overloading a slope with excess weight
o Vegetation is weird…
Roots bind loose materials = good
Overloading by tress = bad
Avg temp and rainfall high = more water = increased weathering
Around 0 = frost wedging
List and describe several internal causes of landslides
o Water content
Present in all slopes. Adds weight (overloading)
Decreases normal foce/normal stress, which creases Tf
Medium for flows
In sediment (lose rocks, sand, silt), water can help or hinder cohesion depending on amount
No water = low angle of repose. Some water = high angle. Too much very low angle
In solid rock, reduces shear strength along planes of weakness and causes frost wedging
o Inherently weak materials - silt, sand, clay
Clay is so small that Van Der Walls force has an effect
When deposited in salt water, clay is attracted to other clay particles.
However, when salt content is lowered by percolating groundwater, “house of cards”
structure is broken and quake clay slide can occur.
o Adverse geological tructures can occur as well
Unfortunate bedding or fractures.
List several landslide triggers
o Earthquakes, snowmelt, rain, loud noises, jumping up and down, skiing, excavation, etc.
Compare and contrast several key triggers and causes of landslides and how they affect the force balance
equation (i.e. Factor of Safety)
Explain how liquefaction landslides develop in sensitive marine clays
List and describe the site conditions (Causes and Trigger) that lead to the development of the Rissa quick clay slide
o Melting water from glaciers caused clay deposits. Following withdrawal of glaciers, marine clay deposits
rose. Some of the best farm land in Norway.
Rain + surface water erode clay and upward flow of fresh ground water leaches salt out of water
Slide initiated by overloading.
Quick clay was liquefied.
Relate the type of landslide damage expected as a function of its velocity.
o Faster - > stronger. Identify tell-tale signs of an unstable slope.
Compare and contrast avoidance, prevention, and protection strategies for dealing with landslide hazards.
List the mitigation techniques commonly used for avoidance, prevention and protection strategies.
o Once we identify a hazard, we move on to trying to mitigate it.
o Start with investigating: will the slope fail or not? If so, where will it go?
Geological mapping, frequency + magnitude relationship.
Avoidance: move to a different area and avoid the problem
o Can map hazards and move things out of the away. Can also use modeling
o Can remove material – very simple. However, very expensive.
o Can add anchors – increase resisting forces by tightening cables.
o Drainage – remove water
o Add material at bottom of slope increases resisting forces.
o Add barriers / netting to control rock falls
o Debris flow protection: separate water and debris by removing debris (barriers)
o Prevent more debris from being added – concrete lined channel
o Slow down debris flow and reduce erosive capabilities – boulder embedded channel
Identify the appropriate mitigation strategy for a variety of risk situations.
Unit 4: Volcanoes
Explain what magma density and magma viscosity are
o Magma: mixture of molten rock, crystals and gas below the earth’s surface
o Created by the melting of pre-existing rock in Earth’s interior (mantle + crust).
Reaches the surface through fractures, erupts as lava or pyroclastic material (tephra)
o In order for magma to rise, it must be
List the different categories of volcanic rocks and Less dense than crust
Runny enough to flow
Hot enough to stay liquid
o Main gases: H2O< Co2, SO2, Cl2
At a depth, <10% gas content. This decreases viscosity and density
As pressure decreases, the gases become less soluble and bubbles form
o Viscosity = runninses, resistance to flow.
Explain the differences between the magmas they came from
Igneous rocks come from solidifying magma
Mafic Rock Felsic Rock
Rich in denser minerals (olivine, pyroxene), darker in Rich in low density minerals (quartz, feldspar) ls, light
Mafic rocks Felsic rocks
Basalt (extrusive), Gabbro (intrusive) Rhyolite (extrusive), Granite (intrusive)
Dacite (extrusive), Tonalite (intrusive)
Big crystals = intrusive aka plutonic (Granite, Gabbro). Small crystals = extrusive
Freezes in crust, never erupted. Cools slowly. Rapidly cooled Intermediate rocks:
Dacite (ext), Tonalite (int)
Andesite (ext), Diorite (int)
Explain why some magmas erupt explosively (as pyroclastic material) and some magmas erupt effusively (as lava)
Basalt Andesite Dacite Rhyolite
Mafic (less silica) Felsic (more silica)
Hot (1200-1400 C) Intermediate Cool (600-1000 C)
Low viscosity (RUNNY