Lectures 1 - 10 Flashcards
define natural disaster
large amount of energy released in a short time, with consequences for life and infrastructure
give a example of a natural hazard
unstable rock on mountain slope
spring and fall there are heavy rains. give the frequency and return period of heavy rains a year
frequency = 2 per year
return period = 1 every 6 months
give the 4 sources of energy
earth’s internal energy,
solar energy,
gravity,
impact energy,
list the 4 global trends
–disasters are increasing over time
–fatalities are increasing over time
–human made disasters been decreasing
– economic loss is increasing
list the 3 Canadian trends
–natural disasters increasing with time
–fatalities are decreasing
–economic losses are due to weather-related disasters
define risk
risk = vulnerability * Hazard
what are the 4 pillars of emergency management
–Response
–Recovery
–Mitigation
–prepardness
what is the term for : “middle-term activites to put the situation back to normal”
recovery
what is mitigation
Long term actions to eliminate risk… addresses the root cause of the problem
define preparedness
planning for disasters by putting in place resources to cope with the problem when it occurs
define adaptation
gradual adjustments to reduce harm
who is the father of plate tectonics
J. Tuzo Wilson
how does the solar nebula constrain planets?
make planets move in the same direction as the disk
orbits on the same plane
what is differentiation?
a process by which gravity causes denser material to gradually migrate to the center of the planet
list the elements that make up the following Crust, Mantle, Outer core, Inner Core
Crust : silicon and oxygen
Mantle: Iron and magnesium
Outer core: Liquid Iron
Inner core: solid Iron
what is the difference between oceanic crust and continental crust?
oceanic = more dense, and thin
continental = less dense, and thick
what are the strength of the following layers?
lithosphere
asthenosphere
mesophere
lithosphere = Rigid asthenosphere = soft plastic mesophere = stiff plastic
what layer are tectonic plates
lithosphereic floating on asthenosphere
whats the lithosphere/asthenosphere depth boundary
100km
how do tectonic plates move?
they move due to convection cells
how long is a tectonic cycle?
250 Ma
what is subduction
process in which a lithospheric plate descends beneath another
what is bathymetry
depth measurements at various places in water
where do shallow earthquakes happen
overriding and subducting plate.
deep earthquakes in subducting plate only
what dominant force is at divergent zone?
tension
what dominant force is at convergent zone
compression
what dominant is at transform fault
shear
where do 80% of earthquakes and 75% of active volcanoes lie?
pacific plate
where is Ottawa location
center of North American plate
at what depth do hypocenters stop?
700 km because material in mesosphere is soft
list for the 4 steps to a new oceanic lithosphere
Centering: lithosphere centers over hot region
doming: lithosphere bulge up into a dome
rifting: area is pulled-apart by tension
spreading: new lithosphere is formed in pulled-apart area
what types of earthquakes are at the subduction zone ~30 km
Megathrust - due to shear stress
crustal earthquakes - due to compression
what types of earthquakes are at the subduction zone > 100 km
intra-slab earthquake, due to cold rock being consumed into hot asthenosphere
what are the two plates involved with the Cascadia megathrust
North American plate (overriding)
Juan de fuca plate (subducting)
which type of faults cause infrequent, major, shallow earthquake
transform faults (shear force)
what is a fault
fracture across which two blocks move relative to each other
positive or negative correlation between rupture length and magnitude
positive
define the following:
- -seismometer
- -seismograph
- -seismogram
seismometer – sensor that detects ground motion
seismograph – instrument that records ground motions
seismogram – paper record or digital file with data describing ground motions
what are the frequency of body waves? of surface waves?
body > 1 hz
surface < 1 hz
what is the sideways motion from?
S waves (shear energy)
define intensity
measure of the effects of an earthquake on people and infrastructure
what does Mercalli intensity scale measure
eye witness accounts,
damage to infrastructure
generated automatically in real time.
shakemap
what is a Felt area
area of the perceptible earthquake ground motion
is size of the felt area a good indicator of magnitude?
NOPE
what are the depths of megathrust earthquake hypocenter?
Shallow (~30km)
how can you tell if a earthquake is a aftershock or a new earthquake?
mainshocks and aftershock have the same hypocenter
the top ? Meters of rocks and soils have a major impact of ground motion
30
what is natural frequency of soils? hard rocks?
soils < 1 Hz
hard rock > 1 Hz
what is resonance?
system experiences very large oscillations when disturbed by a force function of frequency equal to its natural frequency
whats the Hz of body waves? Surface waves?
body waves > 1 Hz = hard rock
surface waves < 1 Hz = soils
where does liquefaction occur?
saturated soils, where space between particles are filled with water.
whats better for earthquakes wood or masonry and why?
wood, cause higher elastic limit
how do you calculate natural frequency
10 hz / number of stories
what can we predict about earthquakes
- -how much ground shaking there will be
- -where earthquakes are likely to occur
what magnitude of earthquakes cause a Tsunami
7.5
what causes a tsunami
vertical motion of rocks
when does shoaling occur
hen depth < WaveLenght / 2
how many meters water of wavelengths are wind caused waves confined to
first 100 meters
how long are Tsunami waves
~100 km, always interacting with the sea floor
what caused the indian ocean tsunami to be so destructive
lack of awareness also was caused by a megathrust earthquake. with a vertical slip of 10 m
what caused the Japan earthquake and tsunami to be deadly?
height of waves underestimated
what earthquake triggered a tsunami by landslide?
grand banks earthquake
where are hazards the highest in canada?
BC due to earthquakes
which rocks form by cooling and solidfication from hot molten rock material
igneous
whats the difference intrusive and extrusive igneous rocks
- intrusive: (cooling at depth) slow, large grains
- extrusive: (cooling at surface)
fast cooling, small grains
igneous cooling: pale rocks mean ?
high SiO2 content (above 65)`
what are the 3 factors that control viscosity?
1) SiO2 (higher Si02 content higher viscosity)
2) temperature (lower temp higher viscosity)
3) # of solids (more solids, higher viscosity)
give an example of low viscosity magma
basltic
give an example of high viscosity magma
rhyolitic
whats the main volatile from a volcano
H20
give the measurements of
Ash,
Lapilli,
Scoria,
Ash < 2mm
Lapilli 2-64 mm
Scoria > 64 mm
what are the difference between bombs and blocks?
bombs: are semi-molten fragments when airborne.
blocks: are ejected as solid fragments
what are the four tectonic environments
`1) divergent zone
2) convergent zone
a) subduction zone
b) continent-continent collision zone
3) transform fault
4) hotspot
what are the four tectonic environments with volcanic activity
1) divergent zone
2) convergent zone
a) subduction zone
3) hot spot
in general list whether the following are peaceful, explosive or both.
- divergent zones
- subduction zones
- hot spots
- divergent zones = peaceful
- subduction zones = explosive
- hot spots = both
what is the role of water for volcanoes at subduction zones?
water lowers the melting point of rock and allows magma to rise through overriding plate
what provides more SiO2 enrichment? Oceanic-Continental or Oceanic-Oceanic
Oceanic-Continental
how are hotspots aligned? can call the age of a hot spot?
with the direction of plate motion.. age increases with distance of hot spot
hotspots, if rising magma mixes with thick continental crust it will be what type of explosion? thin
thick crust = explosive
thin crust = peaceful
list the steps of a volcanic eruption
1) solid rock rises closer to surface (due to convection loop) this causes decompression melting
2) more rocks liquify causing volume expansion
3) gas (volatiles) come out of melt
4) when bubbles reach >= 75% of magma volume gas jet expels magma in atmosphere
what are the three Vs of volcanism
1) Viscosity
2) Volatiles
3) Volume of magma
describe the 3 Vs of icelandic-type eruptions and what landform does it create?
Viscosity = Low
Volatile Content = easily escaped
Volume = small
lava plateau
what tectonic environments do you find: hawaiian-type eruptions and Icelandic-type eruptions
Divergent zones and Hot spots
what are the 3 Vs of Hawaiian-type eruptions? and what landform does it create?
Viscosity = Low
Volatile content = Low
Volume = Large
Shield volcano
whats the difference between a lava plateau and shield volcano?
shield volcano is larger,
shield volcano is a shape of a dome while lava plateau is flat.
shield volcano has a Surface rupture
what are the 3 Vs of Strombolian-type eruptions?
and the landform it creates
Viscosity = medium
Volatile content = medium
Volume = small
Scora cone
Scoria ccone is typically a monogenetic volcano. what does this mean
its eruptive phase is a few years.. and it doesn’t erupt again
what are the 3 Vs of a Vulcanian-type eruption? and the landform it creates
Viscosity = medium
Volatile content = Medium
Volume = Large
stratovolcano
what do Plinian-type eruptions normally follow?
Vulcanian-type
whats the main difference between Philnian-type and Vulcanian-type eruptions
height of eruption
During main phase what re the 3 Vs of Philnian-type eruptions
Viscosity = Medium
Volatile Content = High
Volume = Large
During final phase what re the 3 Vs of Philnian-type eruptions
and what is the landform?
Viscosity = High
Volatile content = Low
Volume = Small
lava dome
what are the details of a lavadom
volcanic cone with a highly viscous blob of lava forming over a half-ball over the vent
what are the 3 Vs of a ERTH2415
Eruptive style and landforms Caldera-type eruption?
Viscosity = High Volatile = High Volume = High
what type of eruptions are the largest?
Caldera-type eruption
list the steps of a typical explosive eruptive sequence.
early phase: vulcanian-type eruption thus formation of a stratovolcano
major phase: Plinian-type eurption, continued development of a stratovolcano
final phase: Plinian-type eruption (lava dome) OR caldera type eruption (caldera)
what are Canadian volcanoes associated with?
curstal rifting
what is responsible for the largest number of fatalities related to volcanism
Pyroclastic flow (hot gases and ash and rock moving down volcano)
what is Lahar
mudflow that originates on the slopes of volcanoes when volcanic ash and debries become saturated with water
where does lahar occur
almost always on stratovolcanoes
why is mitigation hard for volcaones?
low frequency, high magnitude
difficult to predict
what are the three factors of the VEI
volume of material extruded
height of eruption
duration of eruption
