Tectonics 2 Flashcards
Diverge = decrease overlying pressure, converge = high pressure, all boundaries = friction, gases build up = pressure
How does Cross-Bracing help infrastructure be more earthquake-resistant?
- use two steel beams, reinforce walls
Define earthquake
Shaking of earth’s ground
sudden release energy (litosphere)
only involves fully solid litosphere along fault lines
Where do earthquakes generally occur at?
Along plate boundaries which have a system of faults
All plate boundaries have faults.
How does earthquakes form? (4 points)
- Rock masses, either side of fault pushed by [tectonic force]
- Friction causes plates get locked, stress builds up
- When stress exceeds strength of [rock/ fault], rocks [snap/suddenly move to] another position
- causes seismic waves release, result in ground shaking
https://docs.google.com/document/d/12rAwkWXiw5RGFDGpRY3RhY_ab2Cs2ZpI7u36Bog2OvM/edit?tab=t.0
page 3
What are faults?
A system of deep fractures
What is a focus?
the place inside Earth’s crust where earthquake originates
where is the origin of an earthquake?
focus
what is the epicenter?
the point on earth’s surface directly above focus
where is shaking most strongly felt?
near the epicenter
how are earthquakes measured?
seisometers
how do the equipment to measure earthquake work?
sensitive instruments detect ground vibration, determine magnitude
Increasing what will incrase the magnitude of earthquake?
Seismic energy
released
Which scales do scientists use to rate magnitude of earthquake?
- ML (richter scale)
- Mw (Moment magnitude Scale)
How does Richter Scale place earthquakes on the scale?
- largest wave height recorded (seismometer)
- based: maximum seismic intensity
Richter Scale’s characteristics
- Numbered from 1-10
- Logarithmic
Logarithmic scale seismic energy scaling
32x more energy
LINK
- Mw Scale: Moment Magnitude Scale
- ML Scale: Richter Scale
What are the limitations of Richter Scale?
underestimates longer earthquakes release more overall energy
e.g.; rate earthquake w/ 1 single drastic spike vs earthquake w/ many large waves as higher
Is the richter scale commonly used?
No
- small, local earthquakes only
How does the Moment Magnitude Scale rate earthquakes?
- total energy released during earthquake
- estimates total energy released
Which scale is more accurate? Richter or Moment Magnitude?
Moment Magnitude (Mw) generally more accurate
Characteristics of Mw Scale
- Logarithmic
Increase in 1 = 10x more powerful But 32x more seismic energy released
Example of earthquake adjust Richter -> Mw
1964 Prince William Sound Earthquake
- Readjust Richter 8.6 -> Mw 9.2 (more accurate)
What is magnitude?
Measuring amount of seismic energy
How are volcanoes created?
When lava erupts onto Earth’s surface cools, forming cone-shaped mountain
(By God, btw!)
Which plate boundaries do volcanic eruptions occur?
- Divergent
- Convergent
Only at these boundaries do volcanoes form
How does volcano form at divergent plate boundaries?
5 parts
- Plates diverge
- Crust stretches, fractures develop
- Decreased overlying pressure causes underlying mantle, melt -> magma -> rises in weak areas of crust
- erupts as lava (volcanic eruption)
- cools, solidifies, accumulates over time, form volcano
Lava is magma on the surface
By God.
How does volcanoes form in o-c, o-o convergent plate boundaries?
7 parts
- Plates converge
- Denser plate subducts under less dense plate
- High pressure forces water out of O crust
- Water lowers melting pt of overlying mantle, causing it to melt -> magma
- Magma contains dissolved gases, less dense than surrounding materials, hence rises thru weak areas in crust
- Erupts as lava (volcanic eruption)
- lava cools, solidifies, accumulates over time, forms volcanoes
c-c convergence has no volcanoes forming
both conv, div, talking about overlying
4 steps
How does High Silica Magma cause a violent, explosive explosion?
- More viscous
- As magma rises -> surface, dissolved gases in magma difficult escape
- More pressure builds up
- gases escape explosively
Is high silica magma in stratovolcanoes or shield volcanoes?
BOTH
- More associated with stratovolcanoes
How does low silica magma lead to gentle, e___ explosions?
- Less viscous magma
- Magma rises to surface -> dissolved gases escape easily
- Less pressure builds up -> gentle, effusive explosions
What is viscous?
Thick, sticky consistency
Just imagine the thick, sticky magma. Gases would obviously find it harder to escape through thicker and sticker magma
what is effusive eruption characterized by? (4)
- gentle
- mainly lava outpouring into ground
- no tephra ejected
- non-explosive
Is low silica magma in stratovolcanoes or shield volcanoes?
BOTH
- More associated with shield volcanoes
Shield = defensive
Therefore strato = offensive
“Defensive Volcano” will eject a gentler, effusive eruption
How do stratovolcanoes form? (4 points)
- High viscosity magma, rises thru weak areas in crust -> Earth’s surface, erupts explosively as lava, ash, rocks
- Ash, rocks settle on sides of volcano, later covered by layer, lava
- After successive eruptions, tall volcano consist of alternating lava, ash layer develop
- Highly viscous lava travels shorter distance before cools, solidifies -> volcano has steep sides, narrow summit
o3o pattern does not equal to made smhh
How does shield volcanoes form?
- Low viscosity magma rises thru weak areas in crust -> Earth’s surface, erupts effusively
- After successive eruptions, volcano consisting of layers of lava develops
- Less viscous lava travels longer distance before cools, solidifies, volcano has gently sloping sides, broad summit
How is volcano intensity measured?
Volcanic Explosivity Index scale
What does VEI scale base itself on?
- Vol. of ejected material
- Height of eruption cloud
- Duration of eruption
VEI scale characteristics
- Measured on scale of 0-8
- Effusive eruptions given value of 0-1
- 8 = supervolcano
- Logarithmic scale
Increase in 1 = 10x more powerful
Numbers! Numbers! Numbers!
Amount of material ejected from effusive eruption VS mega-colossal explosive eruption tephra and eruption cloud
effusive
- <0.0001km^3 material
mega-colossal (VEI > 8 supervolcano)
- >1000km^3 tephra
- >25km eruption cloud column
What is tephra
- any type/size rock fragment
- forcefully ejected
- travel airborne path (during eruption)
What is volcanic cone
triangle-shaped hill/mountain formed as lava accumulates around vent
What is magma chamber
Location in Earth’s crust where magma located
what is crater
Bowl-shaped depression at top of volcano
what is lava
molten rocks erupted onto Earth’s surface
what is conduit?
central passageway in volcano which magma travels through
3 statuses of volcano
- active (erupt recently, likely erupt again)
- dormant (erupt in last 2000 yrs)
- extinct (no evidence of eruption in historic times, no evidence of magma reservior
what is magma
molten rocks found below Earth’s surface
what is active vent
- opening, Earth’s surface through which lava erupts,
- at bottom, crater
https://docs.google.com/document/d/12rAwkWXiw5RGFDGpRY3RhY_ab2Cs2ZpI7u36Bog2OvM/edit?tab=t.0 page 3
What boundaries do earthquakes occur along? How does earthquakes occur at plate boundaries?
all
plates are pushed by tectonic forces -> stress builds up -> energy eventually released
do earthquakes only occur along plate boundaries?
List the rough quantity of earthquakes along 1 specific transform, convergent, and divergent boundary
no.
- Eurasian Plate
- Broad belt of earthquakes along convergent plate boundaries of PROF
- Narrow belt of earthquakes along divergent plate boundary of Mid-Alantic Ridge
- Narrow belt of earthquakes along transform plate boundary of San Andreas Fault
Give specific examples.
Where is the largest concentration of earthquakes in?
Pacific Ring of Fire
Which, out of the 3 plate boundaries do earthquakes occur more commonly in?
Convergent
More stress built up during subduction
What is the Pacific Ring of Fire?
Broad belt around Pacific Ocean where most earthquakes, active volcanoes occur
Which plate boundaries does the Pacific Ring of Fire contain?
- Convergent: Pacific + Phillippine
- Divergent: Pacific + Cocos
- Transform: Pacific + North American
refer to plate tectonic map for clearer view
Where are volcanoes generally found?
Example of quantity of volcanoes found in these boundaries
Convergent (except C-C) + divergent boundaries
Convergence
- Belt volcanoes along Pacific Ring, Fire’s convergent plate boundaries’ subduction zones
Divergence
- Belt volcanoes along divergent plate boundaries between NA, Eurasian Plates
Any volcanoes at transform plate boundary?
No
Magma does not rise -> Earth’s surface form volcanoes
What are hot spot volcanoes?
Volcanoes that develop over into hot regions in mantle
- May develop in locations away from plate boundaries
General hazards of earthquakes
- Ground shaking
- Soil liquefaction
- Landslides
- Tsunamis
General hazards of volcanic eruption
- Tephra
- Volcanic gases
- Lava flows
- Pyroclastic flows
- Lahars
- Volcanic landslides
What is distribution?
Way that something is spread out/arranged over geographic area
What is a secondary cone? When does it form?
Small volcano formed on side of main volcano
- pressure builds up
What is soil liquefaction?
saturation, loose soil losing structure
transforms into thick fluid (due to ground shaking)
Which boundaries do strato and shield volcanoes mainly lie on?
Strato: Converging
Shield: Diverging
What is pyroclastic flow
**Hot clouds **of gas, ash, rocks
travel down slopes of volcano at >200km/h
Strato only
What is lahars?
Mudflows, comprising -> volcanic ash + water
What is tsunami?
Series of ocean waves
High silica magma = increased rate of flow.
Is this true?
no.
High silica = increased visocity = thicker = slower flow rate
Characteristics of earthquake hazards
- soil liquefaction, ground shaking, landslides usually localized, occur near plate boundary
- tsunamis (can travel thousands of kilometers from epicenter)
Characteristics of volcanic eruption
- volcanic gases, lava flows, pyroclastic flows, lahars, volcanic landslides localised
- Volcanic ash can travel thousands of kilometers
Can be Hotspot volcano therefore not alw near plate boundary unlike earthquake
Tephra is ambiguous as some is too heavy to travel far. some are quite small, can travel far
is ash always localised/spread away from the eruption?
no
dispersal of ash depends on
- wind conditions
- volume of ash erupted
- height of ash thrown into atmosphere
What is geothermal energy?
- energy derived from heat in Earth’s crust
we never even dig to mantle b4 lol
what is weathering
breaking down/dissolving of rocks on Earth’s surface
How does all earthquake/tsunami/volcano hazards affect natural and human systems? (4 points)
- Destroys ecosystems
- Destroys properties, infastructure
- Disrupts human systems
- Causes fatalities, injuries
tsunami isnt undersea earthquake. Not all of them are triggered by it
Not all have all four.
e.g. volcanic gses only has destroy ecosystem, properties, cause fatalities
How does ground shaking destroy ecosystems?
- ruptures chemical factories -> pollution
- fractures, uproot trees
how does ground shaking destroy properties and infastructure?
Weaken roads, buildings -> collapse -> difficult to rescue people/supply aid
How does ground shaking disrupt human services?
- snap waterpipes, result in water shortages
- snap communication+electricity cables, affect important comm. services
((Gas+Water Pipes Electricity+Communication Cables) e.g. snap waterpipes, result in water shortages)
How does ground shaking cause injuries and fatalities?
people trapped under collapsed infrastructure -> fatalities, injuries
how does soil liquefaction destroy natural systems?
- trees on liquefied soil sink, tip over, damage wildlife habitats, cause biodiversity loss
how does soil liquefaction destroy properties and infrastructure?
infrastructure sink into soil -> tip over -> make rescuing difficult
how does soil liquefaction disrupt human services?
roads and railways above liquefied soil sinks -> disrupt aid services
how does landslides destroy natural ecosystems
- fast-moving debris bury huge areas of forest, pollute rivers
- River blockages may cause floods
how does landslides destroy properties and infastructure
Debris bury villages, farms destroy infastructure
how does landslides disrupt human services
- Debris -> (same as groundshaking disrupt human services)
- roads, railways blocked by debris -> rescuing/aid more difficult
((Gas+Water Pipes Electricity+Communication Cables) e.g. snap waterpipes, result in water shortages)
Tip: think about what the debris/ground shaking/tsunami can snap (gas, water, electricity
how does landslides cause fatalities and injuries
- debris bury/hit people
- debris block rivers -> floods -> drown ppl
blocking rivers cause flood
flood cause
- drowning
- flood coastal areas e.g., kill wildlife
are tsunamis always caused by undersea earthquake
no.
- landslides can also cause it!
can tsunamis travel to the coastline?
yes!
Tsunamis can travel over thousands of km, devastate huge areas of coastline
4 parts: How do tsunami occur?
- Undersea earthquake causes seabed be displaced, large vol. of water lifted,
- form waves great wavelength, low height (<1m) travel -> land (high speed, >800km/h)
- approaching coast, greater friction w/ shallower seabed slows waves down
- onshore Waves get closer tgt -> increase in height (15m or more, 30-50km/h )
- Undersea
- At sea
- Approaching coast
- On coast
For tsunami, think about w___ and d____
how does tsunami destroy ecosystems?
- flood huge coastal areas, wetlands
- large amt. debris carried by waves pollute, kill wildlife
water and large amt of debris
when think about tsunami, w___ and d____
how does tsunami destroy properties and infastructure?
fast moving water, debris carried in waves -> sweep away infastructure
water and large amt of debris
how does tsunami disrupt human systems?
fast moving water, debris carried in waves
same as tsunami destroy properties, infastructure + Ground shaking human system impact
- water and large amt of debris
- snap (electricity, comm. cables)
electricity, gas, comm., water
how does tsunami cause injuries and fatalities?
- sweeping waters drown people
- large amts. debris carried in by waves hit, kill ppl
Tephra, think about a___, v___ b____
How does tephra destroy ecosystems
- ash carried thousands km away by prevailing winds, pollute huge areas o/ habitats, forests
- ash suffocate, kill wildlife
all about ash
Tephra think about v__b__ and a__
How does tephra destroy properties and infastructure?
- volcanic bombs hit properties, cause damage
- ashfall accumulate roof building + water -> double weight -> collapse
- ash corrodes buildings, weakens structure
- ash damage farmlands, suffocate livestock
ashfall is acidic due to acid-looking lava
how big are volcanic bombs?
- from few cm to as big as a car
tephra, think about a___ and v__b___
how does tephra disrupt human services?
- ash particles damage plane engines, disrupt air transportation
when think about tephra: a__, v__b__
how does tephra cause injuries and fatalities?
- volcanic bombs hit people, cause injuries, loss of lives
- ashfall cause respiratory, eye problems + suffocation
when think about volcanic gases, 2 gases: s__ d___ and c___ d___
how does volcanic gases destroy ecosystems?
- sulfur dioxide -> acid rain (react w/ water in air) damage trees
- cold carbon dioxide heavier than air, high conc. low-lying areas e.g. river valleys -> kill wildlife
high conc. in low lying areas as it sinks
btw Co2 still in gaseous form tho it is cold.
when think about volcanic gases, 2 gases: s__ d___ and c___ d___
how does volcanic gases cause fatalities?
- sulfur dioxide irritate Eye Nose Throat
- > 3% conc., carbon dioxide causes breathing difficulties, >15% conc. cause death
what gases does volcanic eruptions releaes
- sulfur dioxide
- carbon dioxide
are deaths caused by lava flow common?
no
- people easily move out of way
characteristics of lava flows
- extremely hot
- high/low silica
- travel over some distance from volcano
Lava is h___
how does lava flow destroy ecosystem
- hot, low-silica lava travel over some distance, destroy forest, habitats
Lava is h___
How does lava flow destroy properties and infastructure?
Burn through properties, infastructure
How does lava flow affect human services?
- (same as ground shaking destruction)
destroy: (water, gas pipes)
(electricity, comm. cables)
how do pyroclastic flow occur
- column of hot ash, gas gets thrown up into air by volcano
- falls back down to ground due to gravity
characteristics of pyroclastic flow
- > 200km/h speeds
- travel several kilometers, localised
700deg celc
most devastating
Pyroclastic VS volcanic gases
Pyroclastic
- damn fast (>200km/h)
- hottest
- gas, ash, rocks
volcanic gases
- sulfur, carbon dioxide
- acid rain (sulf. dioxide), suffocation (carb. dioxide)
- gases only
700 deg celc
think about t___, h___ f___, a__
how does pyroclastic flow destroy ecosystems?
thick layers ash cover path pyroclastic flows -> pollution of forests
huge areas forest destroyed, biodiversity loss ;D write this everytime for Ecosystem
ash, hot flows, temperatures
how does pyroclastic flow destroy properties and infastructure
burn through homes, infastructure
Displacement of people
need for Cause n Effect
how does pyroclastic flow disrupt human systems
- hot flows (same as how human systems are affected by ground shaking)
electricity, comm.
gas, water
how does pyroclastic flow cause injuries and fatalities
extreme temp. burn, kill people in fraction of sec.
how are lahars formed
huge amts. of ash+rocks ejected during eruption mixed w/ water
2 example scenarios where lahars are formed (not specific example)
- pyroclastic flows melt snow, ice, mix/w water on volcanic cone
- Intense rainfall wash down on ash
how does lahars destroy ecosystems
- cover forest, ecosystems with thick mud
- pollute rivers, kill aquatic life
how does lahars destroy properties and infrastructure?
Thick mudflows harden, concrete, burying properties
how does lahars disrupt human services
- roads railways blocked by thick mudflows
- lahars can (same as ground shaking affect human services)
lahars can damage comm. + electricity cables, water, gas pipes => disruption of comm + water shortage + disrupt supply of gas
how does lahars cause fatatlities?
- bury houses w/ residents, killing them
are volcanic landslides more common on strato or shield volcanoes? why?
strato
- strato taller, steeper volcanic cone, comprises of alternate layers of soldified lava layers + loose tephra
how does a volcanic eruption lead to a volcanic landslide
- blast, explosive eruption
- trigger downward movement of loose volcanic material
landslide think abt d__
how does volcanic landslide destroy ecosystems
- fast moving debris bury forests
- debris pollutes rivers, kill aquatic life
- debris blocks rivers -> floods -> damage nearby ecosystems
landslide think about d___
how does volcanic landslide destroy properties?
- debris bury villages, destroy properties
landslide think about d___
how does volcanic landslide disrupt human services
- debris block roads, railways -> difficult to rescue ppl/emergency aid
- debris (same as how landslides affect human systems)
debris snap electricity, comm. cables, water, gas pipes affecting supply of services, cut of comm.
landslide think about d___
how does volcanic landslide cause fatalities
- debris bury/hit people -> injuries
- debris block rivers -> cause flood -> drowning
4 main benefit of living near volcano
- Farming w/ fertile soil
- Extract precious materials, fossil fuel
- Harness geothermal energy
- Tourism
Why is the soil near volcanoes fertile?
- volcanic rocks undergo weathering -> fertile soils
think money, employment
why is the fertility of soil attractive to locals?
- soil suitable for agriculture -> higher crop yields
- locals earn more $$
How is precious materials and fossil fuels formed near volcano?
- magma cools, solidifies beneath volcanoes -> form precious materials
think reasons for money, employment
Why does precious materials attract communities to live near volcanoes? [3]
- Employment, mine, source of income
- Volcanic materials used for construction (i.e. sand)
- Govt. sell these minerals provide social services, locals
characteristics of a place that geothermal energy can be harnessed
harnessed in tectonically active areas such as volcanoes
why can geothermal energy be harnessed in volcanoes?
- derived from heat in Earth’s crust
- hot rocks under Earth’s surface heat up groundwater -> steam -> harnessed to generate electricity
tectonically active
think money, employment
why is geothermal energy in volcanoes attractive to locals?
- cheaper electricity produced locally
- employed in geothermal power plants
why are tourists interested in volcanoes as a tourist site?
- tectonic env. unique, attractive
- volcanic features appeal to tourists (e.g. crater)
- sightseeing, hiking
Link to Tourism:
Motivation to Travel -> Need for Unique travel experiences
It is a scenic spot, tourists are curious, it is something unique to say you have been near a volcano, so they go there
think money, employment
why does high tourism in volcanoes attract locals to live near it?
- provide local w/ employment opportunities (tour guides, accomodation, food providers)
- boosts local economic development
