tect 2 (undone!!) Flashcards
1
Q
Define earthquake
A
LINK
Litosphere: Uppermost mantle, Plate
Answer
- Shaking of earth’s ground due to sudden release of energy from litosphere
2
Q
Where do earthquakes generally occur at?
A
Along plate boundaries which have a system of faults
All plate boundaries have faults.
3
Q
How does earthquakes form? (4 points)
A
- Rock masses on either side of fault pushed by [tectonic force]
- Friction causes plates to 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
4
Q
What are faults?
A
A system of deep fractures
5
Q
What is a focus?
A
the place inside Earth’s crust where earthquake originates
6
Q
where is the origin of an earthquake?
A
focus
7
Q
what is the epicenter?
A
the point on earth’s surface directly above focus
8
Q
where is shaking most strongly felt?
A
near the epicenter
9
Q
how are earthquakes measured?
A
seisometers
10
Q
how do the equipment to measure earthquake work?
A
LINK
Seisometer
ANS
sensitive instruments detect ground vibrations, determine magnitude
11
Q
Increasing what will incrase the magnitude of earthquake?
A
Increasing the seismic energy released
LINK
Earthquake occur when seismic waves are released
12
Q
Which scales do scientists use to rate magnitude of earthquake?
A
- ML (richter scale)
- Mw (Moment magnitude Scale)
13
Q
How does Richter Scale calculate earthquake magnitude?
A
- height of largest wave recorded on seismometer
- based on maximum seismic intensity reached
14
Q
Richter Scale’s characteristics
A
- Numbered from 1-10
- Logarithmic
15
Q
What does a logarithmic scale mean?
A
Earthquake of Mw/ML 2 is 32 times greater than Mw/ML 1
LINK
- Mw Scale: Moment Magnitude Scale
- ML Scale: Richter Scale
16
Q
What are the limitations of Richter Scale?
A
- underestimates longer earthquakes that release more overall energy
- rate an earthquake with 1 single drastic spike larger than earthquake with many large waves as higher
17
Q
Is the richter scale commonly used?
A
No
- small, local earthquakes only
18
Q
How does the Moment Magnitude Scale rate earthquakes?
A
- total energy released during earthquake
- estimates total energy released
19
Q
Which scale is more accurate? Richter or Moment Magnitude?
A
Moment Magnitude (Mw) generally more accurate
20
Q
Characteristics of Mw Scale
A
- Logarithmic
21
Q
Example of Mw Scale being used
A
- Prince William Sound Earthquake readjusted from Richter scale to Mw Scale (more accurate)
22
Q
What is magnitude?
A
Measuring amount of seismic energy
23
Q
How are volcanoes created?
A
When lava erupts onto Earth’s surface cools, forming cone-shaped mountain
(By God, btw!)
24
Q
Which plate boundaries do volcanic eruptions occur?
A
- Divergent
- Convergent
Only at these boundaries do volcanoes form
25
How does volcano form at divergent plate boundaries?
5 parts
1. Plates diverge
2. Crust stretches, fractures develop
3. Decreased overlying pressure causes underlying mantle, melt -> magma -> rises in weak areas of crust
4. erupts as lava (**volcanic eruption**)
5. cools, solidifies, accumulates over time, form volcano
| Lava is magma on the surface
## Footnote
By God.
26
How does volcanoes form in o-c, o-o convergent plate boundaries?
7 parts
1. Plates converge
2. Denser plate subducts under less dense plate
3. High pressure forces water out of O crust
4. Water lowers melting pt of overlying mantle, causing it to melt -> magma
5. Magma contains dissolved gases, less dense than surrounding materials, hence rises thru weak areas in crust
6. Erupts as lava (**volcanic eruption**)
7. lava cools, solidifies, accumulates over time, forms volcanoes
| c-c convergence has no volcanoes forming
27
# 4 characteristics
How does High Silica Magma cause a violent, explosive explosion?
1. More viscous
2. As magma rises -> surface, dissolved gases in magma cannot escape easily
3. More pressure builds up -> gases escape explosively
28
Is high silica magma in stratovolcanoes or shield volcanoes?
**BOTH**
- More associated with stratovolcanoes
29
How does low silica magma lead to gentle, e___ explosions?
1. Less viscous magma
2. Magma rises to surface -> dissolved gases escape easily
3. Less pressure builds up -> gentle, **effusive** explosions
30
What is viscous?
Thick, sticky consistency
## Footnote
Just imagine the thick, sticky magma. Gases would obviously find it harder to escape through **thicker and sticker magma**
31
what is effusive eruption characterized by? (4)
- gentle
- mainly lava outpouring into ground
- no tephra ejected
- non-explosive
32
Is low silica magma in stratovolcanoes or shield volcanoes?
**BOTH**
- More associated with shield volcanoes
## Footnote
Shield = defensive
Therefore strato = offensive
"Defensive Volcano" will eject a gentler, effusive eruption
33
How do stratovolcanoes form? (4 points)
1. High viscosity magma, rises thru weak areas in crust -> Earth's surface, erupts **explosively** as lava, ash, rocks
2. Ash, rocks settle on sides of volcano, later covered by lava
3. After **successive** eruptions, tall volcano consist of alternating lava, ash layer develop
4. Highly viscous lava travels shorter distance before cools, solidifies -> volcano has **steep sides, narrow summit**
| o3o pattern does not equal to made smhh
34
How does shield volcanoes form?
1. Low viscosity magma rises thru weak areas in crust -> Earth's surface, erupts **effusively**
2. After **successive** eruptions, volcano consisting of **layers of lava** develops
3. Less viscous lava travels **longer distance** before cools, solidifies, volcano has **gently sloping sides**, **broad summit**
35
How is volcano intensity measured?
Volcanic Explosivity Index scale
36
What does VEI scale base itself on?
- Vol. of ejected material
- Height of eruption cloud
- Duration of eruption
37
VEI scale characteristics
- Measured on scale of 0-8
- Effusive eruptions given value of 0-1
- 8 = mega colossal explosive eruption
- Logarithmic scale
38
Recap from Tect.1: What is logarithmic scale?
Increase of "1" in scale = 10 times more powerful than prev. no
39
# Numbers! Numbers! Numbers!
Amount of material ejected from effusive eruption VS mega-colossal explosive eruption tephra and eruption cloud
**effusive**
- <0.0001km^3 material ejected
**mega-colossal (VEI > 8)**
- >1000km^3 tephra
- >25km eruption cloud column
40
What is tephra
- any type/size rock **fragment**
- forcefully ejected
- travel airborne path (during eruption)
41
What is volcanic cone
triangle-shaped hill/mountain formed as lava accumulates around vent
42
What is magma chamber
Location in Earth's crust where magma located
43
what is crater
Bowl-shaped depression at top of volcano
44
what is lava
molten rocks erupted onto Earth's surface
45
what is conduit?
central passageway in volcano which magma travels through
46
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
47
what is magma
molten rocks found below Earth's surface
48
what is active vent
opening on Earth's surface through which lava erupts, situated at bottom of crater
49
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*
50
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
51
# Give specific examples.
Where is the largest concentration of earthquakes in?
**Pacific Ring of Fire**
52
Which, out of the 3 plate boundaries do earthquakes occur more commonly in?
**Convergent**
More stress built up during subduction
53
What is the Pacific Ring of Fire?
Broad belt around Pacific Ocean where most earthquakes, active volcanoes occur
54
Which plate boundaries does the Pacific Ring of Fire contain?
- Convergent: Pacific + Phillippine
- Divergent: Pacific + Cocos
- Transform: Pacific + North American
## Footnote
**refer to plate tectonic map for clearer view**
55
Where are volcanoes generally found?
Example of quantity of volcanoes found in these boundaries
Convergent (except C-C convergence) + divergent boundaries
**Convergence**
- Belt of volcanoes along Pacific Ring of Fire's convergent plate boundaries' **subduction zones**
**Divergence**
- Belt of volcanoes along divergent plate boundaries between NA and Eurasian Plates
56
Any volcanoes at transform plate boundary?
No
- Magma does not rise to Earth's surface to form volcanoes
57
What are hot spot volcanoes?
Volcanoes that develop over into hot regions in mantle
- **May** develop in locations away from plate boundaries
58
General hazards of earthquakes
- Ground shaking
- Soil liquefaction
- Landslides
- Tsunamis
59
General hazards of volcanic eruption
- Tephra
- Volcanic gases
- Lava flows
- Pyroclastic flows
- Lahars
- Volcanic landslides
60
What is distribution?
Way that something is spread out/arranged over geographic area
61
What is a secondary cone? When does it form?
Small volcano formed on side of main volcano
**forms when:**
1. pressure builds up
62
What is soil liquefaction?
Phenomena where **saturated, lose soil** loses it's structure -> transforms into thick fluid (due to **ground shaking**)
63
Which boundaries do strato and shield volcanoes mainly lie on?
**Strato**: Converging
**Shield**: Diverging
64
What is pyroclastic flow
Hot clouds of gas, ash, rocks travelling down slopes of volcano at >200km/h
65
What is lahars?
Mudflows, comprising -> volcanic ash + water
66
What is tsunami?
Series of ocean waves
67
High silica magma = increased rate of flow.
Is this true?
no.
High silica = increased visocity = thicker = slower flow rate
68
Characteristics of earthquake hazards
- soil liquefaction, ground shaking, landslides **usually localized**
- found near plate boundaries
- **tsunamis** not located near epicenter (*can travel thousands of kilometers from pt. of origin*)
69
Characteristics of volcanic eruption
- volcanic gases, lava flows, pyroclastic flows, lahars, volcanic landslides localised
- volcanic ash unlocalised
- Volcanic ash can travel thousands of kilometers
## Footnote
Tephra is ambiguous as **some is too heavy to travel far.** some are quite small and have the potential to travel far away
70
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
71
What is geothermal energy?
- energy derived from heat in Earth's crust
72
what is weathering
breaking down/dissolving of rocks on Earth's surface
73
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
## Footnote
Not all have all four.
e.g. volcanic gses only has destroy ecosystem, properties, cause fatalities
74
How does ground shaking destroy ecosystems?
- ruptures chemical factories -> pollution
- fractures, uproot trees
75
how does ground shaking destroy properties and infastructure?
Weaken roads, buildings -> collapse -> difficult to rescue people/supply aid
76
How does ground shaking disrupt human services?
- snap waterpipes, result in water shortages
- snap communication+electricity cables, affect important comm. services
## Footnote
((Gas+Water Pipes Electricity+Communication Cables) e.g. snap waterpipes, result in water shortages)
77
How does ground shaking cause injuries and fatalities?
people trapped under collapsed infrastructure -> fatalities, injuries
78
how does soil liquefaction destroy natural systems?
- trees on liquefied soil sink, tip over, damage wildlife habitats, cause biodiversity loss
79
how does soil liquefaction destroy properties and infrastructure?
infrastructure sink into soil -> tip over -> make rescuing difficult
80
how does soil liquefaction disrupt human services?
- same as disrupts human services for ground shaking
- roads and railways above liquefied soil sinks -> difficult to rescue ppl
## Footnote
((Gas+Water Pipes Electricity+Communication Cables) e.g. snap waterpipes, result in water shortages)
81
how does landslides destroy natural ecosystems
- fast-moving debris bury huge areas of forest, pollute rivers
- River blockages may cause **floods**
82
how does landslides destroy properties and infastructure
Debris bury villages, farms destroy infastructure
83
how does landslides disrupt human services
- Debris -> (same as groundshaking disrupt human services)
- roads, railways blocked by debris -> rescuing/aid more difficult
## Footnote
((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
84
how does landslides cause fatalities and injuries
- debris bury/hit people
- debris block rivers -> floods -> drown ppl
## Footnote
blocking rivers cause flood
flood cause
- drowning
- flood coastal areas e.g., kill wildlife
85
are tsunamis always caused by undersea earthquake
no.
- landslides can also cause it!
86
can tsunamis travel to the coastline?
yes!
Tsunamis can travel over thousands of km, devastate huge areas of coastline
87
5 parts: How do tsunami occur?
1. Undersea earthquake causes seabed to be displaced
2. Large vol. of water lifted, form waves of great wavelength, low height (<1m)
3. Waves travel -> land (high speed, >800km/h)
4. On approaching coast, greater friction w/ shallower seabed slows waves down
5. Waves get closer tgt -> increase in height (15m or more, 30-50km/h **onshore**)
88
# For tsunami, think about w___ and d____
how does tsunami destroy ecosystems?
- seawater flood huge coastal areas, wetlands
- large amt. of debris carried by waves pollute areas, kill wildlife
## Footnote
water and large amt of debris
89
# when think about tsunami, w___ and d____
how does tsunami destroy properties and infastructure?
- fast moving water, large amt. of debris carried in by waves -> sweep away infastructure
## Footnote
water and large amt of debris
90
how does tsunami disrupt human systems?
- fast moving waters, large amt. of debris (same as ground shaking affect human systems)
## Footnote
- water and large amt of debris
- snap (electricity, comm. cables)
electricity, gas, comm., water
91
how does tsunami cause injuries and fatalities?
- sweeping waters drown people
- large amts. of debris carried in by waves hit, injure, kill people
92
# Tephra, think about a___, v___ b____
How does tephra destroy ecosystems
- ash carried thousands of km away by **prevailing** winds, pollute huge areas o/ forests, rivers, habitats
- ash suffocate, kill wildlife
## Footnote
all about ash
93
# Tephra think about v__b__ and a__
How does tephra destroy properties and infastructure?
- volcanic bombs varying in size can hit properties, cause damage
- ashfall accumulation on roof of building
- ash + water -> double weight -> collapse buildings
- ash corrodes buildings, weakens structure
- ash damage farmlands, suffocate crops and livestock
## Footnote
yes, ash is corrosive, apparently
94
how big are volcanic bombs?
- from few cm to as big as a car
95
# tephra, think about a___ and v__b___
how does tephra disrupt human services?
- ash particles damage plane engines, disrupt air transportation
96
# 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
97
# when think about volcanic gases, 2 gases: s__ d___ and c___ d___
how does volcanic gases destroy ecosystems?
- sulfur dioxide causes acid rain when react w/ water in air, damage vegetation, kill wildlife
- cold carbon dioxide **heavier** than air, high conc. in low-lying areas like river valleys -> kill wildlife
## Footnote
high conc. in low lying areas as it sinks
**btw Co2 still in gaseous form tho it is cold.**
98
# when think about volcanic gases, 2 gases: s__ d___ and c___ d___
how does volcanic gases cause fatalities?
- sulfur dioxide irritate skin nose eye throat
- >3% conc. of carbon dioxide causes breathing difficulties, >15% conc. cause death
99
what gases does volcanic eruptions releaes
- sulfur dioxide
- carbon dioxide
100
chaare deaths caused by lava flow common?
no
- people easily move out of way
101
characteristics of lava flows
- extremely hot
- can be high silica/low silica
- travel over some distance from volcano
102
# Lava is h___
how does lava flow destroy ecosystem
- hot, low-silica lava travel over some distance, destroy forest, habitats
103
# Lava is h___
How does lava flow destroy properties and infastructure?
Burn through properties, infastructure
104
How does lava flow affect human services?
- (same as ground shaking destruction)
## Footnote
destroy: (water, gas pipes)
(electricity, comm. cables)
105
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
106
characteristics of pyroclastic flow
- >200km/h speeds
- 700deg celcius temp
- most devastating of all volcanic hazards
- travel several kilometers
107
Pyroclastic VS volcanic gases
**Pyroclastic**
- damn fast (>200km/h)
- most hot (700deg)
- gas, ash, rocks
**volcanic gases**
- sulfur, carbon dioxide
- acid rain (sulf. dioxide), suffocation (carb. dioxide)
- gases only
108
# think about t___, h___ f___, a__
how does pyroclastic flow destroy ecosystems?
- huge areas of forest destroyed
- thick layers of ash cover path of pyroclastic flows -> pollution of forests
## Footnote
ash, hot flows, temperatures
109
how does pyroclastic flow destroy properties and infastructure
hot flows burn through homes, infastructure
110
how does pyroclastic flow disrupt human systems
- hot flows (same as how human systems are affected by ground shaking)
## Footnote
hot flows destroy elecrticity, comm. cables, gas pipes, water pipes
111
how does pyroclastic flow cause injuries and fatalities
extreme temp. burn, kill people in fraction of a sec.
112
how are lahars formed
huge amts. of ash+rocks ejected during eruption mixed w/ water
113
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
114
how does lahars destroy ecosystems
- cover forest, ecosystems with thick mud
- pollute rivers, kill aquatic life
115
how dhow does lahars destroy properties and infastrcuture?
- bury houses, buildings
- cover properties w/ thick mud which hardens like concrete
116
how does lahars disrupt human services
- roads railways blocked by debris
- lahars can (same as ground shaking affect human services)
## Footnote
lahars can damage comm. + electricity cables, water, gas pipes => disruption of comm + water shortage + disrupt supply of gas
117
how doe lahars cause fatatlities?
- bury houses w/ residents, killing them
118
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
