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2017/2018 > EOS 170 II > Flashcards

EOS 170 II Flashcards

1
Q

meaning of ‘tsunami’

A 
tau = harbor
nami = wave
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2
Q

tsunami ≠ tidal wave

A

nothing to do with Earth’s tides

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3
Q

tsunami stages

A

generation
propagation
inundation

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4
Q

Generation, causes of tsunami

A

anything that displaces ocean water

  1. volcanoes
  2. landslides
  3. meteorite impact
  4. earthquake
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5
Q

tsunami generation, volcano

A

caldera collapse
pyroclastic flow
underwater eruption

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6
Q

examples of volcano-caused tsunami

A
  • Krakatau, 1883, caldera collapse

- Tonga, 2009, underwater eruption

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7
Q

example of landslide-caused tsunami

A

Lituya Bay, Alaska, 1958

wave up to 524m

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8
Q

example of impact-caused tsunami

A

Chicxulub, Mexico, 65Ma

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9
Q

earthquake-caused tsunamis

A

especially megathrust earthquakes at subduction zones

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10
Q

example of earthquake-caused tsunami, Indian ocean

A

‘boxing day’ tsunami, Dec 26, 2004

  • M9.2 megathrust eq
  • 3 largest ever recorded
  • 1300km rupture, 8 minutes to rupture
  • 230,000 deaths including ppl 6000km away in Africa
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11
Q

Tohoku tsunami

A

March 2011, Japan arc, triple junction, M9.0, thrust faulting, 18,500 deaths, 90% from drowning, ~360billion USD, ongoing costs associated w/ Fukushima

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12
Q

water waves

A

pulses of energy that move through a water mass causing water molecules to rotate in place

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13
Q

water wave particle motion

A
  • prograde (unlike Rayleigh waves - retrograde)
  • motion decreases with depth
  • motion stops at 1/2L
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14
Q

water waves less than 1/2L

A
  • orbits flatten into eclipses
  • wave slows down
  • wavelength decreases
  • water, energy concentrated
  • wave height increases
  • shoaling
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15
Q

wind wave size, frequency, velocity determined by

A
  • wind velocity
  • wind duration
  • wind consistency
  • area of water body
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16
Q

wind wave vs tsunami; period, WL, velocity

A

period: W (5-20s); T (3600s, 1h)
WL: W(40-600m); T(100s of km)
V: W(8-30m/s); T(200m/s)

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17
Q

real danger of tsunamis

A

-momentum: tremendous mass of water floods inland for several minutes

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18
Q

depth of tsunami wave that can kill

A

knee-high

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19
Q

long L and p of tsunami allows

A

wave to bend around land and hit multiple shores: wrapping/refracting

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20
Q

velocity of tsunami wave in deep water

A 
V = sqr. (gD)
g = 9.8m/s2
D = water depth
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21
Q

average tsunami velocity in PO

A 
D = 5500m
V = 230m/s average = 83/km/hr
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22
Q

run up

A

how far the waves go up the beach

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23
Q

shoaling

A

wave rising up

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24
Q

run up height/ distance

A

depends on nearshore bathymetry, shape of coastline

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25
Q

tsunami peaks

A
  • up to 10
  • separated by 10-60min
  • largest often not the first
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26
Q

when the first part of the tsunami wave to arrive is a trough

A

draw down

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27
Q

Tohoku tsunami run up

A
  • eq much larger than anticipated
  • tsunami run up much higher (40m)
  • went over tsunami wall
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28
Q

1700AD orphan tsunami

A
  • Jan 1700, 2m high
  • Felt in Japan
  • didn’t feel shaking from ‘parent eq’
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29
Q

ghost forest

A

trees killed as lowered into tidal zone (salt) by subsidence

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30
Q

tsunami recurrence in cascadia

A

400-600years

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31
Q

chance of subduction zone eq in cascadia

A

15% on 50 yr timescale

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32
Q

what would a cascade mega thrust tsunami look like

A
  • wave heights up to 15m, particularly in inlets (Port Alberni)
  • first reach Tofino
  • smaller in Vic (1-5m)
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33
Q

Lituya Bay

A
  • 1958 tsunami
  • M7.8 eq on Fairweather fault
  • huge rockfall at head of bay (30 mill. m3)
  • 500m high wave
  • 5 deaths
  • trees stripped
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34
Q

Greenland tsunami

A
  • Karrat fjord, June 2017
  • 11 houses gone, 4 deaths
  • M4.2 eq ?
  • landslide into water
  • large local tsunami
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35
Q

landslide tsunamis

A

devastating locally, no global effect

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36
Q

greenland tsunami earthquake

A
  • seismograms record waves equivalent to a M4 eq but wave structure diff. than normal eq. seismo (no p, s waves)
  • probably from the landslide
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37
Q

Grand Banks tsunami

A
  • Nov 1929, M7.2eq
  • triggered continental slope landslide – 200km3
  • turbidity current severed transatlantic -telegraph cables
  • generated tsunami waves
  • 28 deaths
  • deadliest recent eq in Canada (Nfdld)
  • tsunami 2.5hr after eq
  • 4-7m waves, 15-30m run up
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38
Q

expect a Grand Banks type tsunami here?

A
  • evidence of turbidity currents offshore cascadia
  • fraser river delta is steepening
  • 2m tsunami on Texada island 1946
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39
Q

standing wave, enclosed water, swaying back and forth

A

seiche

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40
Q

seiche cause

A
  • strong winds

- earthquake

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41
Q

example of wind seiche

A

trade winds blowing over lake Erie

  • winds pile water up
  • if winds slow, water sloshes back
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42
Q

Hebhen seiche

A

1959, Hebgen lake, SW Montana

  • M7.5eq - subsidence
  • dam foreman saw wall of water, then it disappeared
  • 17 min periods for 12hours
  • largest waves ca. 20ft
  • summer, families camping, 28 deaths
  • landslide also blocked river
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43
Q

PTWC

A

Pacific Tsunami Warning Centre

-1949, circum-pacific nation coordinated effort

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44
Q

what PTWC does

A

assess:

  • epicentre
  • depth
  • magnitude
  • travel time for tsunami waves
  • initiate tsunami watch
  • upgrade to tsunami warning
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45
Q

PTWC, depth

A
  • was eq shallow enough to generate tsunami

- less than 100km

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46
Q

DART

A

deep-ocean assessment and reporting of tsunamis

  • ocean bottom pressure sensors
  • feel tsunami waves pass
  • send message through acoustic telemetry, satellites
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47
Q

tsunami mitigation

A
  • early detection
  • structural countermeasures
  • tsunami hazard maps
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48
Q

tsunami structural countermeasures

A
  • tsunami walls
  • breakswaters
  • underwater berm
  • angled walls/ditches
  • evacuation, raised earth park
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49
Q

tsunami hazard maps

A
  • use shape of coastline, bathymetry

- predict wave heights at diff. points along coast

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50
Q

mass movement

A
  • movement of large volume of material downslope

- influenced by gravity

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51
Q

types of mass movement classified according to

A
  1. material being moved

2. how it moves

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52
Q

mass movement hazards in canada

A
  • no top ten events since 1970s

- most of worst disasters in eastern Canada, especially Quebec

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53
Q

mass movement fatalities

A

2004-2010: 32,000 deaths from 2600 landslides

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54
Q

mass movement triggers

A
  • earthquake
  • heavy rainfall
  • freeze-thaw weathering
  • human construction
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55
Q

underlying conditions of slope instability

A
  • adding mass on slope
  • removing support
  • reducing internal strength of rock
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56
Q

water and mass movements

A
  • externally (rivers, waves)- undercut steep slopes
  • mobilize sediment
  • clays add to sliding
  • porosity, weight
  • dissolution
  • pore water pressure
  • freeze/thaw
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57
Q

clay, mass movement

A
  • platy, sheety minerals
  • expand when wet, absorb water
  • lubricate layers
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58
Q

clay formation

A

by-product of ice grinding on bedrock, common in formerly -glaciated regions

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59
Q

sedimentary rock porosity

A

typically 10-30%

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60
Q

water and porosity

A

replacing air w/ water increases weight

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61
Q

soil porosity

A

50%

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62
Q

dissolution

A

groundwater dissolves cements decreasing rock strength

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63
Q

pore water pressure

A
  • added sediment on top increases weight and P

- increased P packs grains tighter but water is incompressible and stores built-up pressure, weakens rock

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64
Q

freeze-thaw weathering

A
  • water enters crack

- freezes, expands, cracks rock

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65
Q

geology and mass movement

A
  • pre-existing geological conditions

- orientation

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66
Q

pre-existing geological conditions

A
  • poor cementation = crumbly

- bedding planes = weaknesses

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67
Q

geology orientation

A
  • weaknesses angled into slope = stronger
  • weaknesses parallel to stope = stronger
  • weakness parallel = whole slab break free
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68
Q

tectonics and mass movement

A

eq’s provide ground acceleration

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69
Q

Mass movement classification

A
  • direction of movement
  • speed
  • water content
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70
Q

Falls

A
  • individual blocks detach along fractures

- free-fall

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71
Q

Flows

A

also avalanche

  • material deformed as it moves (includes creep)
  • move as viscous fluid
  • turbulent movement over landscape
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72
Q

MM classification by direction of movement

A

down: falls, subsidence

down and out: slides, flows/avalanche

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73
Q

slow MM

A
  • earthflow
  • soil creep
  • rarely kill
  • infrastructure damage
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74
Q

catastrophic MM

A
  • debris flow
  • snow avalanche
  • rock falls
  • deadly
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75
Q

intermediate MM

A
  • translational slide
  • rotational slide
  • sometimes catastrophic
  • sometimes slow
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76
Q

rate of movement vs water content, MM

A

high speed: rockfall, loess flow, snow avalanche, debris flow
low speed, low water: creep
high water, low speed: earth flow, slow subsidence

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77
Q

material collapses into a void

A

subsidence

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78
Q

slide

A

well defined failure surface and limited deformation of moving material

  • semisolid mass
  • some coherence within mass
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79
Q

mechanics of soil creep

A
  • slowest
  • most common slope failure
  • freeze/thaw, wet/dry, heat/cool cycles of clay minerals
  • expands perpendicular to slope
  • contracts vertically due to gravity
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80
Q

earth flow

A
  • downslope viscous flow of fine grain saturated material

- btw soil creep and catas. debris flow

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81
Q

earth flow example

A

Slumgullion, Colorado

  • slow enough that trees grow and a road crosses it
  • few cm/week
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82
Q

debris flow

A
  • water-laden mass of soil, rock frag.s
  • rush down, funnel into streams
  • entrain objects in path
  • thick muddy deposits
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83
Q

rockfall

A
  • free fall of rock block from free face

- when elevated masses separate along fracture

84
Q

rock avalanche

A
  • rock fall turned into rock avalanche

- if hit steep scree slope

85
Q

rock avalanche common

A

flanks of volcanoes

86
Q

scree

A

a mass of small loose stones that form or cover a slope on a mountain

87
Q

rock slide

A
  • movement of rock above failure surface

- characteristic geomorphology

88
Q

rock slide type

A
  • rotational (concave failure surface)
  • translational (planar failure surface)
  • debris slide (rock fragments into debris)
89
Q

rockslide geomorphology

A
  • crown
  • head scarp
  • head
  • minor scarp
  • foot
  • cracks, ridges
  • toe
90
Q

rotational landslide movement

A

-rotational about axis parallel to slope

91
Q

rotational landslide materials

A
  • driving mass -> head of slide

- resisting mass -> toe of slide

92
Q

how far rotational slide travel

A
  • short distance typically

- motion decreases driving mass, increases resisting mass

93
Q

composite landslide

A

-start as one type and evolve into another

94
Q

composite landslide example

A

NZ, 2017

  • triggered by cyclone Debbie
  • starts as rotational rock slide
  • morphs into fluid debris slide
95
Q

Oso landslide

A

2014

  • 150-200% normal rainfall
  • steep ridge
  • river erodes soil along bank
  • unstable layers of sand, silt, clay
  • destabalized cliff from earlier slide, 2006
  • rotational landslide –> debris slide
  • 43 deaths
96
Q

how the 2006 slide affected the 2014 slide, Oso

A
  • ‘doorstop shelf’ buttress upper slope

- slide undercuts shelf, removed material supporting upper slope

97
Q

wasn’t likely a factor in Oso slide

A

logging

-lidar reveals scars and deposits of landslides far older than logging activity

98
Q

long runout landslide

A

Sturzstrom
‘fall’ ‘stream’
-soil, rock w/ horizontal movement&raquo_space; vertical

99
Q

Sturzstrom example

A
  • Collbran mudflow, colorado
  • blackhawk slide, California
  • Mt Meager
100
Q

Mt Meager sturzstrom

A

August 2010

  • 50 mi m3 rockfall high up
  • turned into giant debris flow travelling down creeks into Lillooet river
  • no deaths
  • seismometer signal equiv. to M3 eq
  • 13km horizontal., 2km vertically
  • 10º angle
101
Q

Landslide mitigation

A
  • scaling
  • benching
  • unloading the head
  • reinforcing the body (meshing, bolts)
  • supporting the toe (add material, breakwater)
  • drainage channels
102
Q

scaling

A

remove loose rock

103
Q

what are the main differences between debris flow and rock slide

A
  • debris = rock, mud, tree

- flow = fluid behaviour

104
Q

Volcano classification

A
  • active
  • dormant
  • inactive
105
Q

deaths in the past 50 years from volcanoes, landslides

A

volcano- 30,000
eq- around 1 million
landslide- around 150,000

106
Q

Volcano fatalities

A
  • volcano-triggered lahars

- densely-populated areas

107
Q

densely populated volcano cities

A

Napoli, Mt Vesuvius, Italy

  • 3 million
  • 1631 eruption killed 3360
108
Q

molten rock on earths surface

A

lava

109
Q

forms of lava

A

ash
bombs
flows
lahars

110
Q

molten rock within Earth

A

magma

111
Q

most abundant volatile in magma

A

H2O

112
Q

gas solubility increases w/

A

pressure

decreased T

113
Q

solidified lava above surface

A
  • volcanic or extrusive rocks
  • rhyolite pumice (continental)
  • basalt (oceanic)
114
Q

solidified magma

A
  • plutonic, intrusive rocks
  • granite (continental)
  • gabbro (oceanic)
  • larger crystals due to slow cooling
115
Q

Magma/lava viscosity depends on

A
  • T
  • crystal content
  • silica content
116
Q

Temperature and lava

A

higher T = lower V

117
Q

mineral crystal content and lava

A

higher crystal = higher V

118
Q

Si content

A

SiO2 increase V

119
Q

SiO2 and crust

A

continental: 60% SiO2
oceanic: 48% SiO2
i. e. continental&raquo_space; viscous

120
Q

explosiveness depends on

A

magma visocsity - controls amount and ease of volatile release

121
Q

low viscosity magma

A

= easy gas escape

= peaceful eruption

122
Q

3 magma types

A
  • basalt
  • andesite
  • rhyolite
123
Q

last crystallizing minerals

A

Rhyolite

  • lowest melting point
  • less SiO2
  • increased viscosity
  • higher gas content
  • more explosive
124
Q

Andesite

A

intermediate magma

  • mixed basaltic magma and continental crust
  • intermediate viscosity, gas content, explosivity
125
Q

Basalt

A

first crystallized minerals

  • highest melt point
  • melted mantle material
  • lowest SiO2, viscosity, gas content, explositivity
126
Q

80% of erupted magma

A

spreading centres

127
Q

MOR volcanism

A
  • low SiO2
  • decompression melting
  • high T, low Visc, low volatile
128
Q

formation of andesite/rhyolite

A
  • plate subduction of hydrated minerals
  • P releases water - promotes melting
  • magma rises through 40+km of crust
  • magma melts surrounding continental rocks – mixing
129
Q

10% of all magma erupted

A
  • volcanic arcs above subduction zones (10%)

- hot spots (10%)

130
Q

eruptive styles of plate tectonic settings

A
  • transform fault: little-no
  • spreading centre: peaceful
  • subduction zone: explosive
131
Q

how a volcano erupts

A
  • deep heat rises
  • decreased P, decompression melting
  • heat transfer melting of surrounding rock
  • formation of gas bubbles propels magma up
  • bubble volum overwhelms magma, explosion
  • plume in air
132
Q

magma at depth, gas

A

high P keeps volatiles dissolved in solution

-gases only form as P decreases

133
Q

types of volcanic eruptions

A

Non explosive: 1. Icelandic, 2. Hawaiian

Explosive: 3. Strombolian, 4. Vulcanian, 5. Plinian

134
Q

Volcanic gases (elements)

A

H, O, C, S, Cl, N

135
Q

Volcanic gas composition

A

H20 = 90%
CO2, CO, N2, H2, H2S, SO2, HCl, CH4
SO2, H2S = rotten egg smell

136
Q

Magma minerals

A

Si, Mg, Fe

+ leeched minerals: Al, Ca, K, Na

137
Q

volcanic soils

A
  • from weathering

- excellent fertilizers, amongst the most fertile (especially the K)

138
Q

basalt eruption underwater

A

pillow basalt

  • glassy from rapid quenching by cold water
  • 10cm - several m’s
139
Q

lava flows

A
  • sub-aerial eruptions
  • pahoeohoe
  • ‘A’a
140
Q

pahoehoe

A
  • very low viscosity lava

- smooth, ropy surface

141
Q

chunks of magma and volcanic rocks

A

pyroclastic debris

-fine ash, coarse ash, cinders, blocks and bombs (m+)

142
Q

volcanic material that is solid while airborne

A

blocks

143
Q

pyroclastic debris is ejected as

A

air fall

pyroclastic fall

144
Q

pyroclastic fall

A

material too dense to be carried up in plume

-chaotic w/ little-no sorting

145
Q

‘A’a

A

‘stony rough lava’

  • viscous lava
  • rough, jagged surface
  • broke blocks and vesicles
146
Q

volcanic material that is liquid while airborne and solidify after landing

A

bombs

147
Q

air fall

A

pyroclastic debris carried up in volcanic plume

-sorted into size layers

148
Q

very quickly cooling magma

A
  • glass
  • obsidian
  • no crystallization
149
Q

frothy glass

A

pumice

  • 90% air
  • can float on water
  • mostly rhyolitic or andesitic
150
Q

volcano type and viscosity

A 
Icelandic: low
Hawaiian: low
Stombolian: low -med
Vulcanian: med-high
Plinian: high
151
Q

volcano type and volatility

A 
Icelandic: low
Hawaiian: low
Stombolian: med
Vulcanian: med-high
Plinian: high
152
Q

volcano type and composition

A 
Icelandic: basalt
Hawaiian: basalt
Stombolian: basalt- andesite
Vulcanian: any type
Plinian: andesite- rhyolite
153
Q

Volcanic landform =

A

Viscosity + Volatiles + Volume

154
Q

Shield volcano

A

Viscosity: low
Volatility: low
Volume: large

155
Q

Flood basalt

A

Viscosity: low
Volatility: low
Volume: very large

156
Q

Viscosity: high
Volatility: high
Volume: very large

A

Caldera

157
Q

Viscosity: low- med
Volatility: med-high
Volume: small

A

Scoria cones

158
Q

lave dome

A

Viscosity: high
Volatility: low
Volume: small

159
Q

Viscosity: med-high
Volatility: med - high
Volume: large

A

stratovolcano

160
Q

Hawaiian-type eruption

A

low viscosity and volatiles, high volume

  • basalt lava spills out of fissures as lava fountain, flows down slope as hot lava river
  • days - years
161
Q

long developed Hawaiian type eruption

A

shield volcano

-width&raquo_space; height

162
Q

Mauna Loa

A

shield volcano

  • 9km above abyssal plain
  • 4km above sea-level
  • 2ookm wide
  • largest sub-aerial volcano on E
163
Q

Icelandic-type eruption

A
  • low viscosity and volatility
  • most peaceful
  • basaltic lava out linear vents/fissures
  • create wide volcanic plateaus
164
Q

the 3 explosive volcano types named after

A 
volcanoes in Italy
-Stombolian: Stromboli
-Vulcanian: Vulcano
-Plinian: Vesuvius
subduction of Ionian sea forms Calabrian Arc volcano chain
165
Q

Strombolian-type volcano

A
  • intermediate viscosity and volatile, small volume
  • basalt-andesitic
  • mildly explosive
  • not very powerful
166
Q

Stromboli

A

‘lighthouse of the Mediterranean’

  • has erupted almost daily for millennia
  • bursts of lava few times/hr
  • bombs reach tens-hundreds of m’s
167
Q

wide volcanic plateau formed by icelandic-type eruption

A

flood basalt

168
Q

strombolian-type eruptions associated w/

A

scoria cones/ cinder cones

-modest conical hills of tephra

169
Q

cinder cones in BC

A

Tseax cone, Stikine volcanic belt

Kostal cone, Wells Gray

170
Q

Tseax cone

A
  • erupted 1700 AD
  • Canadas worst natural disaster
  • may have been triggered by megathrust
  • 2000 First Nations died
171
Q

deaths from Tseax cone

A
  • asphyxiation from CO2

- CO2 denser than air, displaced O2

172
Q

vulcanian-type eruptions form what type of volcanoes

A

stratovolcanoes

  • tall, steep-sided, symmetrical peaks
  • alternating ash/rock
  • viscous magma
  • some contain craters on top
173
Q

stratovolcano examples

A
  • Mt Baker
  • Mt Rainier
  • Mt Fuji
174
Q

number vulcanian eruptions

A

3-5/yr

175
Q

Plinian-type eruption

A
  • high magma and volatility, very large volume
  • most violent
  • powerful eruption column of gas, ash, rock > 10km
  • andesitic or rhyolitic
  • few /yr
176
Q

Plinian-type volcano eruptions form

A
  • startovocanoes

- calderas

177
Q

caldera

A

collapsed cone formed form emptying of magma chamber

178
Q

eruptive sequence

A

early phase: Vulcanian-type (clearing the throat)

final phase: Plinian-type (throat is clear)

179
Q

Ultra-Plinian

A
  • very largest eruptions

- columns >25km high and volumes >10km3

180
Q

VEI

A

volcanic explosively index

  • 0-8
  • calculated based on material erupted, height of column, duration of major eruptive blast
181
Q

pyroclastic flow

A

-fast-moving gravity current of hot tephra + gas

182
Q

pyroclastic flow trigger

A
  • collapse of volcanic dome
  • spillover from crater
  • direct blast from explosive eruption
  • collapse of eruption column
183
Q

‘flow’ of pyroclastic flow

A
  • fluidized from water, gases in eruption

- overrides cushion of air

184
Q

pyroclastic flow speeds

A

small: 20m/s
large: 200m/s (700km/hr)

185
Q

pyroclastic flow temperatures

A

1000ºC

186
Q

lahar

A

mud/debris flow of pyroclastic material mixed w/ rocky debris + water

  • travel down valleys
  • 1-40 m/s
  • travel 100s of kms
187
Q

formation of lahars

A
  • volcanic debris avalanche mixes w/ snow/ice
  • pyroc. flow diluted w/ river water, meltwater as they travel
  • natural failure of a crater lake
  • rainfall on loose tephra
188
Q

lahars that occur after eruption

A

secondary lahars

189
Q

factors affecting lahar speed, power

A
  • gradient
  • viscosity (water)
  • containment (narrow channel restricting water increases flow)
190
Q

Tephra falls

A

Mount St Helens

191
Q

Pyroclastic flows

A

Mount St Helens

Pomeii/Vesuvius

192
Q

Lahar

A

Mount St Helens

Nevado del Ruiz

193
Q

Mount St Helens

A 
May 1980
57 deaths
1 billion in damage
Cascade volcanic arc
-M5.1 eq triggered landslide
194
Q

continuation of cascade volcanic arc into BC

A

Garibaldi Volcanic Belt

-less active

195
Q

most active cascade volcano

A

mt st helens

-activity occurs in burst decades to hundreds of yrs

196
Q

Mount St Helens height

A

built up from 4 millennia of strombolian and vulcanian lava flows and pyroclastic flows

197
Q

destabilization of MS Helens

A

rhyolitic lava dome and andesitic flows 1800s

198
Q

MSH earthquake swarms

A

1980

  • acceleration magma movement
  • rising caused bulge on N side outward up to 120m
199
Q

most of MSH deaths

A

loggers who ignored no go zone exec order

200
Q

MSH bulge explosion

A

M5.1 eq triggered landslide – released pressure – lateral blast – pyroclastic flows – melted glaciers – lahars

201
Q

MSH damage

A
  • downed 550km2 of trees
  • damaged 27 bridges, 200 homes
  • clogged Columbia river, closed port of Portland
  • 57 deaths
  • highways closed for weeks
  • 1000 flights cancelled
  • ash over 60000km2
202
Q

MSH Vulcanian eruption

A

lateral blast cleared the throat - released pressure - allow more bibles to form - allow 9hr long Plinian eruption

203
Q

MSH Plinian eruption

A
  • 9hrs
  • 20km high cloud
  • 540 million ash
  • tephra fall-out hazard for weeks, >400km away
204
Q

MSH doming

A

-dome growth fed pyroclastic flows

205
Q

evidence of the 1700AD orphan tsunami

A
  • oregon, washington ghost forests w/ radiocarbon dating and tree ring studies
  • tsunami reports in Japan
206
Q

do some oceans have more tsunamis than others

A

yes, Atlantic does not have subduction zones

207
Q

Atlantic earthquakes

A

no subduction zone eq’s

  • Grand Banks, Nwfld, submarine slide
  • Karrot Fjord, Greenland, landslide

2017/2018 (7 decks)

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