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Natural Hazards and Disasters > test 2 > Flashcards

test 2 Flashcards

1
Q

how many volcanos erupt a year

A

50-60

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2
Q

how people live in the vicinity of volcanos and what are the locations

A

500 million ppl
Japan, Mexico, philippines, indonesia, western north america

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3
Q

Is the distribution of volcanos random or not random?

A

Not
Occur in well defined zones or belts

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4
Q

2/3 of all active volcanos on land are located along _____

A

the ring of fire

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5
Q

tectonic setting determines:

A

The type of volcano
-mid ocean ridges, subduction zones, and hot spots

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6
Q

magma

A

molten rock below earth surface

becomes lava when reaches surface

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7
Q

viscosity of magma is controlled by

A

composition, mainly through silica content

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8
Q

silica affects ___

A

viscosity

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9
Q

how does silica rich magma flow ?

A

not easily

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10
Q

what does viscosity effect?

A

the flow of lava, the shape of the resulting volcano

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11
Q

high silica content

A

70-75%
High viscocity

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12
Q

intermediate silica content

A

60 - 65 %
intermediate viscosity

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13
Q

low silica content

A

50-55%
low V

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14
Q

limited silica content

A

below 40%
very low V

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15
Q

Lava Flows: Pahoehoe

A

Average flow rates - 30 km/h
Most flows travel between 10 and 50 km from the source

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16
Q

Kilimanjaro hasnt erupted in how many years?

A

2.5 billion

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17
Q

What are the shape and eruptive style of a volcano related to?

A

The chemistry and viscosity of their magmas

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18
Q

Types of Volcanos: Stravolocano / composite cone

A

Composition : andensite
Volatile Content: high
Shape: coned, steep sides, built of lava flows, and protoclastic cones
ex: mount Shasta California, mount helens, Washington

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19
Q

Types of Volcanos: Lava Dome

A

Comp: andesite to rhyolite
Volatile Content: low to moderate
Shape: dome shaped, steep sides
Eruption Type: effusive w/ lava piling up near the vent, can be explosive
ex: mount lassen, California

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20
Q

types of volcano: shield

A

Comp: basalt
V.C: low
Shape: gentle arch, shield shape, shallow slopes, built up of mainly lava flows
eruption type: traveling lava flows
Ex. Mount loa - hawaii

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21
Q

Types of Volcanos: Cinder Cone

A

Comp: basalt
V.C: low to moderate
shape: steep sides, coned, summit crater
Eruption type: mostly tephra ejection (nut to fist sized) lava flows
ex. SP Crater, Arizona

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22
Q

Types of Volcanos: continental calderas

A

Comp - rhyolite
VC: high
Shape: broad uplift w/ large summit depression
ET: tephra
ex: Yellowstone caldera , mount Manama

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23
Q

pyroclasts

A

magma fragments that are explosively ejected by volcanos and are mostly solid

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24
Q

pyroclastic materials

A

Ash : less than 2 mm diameter
Lapili : 2-64 mm diameter
bombs: part molten, less than 64 mm d
blocks: solid, less than 64 mm d

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25
Q

volcanic gases

A

mostly water vapor

erupted sulfur can have significant effects on climate

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26
Q

erupted sulfur effects on climate leads to lesser amounts of ………

A

carbon dioxide
nitrogen
sulfure dioxide
hydrogen sulfide

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27
Q

caldera

A
  • the summit of a volcano collapse into its magma chamber following voluminous eruptions

-can be 1000s of meters across and 100s of meters deep

-can host lakes or become sites for new volcanic activity

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28
Q

hot springs

A

-geothermal activity
-hot rocks heat groundwater discharged at surface

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29
Q

gysers

A

-groundwater builds, erupting steam at a surface

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30
Q

what are pyroclastic flows?

A

huge sheet like eruptions of pyroclastic materials

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31
Q

ice contact volcanos

A

volcanos that erupt beneath or against glaciers

when they erupt the heat from the lava can melt the surrounding ice causing unique volcanic features and hazards

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32
Q

primary effects of volcanos

A

lava flows, ash fall, volcanic bombs, pyroclastic flows and surges, lateral blasts, poisonous gases.

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33
Q

secondary effects of volcanos

A

lahars, debris avalanches, landslides, groundwater and surface contamination, floods, fires, tsunamis.

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34
Q

how can the size of an eruption be quantified ?

A

by using the volcanic explosivity index

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35
Q

volcanic hazards - lava flows

A

Occurs when magma reaches surface
-moves fast or slow depending on viscosity and temp
-high viscosity moves slower

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36
Q

ways to divert lava flows

A

Barriers
Hydraulic chilling
diversion walls

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37
Q

volcanic hazards - pyroclastic flows

A

Avalanches of hot rock, ash, volcanic rock fragments
-hot and race down at 400km/h

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38
Q

volcanic hazards - pyroclastic surges

A

Dense clouds of hot gases and rock debris produced by explosive interaction of water and magma

39
Q

Volcanic hazards : lateral blasts/explosive eruptions

A

Rock frag, gas, ash, are blown from side of volcano
ex.mount st helens 1980

40
Q

volcanic hazards: lahars

A

Large amounts of loose volcanic ash and other pyroclastic material becomes saturated with water and rapidly move down slope

41
Q

Links between volcanos and other ND’s

A

fires
landslides
earthquakes
climate change

42
Q

why do people live near volcanos

A

fertile soils
source of power (geothermal energy)
mineral resources
recreational oppurtunities
creation of new land

43
Q

red river flood 1997 Winnipeg

A

heavy snow pack - warming weather and rain

covered 2560km 2 (southern Manitoba, parts of North Dakota)

3 ppl dead

815 mil in damage

44
Q

hydrologic cycle

A

Streams and rivers are part of this cycle
Evaporation of water from earths surface
water returns to ocean underground or across the land

45
Q

gradient

A

Slope of the land which the river flows
Steepest at high elevations
Levels off as river approaches its base
Shown on longitudinal profile

46
Q

cross sectional profile

A

Steeper side and deeper valley near headwaters
Wide floodplain usually present at base level
Differences due to higher flow velocity at higher elevations

47
Q

As longitudinal profiles gown down a river….
Discharge ___
river width _____
river velocity _____
sediment size ____
sediment amount ___ and river slope ______

A

Increases
Increases
stays the same or slightly increases
decreasees
increases and decreases

48
Q

discharge

A

The water volume flowing through a cross section

49
Q

drainage baisin

A

Land that slops towards the sea separated by topographic ridges

50
Q

4 major drainage baisins

A

Atlantic basins
Hudson Bay
arctic baisin
pacific baisin

51
Q

River model stages

A

Youthful
Mature
old age

52
Q

Youthful river stage

A

V shaped
Upper parts where there is steeper topography and more precipitation
water velocity is fast, down cutting, and erosion occur
coarse material in river
river often flowing over rock
river dominates bbottom of valley

53
Q

Meandering patterns

A

Channel bends called meanders that migrate back and forth across the floodplains

54
Q

floodplains

A

area of low-lying ground adjacent to a river, formed mainly of river sediments and subject to flooding.

55
Q

River flow and sediment transport process

A

1 river flow
2 sediment transport
3 erosion and deposition

56
Q

The wide, flat region adjacent to a river

Sediment frequently deposited in river bars or on floodplain

areas that are able to be flooded periodically by the rivers

A

broad valley bottom

57
Q

sediment loss and depositional landforms

A

Where river loses its load
May have fans or deltas as depositional landforms
sediment can be swept away into lakes or seas

58
Q

Total load consists of:

A

Bed load
suspension load
dissolved load

59
Q

Materials that roll, slide, bounce along bottom

A

bed load

60
Q

Slit and clay particles that are carried into the water

A

suspension load

61
Q

Materials carried as a chemical solution

A

dissolved load

62
Q

Magnitude and duration of a flood are determined by:

A

Amount and distribution of a precipitation in drainage basin

Rate at which the precipitation soaks into earth

how fast a surface runoff reaches river

amount of moisture in soil

63
Q

primary effects of flooding

A

Drainage caused by currents, debris, sediment to farms, homes, buildings, roads, etc..

Erosion and deposition of sediment related to loss of soil and vegetation

64
Q

Secondary effects of flooding

A

short term pollution of rivers
Hunger and disease
homelessness

65
Q

Service functions : fertilize lands

A

Service functions : fertilize lands

66
Q

Service functions : aquatic ecosystems

A

Flooding clears rivers of debris and sweep nutrients

67
Q

Service functions: sediment supply

A

Periodically flooding builds up elevation

68
Q

Dam construction : upstream

A

As water enters reservoir, it slows, deposits sediment, and forms a delta

69
Q

Dam construction : downstream

A

As water leaves dam, it is devoid of sediment and can erode sediment to transport instead of depositing

Slopes of the stream will decrease until equilibrium is reached

70
Q

Human interactions : urbanization

A

ncreases magnitude and frequency of floods

Urban areas have impervious and greater storm servers

Bridges block debris, creating dams

Urban runoff can be 5x more than pre-urban conditions

71
Q

levees

A

Barriers to keep flood waters contained

Breaks cause higher energy flows

can produce bottlenecks in upstream areas

need to be maintained

72
Q

channelization

A

Straightening, deepening, widening, cleaning, or lining existing stream channels

Have adverse affects on fish and wetland wildlife

can cause benefits to some urban and rural areas and improves navigation

73
Q

Minimizing flood hazards - channelization
Create a natural channel by allowing the stream to meander and reconstruct variable water flow conditions by:

A

Clearing urban waste to allow free flow

Producing existing channel banks by not removing trees

planting additional trees or vegetation

74
Q

adjustments - flood insurance

A

Maps of 100 yr floodplain where created to determine risk

New property owners are required to buy flood insurance

building codes limit new construction on floodplain

codes prohibit building on 20yr floodplain

75
Q

flood proofing

A

Raise foundation of buildings above flood hazard level

Constructing flood walls or mounds

using waterproofing construction

installing improved drains and pumps

76
Q

landslide

A

is slow or rapid nearly vertical downward
movement of Earth’s surface

77
Q

karst

A

Landscape resulting from ,
dolostone, marble, gypsum or rock sal

78
Q

Soil expansion and contraction

A
  • Changes in water content of soil
  • Freezing and thawing
  • Not usually life threatening, but are some of the most
    widespread and costly natural hazards.
79
Q

sinkhole

A

A depression or hole in the ground caused by the collapse of a surface layer, which can range from a few meters to several hundred meters in diameter.

80
Q

subsidence

A

the gradual settling or sudden sinking of the ground surface, which can also create depressions that may vary in size.

81
Q

permafrost

A

Soil or underwater sediment that stays completely frozen for 2 years or more

refreezes in winter,
thaws in summer

  • When thawed, it can
    create land subsidence
  • Extensive thawing creates
    uneven soil called thermokarst
  • Frost-susceptible sediments
    expand when they freeze
  • Causes frost heaving
82
Q

permanently frozen ground that remains frozen all year round, found mainly in very cold regions

A

Continuous
permafrost

83
Q

ground that has patches of permanently frozen soil, but some areas thaw during the summer.

A

discontinous permafrost

84
Q

when permafrost exists in small, isolated patches that are surrounded by thawed ground.

A

sporadic permafrost

85
Q

Climate controls the amount and timing of …..

A

rainfall and
duration of freezing temperatures

86
Q

Sinkholes are common in…

A

humid climates

87
Q

Expansive soils are common in areas with…..

A

wet and dry
seasons.

88
Q

Collapsible soils are found in….

A

arid and semi-arid climates

89
Q

Areas with extensive, below-freezing temperatures can host…..

A

frost heaving

90
Q

Effects of Subsidence and Soil Volume Change
Sinkhole formation

A

Damage highways,
homes, sewage facilities,
etc.
* Probably triggered by
fluctuations in water table

91
Q

Effects of Subsidence and Soil Volume Change

Groundwater Use and
Contamination

A

Caves create direct
access between surface
and groundwater.

  • This access can make
    water vulnerable to
    pollution, especially
    during drought and when
    sinkholes are used as
    landfills.
92
Q

Effects of Subsidence and Soil Volume Change

soil volume changes

A

Causes billions of dollars is
damage annually to
highways, buildings, and
structures.

  • Swelling of expansive soils
    and frost heaving
  • Damage caused by soil volume
    change exceeds the cost of all
    other natural hazards
    combined.
93
Q

Effects of Subsidence and Soil Volume Change

salt mining

A
  • Coal mine structures have
    collapsed.
  • Water is used to dissolve
    and pump out salt, leaving
    behind cavities.
  • Flooding in salt mines can
    also cause sinkholes.
94
Q

Best solution is to avoid
building in vulnerable areas
through:

A
  • Geologic and soil mapping
  • Surface features
  • Subsurface surveys
    Subsidence and Sediments

Natural Hazards and Disasters (2 decks)

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