Natural Disasters Exam 2 PITT

shoaling

process of wave height increase and breaking

-KE-PE

-occurs further from land

Tsunami Damage (depends on):

-size of the event

-offshore bathymetry

-distance of coast from triggering event

-coastal geomorphology

-coastal orientation

-state of the tides at the time of the tsunami

offshore bathymetry

shoaling can occur in different locations or sooner/later

coastal geomorphology

irregular coastline can concentrate wave energy

monitoring(tsunamis)

technology intensive

-PTWC

-estimates time and speed

NOAA's DART system

Deep-Ocean Assessment and Reporting of Tsunamis,

- bottom pressure recorders detect crest of tsunami,

-information transmitted to surface buoys that relay to stations via satellite

Which state has the highest risk rate for tsunami?

Hawaii

-center of the pacific

-vulnerable form every direction

Volcano

Manifestation at the surface by the release of a solid/liquid/gas due to internal heat processes

two prerequisites for volcanic activity

-something to melt

-source of heat

not all volcanoes like Hawaii

average global production of lava

2 km3 per year

Types of volcanoes

-water/steam eruptions(hot springs and geysers)

-carbonate magmas(Ol Doinyo Lenngai volcano)

-explosive volcanoes(Pinatubo volcano, Phillipines)

Are volcanoes a source of heat?

Yes.

thermal energy being dissapated in the form of heat loss(convection,conduction,radiation)

heat of fusion

Amount of energy required to change a substance from the solid phase to the liquid phase.

most common volatile species

H20, CO2, SO2, CO, H2S

Properties of Volatiles

At high pressure volatiles are in solution hence-lower viscocity

-example:Coke bubbles

-Low molecular weight so much larger volume

Viscocity

internal resistance or strain by a substance when subjected to a shearing(stress)

-Sluggishness of a fluid

Factors that affect viscocity

-temperature

-phenocryst

-bubble content

-volatile content

-sulfer content

-pressure

-increase of Silica=increase in viscocity

Lava Types/Composition

-basaltic composition

-andesitic composition

-rhyolitic composition

basaltic composition

-dark igneous rock with small grains

-partial melting of upper mantle

-in general same as terrestial composition

-shield shape volcanoes

andesitic composition

-lava production at subduction zones

-fluids enter overlying mantle

-melting if H20 lowers melting point

-cone shape or composite volcanoes

Hydrous(wet magma)

at 90 km depth 20 percent h20 is soluble

forms composite or cone shaped volcanoes

rhyolitic composition

-very high silica(very viscous)

-sticky wet magma

-very explosive

-thick flows

Eruption Types

-Surtseyan

-Hawaiian

-Strombolian

-Pilinian(Ultra)

-Pelean

Hawaiin eruption

-small explosive activity

-low eruption columns

-spatter and cinder cones

-typically basalt

Strombolian eruption

-low coulumns more energetic than Hawaiin

-Cones and sheets

-basalt or andesite

-example: Helka, iceland 1970

Pelean Eruption

Collapse of lava dome

pyroclastic flows

-example:Mt. Pelee,1902

Surtseyan Eruption

-violent explosions due to contact with seawater

-low steam coulmns

-cone ring

-high fragmented ash

-example: Surtsey (Ireland)1965

Pilinian eruption

-high coulmns

-powerful sustained eruption

-large pyroclatic sheets

-example: Vesuvius

Types of volcanic precursors

-seismic

-deformation

-heat discharge

-gas discharge

-water flows

seismic monitoring

-network or seismometers used to measure magnitude, frequency, and distribution

-high frequency EQ's lead to eruptions

Volcanic tremor

-caused by magma movement in the conduit

-gas bubble formation

-causes long period EQ's

Seismic zone

-region of no earthquakes

-defines magma storage

What does volcanic tremor activity tell us?

Warns us of magma rising and impending eruptions

Deformation

-measurement of change sin volcanoes shape due to increasing pressures

tilt meters

-sensitive water tubes meters long

-detect changes in slope

-old technique

laser sighting(volcanoes)

-precise movements of the distance between a laser and a target

heat flow warnings(volcanoes)

-volcanoes begin to heat up weeks before

-soil and groundwater affected

-direct and indirect measurement

volcanic gas monitoring

-chemistry of gas is used to determine composition of magma

where do volcanoes emit gas from?

-lakes, fumaroles, soil, vents

How are volcanoes mitigated?

-Lava diversion:

-water cooling

-lahar diversion

-public education

7 primary volcanic hazards

-ash falls

-hot ash flows

-mudflows(lahars)

-volcanic landslides

-lava flows

-volcanic tsunamis

-poisonous gas

landslide

a slide of a large mass of dirt and rock down a mountain or cliff

-rock,soil,ice,snow

Factors of landslides

-gravity

-human impact

-water

-strength of ground

What initiates Landslides?

-Saturation by water

-freeze and thaw cycles

-erosion and steepening of slopes

-earthquakes

-eruptions

-vibrations

-loading(weight on top)

Types of landslides

slumps, slides, rockfall, flows

Fall Landslide

-material moves through air

rapid process

example:rock-fall

Slide Landslide

-blocks of material

no internal shearing

-types: rockslide, slump, landslide

Slump landslide

-sliding of material along curved surface

-common in sediments or weak rocks

Flow Landslides

-material breaks up and moves like fluid

-high viscocity at syrface

Flow landslide types

-creep:slow movement of soil

-initiated: freeze thaw cycle or wetting and drying

-debris avalanche

Susceptibility

-probable degree or response of rocks and soils to natural or artiificial cutting

How do we predict landslides?

-oversteepened slopes

-geology and structure; weak bases or prior falls

-water buildup

-vegetation

Landslide Mititagtion

-slope drainage

-perforated pipe

-wells in slopes

-slope reduction

-retaining walls

Heat wave

Short period of heat

-days to weeks

Drought or Desertification

Long period of heat, lack of water, crop failure

-months to years

what is a desert?

-region with less than 25 cm per year with little vegetation

-1/3 of earth is desert

how do deserts form?

-regions with high evaporation

-warm, dry air masses

-cold air sinks with verlying atmosphere

Types of deserts

-polar

-mid-lattitude

-trade-wind

-coastal

Polar Desert

-area of intense cold and very little snow

-example: Antartica

Mid Latitude Desert

-basins of large continental land masses

-low rainfall and sparse vegetation

-example: Gobi Desert

Trade wind desert

-located at 30 degrees N and S latitude

-controlled by sinking air masses

-very arid

-example:Sahara Desert

Coastal Desert

-western edges of continenet

-bounded by cold ocean currents

-example: Peru, Nambian Desert

Climate Regimes

-Hyper arid

-Arid

-Semi-Arid

Hyper Arid regime

receive less than 2.5 cm of rain

Arid Regime

-recieves 2.5-25 cm of preicipitation

-marked by drought resistant vegetation

-saline lakes in areas

-example: Kalahari Desert

Semi-Arid Regime

-receive 25-50 cm of precipitation a year

-marked by semi stable vegetation and sparse agriculture

-margins of larger desert systems

process of desertification

slowly advancing of desert conditions along a desert edge

causes of desertification

-climate change

-land degradation/soil erosion

Climate change(desertification)

-short term climate chnage causing periods of dryness

-drought does not equal desert

-can lead to famine

Land degradation/soil erosion

-human land use patterns which lead to desert conditions

-over cultivation and over grazing

-deforestation

-bad immigration practices

What is the most damaging and costly hazards?

weather hazards

Why is the U.S important to weather hazards?

-highest number of tornadoes

-second highest number of lightning strikes

-only country to have large nor'easters

Thunderstorms

-bring heavy rain

-flash flooding, strong winds, hail, and lightning

-1,800 ongoing at any one time

How are thunderstorms formed?

-combination of moisture, rapidly rising warm air

-force capable of lifting air

-warm and cold front

How do Thunderstorms appear?

-dark

-single, cluster, or in lines

-affect several locations in course of hours

-all contain lightning

what is a multi-cell storm?

-each rain cell is a region of intense updraft

-followed by heavy rains

-drafts can force upodrafts of warm moist air

Supercell thunderstorm characteristic

-largest strongest and longest lasting thunderstorms

-capable of producing tornadoes

-air speeds up to 170 mph

How do you monitor thunderstorms?

-local: news and weather centers

-Nationally:use of satellites

example:national weather service

-watch the skies and take shelter

Doppler Radar

-device that sends out radio waves used to measure weather

-objects like snow, rain, and hail bounce back waves

-measure frequency change

How many bolts of lightning hit the earth every minute?

-6000 bolts

Lightning characteristics

-split trees and cause fires

-kill more people than tornadoes and hurricanes

-3-4 miles long and 1 inch wide

-hotter than surface of sun

What is lightning?

-electrical discharge that results from buildup of positive and negative charges in thunderstorm

-likely result of collision pf ice crystals

what causes thunder?

Rapid heating and cooling of air

what percent of lightning actually strikes?

20%

what percent of lightning victims die?

25%

-others suffer organ damage

Two prime factors to tornado initiation

-topography

-local climate

Where is tornado alley?

-Texas, Oklahoma, Kansas, Iowa, Nebraska, Montana, Illinois

which state has the least tornadoes?

Alaska

Which state has the most tornadoes?

Texas

Tornado dimensions

-Width: 75 yards

-Track Length: 1-4 miles

-time on ground: 5 min

-Forward Speed: 25 mph

Prime season for tornadoes

-Spring-Summer

-late afternoon to late evening

Tornado Structure

Combo of opposing wind patterns

-higher level=dry/ cool winds from the west

-lower level=warm/wet winds from the east

What are large storms with multiple tornadoes called?

Families or Swarms

Which direction do tornadoes move in?

SW to NE

(Enhanced)Fujita scale

model scale used to describe tornado strength

-E0-E5

EF0 Tornado

65-85 mph winds

-light damage

EF1 Tornado

86-110 mph winds

-Moderate damage

EF2 Tornado

111-135 mph winds

-considerable damage

EF3 Tornado

136-165 mph winds

-severe damage

EF4 Tornado

166-200 mph winds

-Devastating damage