physical geography - hazards

what is a geophysical hazard

sinkholes and eqs

what is a atmospheric hazard

tornado lightning cyclones

what is a hydrological hazard

flooding

what is a hazard

is a threat with the potential to cause harm / damage

what is a distaster

is a realisation of a hazard

what is vulnerability

the potential for loss

reasons people might be more vulnerable

physical economic social

natural hazard + vulnerability =?

risk of a disaster

characteristics of a hazard

clear origins and effect

little to konwarning

involentry exposure to risk

characteristic human responses to hazards

acceptance domination adaptation

what is domination

hazards r predictable and know what is going to happen

stages of the hazard management

PREDISASTER

1.identify and understand risk

2.analyse risk

3. prioritize

4. impliment risk reduction plan

5. raise public awarness

6. develop communication stratergy

DURING DISASTER

7.react to risk

8.treat risk

POST DISASTER

9. reconstruct and recover

10.monitor and review the process

contiantal plates

lighter

thick (30-70 km

av density 2.7g/cm3

old 1.5 mill years

made of silicon and alluminum

mainly granite

oceanic plates

dense

thin 6-10 km

av density 3 g/cm3

young less than 200 mill years

made of silicon and magnesium ]#

mainly basalt

earths heat produced from

primordial heat

radiogenic heat

what is primordial heat

Heat left over from the earths formation

What is radiogenic heat?

- Produced by the radioactive decay of isotopes

- Particularly...

- Uranium-238

- Thorium-232

- Potassium-40

layers of the earth

inner core,

outer core,

lower mantle, mesosphere

upper mantle, asthenosphere

crust, lithosphere

what happens in the asthenosphere

convection currents

what state is the inner and outer core in

inner: solid

outer: liquid

what state is the mesosphere and asthenosphere in

mesosphere: solid

asthenosphere: liquid

Evidence for Continental Drift

1) continental fit, 2) similarity of fossil plants and animals, 3) similarity of rock sequences

Paleomagnetism (sea floor speading)

north and south switch

magnetic crystals (magnitite) move around freely but as the rock solidifies the magnitite alines with the direction of magnetic north so u can see what the magnetic north was at the time it was formed

this can indicate what age/era the rock was formed

sea-floor spreading

it shows the age and polarity in semetrical lines eminating from the ridge

this indicates the rock are moving away from eachother

the plates move apart and magma rises and solidifies and creates new sea floor

the moho discontinuity

boundary between crust and mantle where siesmic waves change velocity

examples of constructive plates

euraisin plate

north american plate

destructive plate examples

indo-austrailian plate

pacific plate

conservitive plate examples

euraisian plate

african plate

hot spot volcanoes

volcanos move bc the plate moves creating new hot spot volcanos as the previous volcanos go dormant as the magma no longer rises

What is a rift valley?

-constructive plates move apart and magma rises thru the gap this causes the the gap to be filled in and widen,

-the streaching of the crust causes it to fracture in parallel faults

-the land between the faults collapse into large wide valleys --this continues and the rock falls beneath sea level creating new ocean

What is a deep sea trench?

oceanic and conenental and oceanic crust in desructive plate margins subduct forming a very deep part of the ocean

what r island arcs

in subduction the oeanic plate is melted due to the friction and hotter surroundings. this material is less dense than the surrounding asthenosphere and rises to the surface to cool and make ofshore composite volcanos

what r young fold mountins

mountines made by constructive plate margins going up

this movement causes eqs

what is gravitational sliding?

boyant magma rises up pushing plates apart and is hotter bc magma is hotter and lighter this is ridge push

the cooler heavier side of the plate is pulled down bc its heavier and therefore more effected my gravity this is slab pull

Conservative plate margin

-go either oppsosite ways or the same way different speeds

-have powerfull shallow focused eqs which r more devestating as they r closer to the surface and therefore population

-no magma or molten rock so no volcanoes

San Andreas Fault

is conservative plate margin

california has the 6th richest economy

land either side is heavily fractured fro secondary faults

pacific plate moves 6cm NW yearly

north american plates move 1 cm NW yearly

magma plumes

hot spots generated hotter temps in the lower mantle creating localised current making magma plumes rise verticaly

usualy found near plate margins

magma plumes can rise in the center of plates and 'burn' through the lithosphere to create volcanic activity on the surface

what are hot spots (in relation to magma plumes)

radioactive decay in the earths core generates very hot temperatures. if the decay is concentrated

, hot spots will form around the core heating the lower mantle

how to measure magnitude

Volcano Explosivity Index (VEI)

Volcano Explosivity Index (VEI)

0-8, magnitude of eruption

1-gentil

4-cataclysmic

8- mega collosal

name the types of explosion

icelandic

hawaiian

strombolian

vulcanian

vesuvian

peleean

plinian

predicting volanoes

little to no warning

eruption follows weeks of seismic activity

lahars (mudflows)

flows of ash, cinder, soil and rock that has been mixed i spring water and melted snow that then flow down the volcano

ocean ridges

plates move apart and magma rises to the surface, cooling and forms new crust

basaltic lava

volcanoes have gentle sides and infrequent eruptions

hot spots

created by magma plumes

creates mountin chains

subduction zone

where one plate moves under another

oceanic place melts and is less dense so it rises and erupts to form volcanos

danger of volcanoes depend on

location

population

magnitude/intenisity

ecomony

frequency

basaltic lava

runny (low viscosity)

quick

low sillica content

gass and steam escape quickly

shied volcanoes

constructive plate margins

andisitic and rhyolitic lava

viscous

high silica content

slower

gas and steam struggles to eascape

violent eruptions

composite volcanos

primary impacts of volcanic events

pyroclastic flow

lava flow

lahars

tephra

ash

tephra

rock fragments and particles ejected by a volcanic eruption.

pyroclastic flow

ash cloud on top

pick up material

layer of gas underneath acts as a lubricant allowing the ash to act as a liquid

seconday impacts of volcanic events

climate change

volcano case studies

- E15 2010

- Montserrat 1995

link between magnitude and frequency

the higher the mag the less frequent

intra-plate eq

in the middle of the plate away from the boundary

inter plate boundary eq

at the plate boundery

human causes if seismicity

fracking, mining, drilling, contruction of dams and reseviours

can explain intra eqs

focus

where the rock fractures/ where the eq eminates from

epicenter

Point on Earth's surface virticaly above an earthquake's focus

4 types of waves

P (primary)

S (secondary)

R (rayleigh)

L (love)

p- waves

A type of seismic wave that compresses and expands the ground.

longitudinal wave

high frequency

fasted- reach the surface first

travel thru the mantel and core (opposite side of the earth)

s-waves

A type of seismic wave that moves the ground up and down

transverse waves

travels thru the mantel but not core

2 surface waves

Love waves and Rayleigh waves

L-waves (love waves)

move side to side on the surface

originates from the epicenter

cause the most damage

r-waves

radiate from epicenter and out

complicated low frequency rolling motions

up and down wave motion

l and r waves

most sevre to people and property

hard rock - absorbs surface waves so there is usualy less devisation

soft rock - rocks r like jelly so usually r more devistated (y costal areas r badly effected)

3 ways of measuring magnitude

richter scale

moment magnitude

modified mercalli scale (MMI)

Effect of rapid urbanisation eqs

more buildings can collapse and kill more people

easpecialy in slums (LICs and NEEs) due to low quality infrastructure

political impacts of Eqs

trust- more responce/ managment can decrease trust

changes in law/ legislation(building regs ect)

anything that changes the gov (politicans killed or loss of gov buildings )

liquefaction

shaking destabalises soil, the grains looses structure and water floods the gaps making it waterlogged and flow like liquid/mud

flows like quick sand

buildings and cars sink

case studies eqs

haiti

boxing day tsunami

monitoring areas at risk

- use satilitte surveying/ remote sensing

- radon gas sensor

- water table level

- strain meter

- laser reflector

- levelling

- seisometer

- gravity meter, magnetometer, and electrical resistitivity meter

predicting seismic hazards

- very difficult to predict

- seismic gap theory

- hazard mapping

protection against seismic hazards

- aseismic desighn

- retrofitting

- apropriate technology

- land use planning

- fire prevention

modify human behaviuors eqs

- education

- responce of emergency services

- risk shaing and community preparedness

- modifing loss by insurance and aid

tropical storm

an intense low pressure system that develops in the tropics

an atmospheric disterbance

spacial setting Tropical storm

most hurricanes occur in the tropics of capircorn and cancer

from 5-30 degrees N or S of the equator

they move westwards then north

temoral setting tropical storm

- most hurricanes occur from spring to november and som einto dec/jan

- 6 months apart in the N&S hems

- not evenly distributed 33% east asia and 11% carribean

How do tropical storms form?

sea temp above 26.5 degrees

need a cluster of thunderstorms then needs the coriolis effect to it rotates

need low pressure

needs low vertical windsheer so it doesnt tear the storm apart

coriolis effect

The effect of Earth's rotation

the coriolis effect causes winds to veer right in the north hem and left in the south hem

characteristic of hurricanes

200-700 km in diameter

intense area of low pressure

rotating wind system

moves E before moving NorS

travel 20km/h depending on latitude

symetrical around the eye

eye wall most destructive

life span 7-14 days

return period

is the return at which a certain intensity of a hurricane can be given within a 100km raduis of location

Dissipation of tropical storms

7-14 days long

caused by loosing energy when the latent heat provided by condenation is cut off eg when it moves over colder water or land

factprs effecting vunerability for tropical storms

- speed of movement

- distance from the sea

- physical geography of the costal area(width of coast plane)

- preperation

- warnings and community response

storm surge

winds push water over the shore line

can go 6 meters above sea level and go for 100km

bc its a low pressure zone the water is pushed along and above like a wall instead of a wave that breaks

prevention of tropical storms

is none really

prediction in tropical storms

-satellites monitoring and sea based recording centers

- pridicted path to prioritise evacuation (needs to be accurate bc evacuation is expensive) but they can have a eratic path so predition is difficult and cannot give more then 12- 18 hours warning

protection in tropical storms

- evacuation

- national gaurd to prevent looting

- advice on strenghtening homes

- hurricane drills

- land-use planning

- sea walls- break water and flood barriers

- retrofitting adjust buildings to withstand wind

Quasi-Natural Hazards

occurs when humans interact with natural processes

what % od wildfires are caused by hamans vs natural

human- 10% (eg ciggrattes campfires arson and agricultural fires)

natural- 90%

fire triangle

ingition source

feul

oxygen

flame front

when the wind extend the flame further to burn ahead

fire brand

a piece of burning material that gets blown a distance to create a new fire

embers

flurring debris coming from the fire

spot fires

Projections of flaming or burning particles (fire-brands) that are found ahead of the flame front creating new fires

Pre-heating

- when the fire heats up the litter ahead of it so the fire continues quicker (gets rid of moisture)

ladder effect

when the fire goes from the ground to low leing leaves and branches that then climb to the crown of trees

relative humidity

level of moisture in the air

convection columns

virtical rise in heat smoke ash ect