TECTONICS Flashcards
what is a natural hazard
naturally occurring event with the potential to cause loss of life/property.
what is a natural disaster
when the natural hazard causes social, economic and environmental damage.
vulnerability
people’s ability to cope with hazard events
what does vulnerability depend on
how exposed to the hazard the population is. how susceptible to human and/or economic loss because of where they live
case study Nepalese earthquake
- date= 25 April 2015
- magnitude=7.8
- half its population living in poverty
- infrastructure severely damaged(not built to withstand natural disaster)
- is mountainous= many landslides=rescue is difficult
- emergency services unable to cope
- tourism fell=unemployment
deggs disaster model
overlap of hazard and vulnerability causing disaster
constructive/divergent plate boundaries
plates moves apart forming new crust
mid ocean ridges
an elevated region with a central valley on an ocean floor at the boundary between two diverging tectonic plates where new crust forms from upwelling magma.
rift valleys
A rift valley is a lowland region that forms where Earth’s tectonic plates move apart, or rift. Rift valleys are found both on land and at the bottom of the ocean, where they are created by the process of seafloor spreading. where the land between two continental/oceanic plates collapses.
destructive/convergent plate boundaries
plates move towards each other where the lighter /less dense plate subducts
subduction
the movement of the less dense plate sliding under the denser plate
oceanic plates are usually more denser than continental plates
oceanic plate-continental plate
oceanic plate subducts creating fold mountains, where plate collision forms folding.
constant movement=continuous folding=increase friction in Benioff zone. magma pushes through gapes creating explosive volcanic eruptions
oceanic plate-oceanic plate
lighter plate subducts, deep ocean trenches and volcanoes form. submarine volcanoes grow to form island volcanoes(island arcs).
shallow deep focus earthquakes occur
Benioff zone
area where friction is created between colliding tectonic plates , resulting in intermediate and deep earthquakes
continental-continental
collision margin occurs forcing rock upwards forming high mountains e.g Himalayas. =no volcanic activity and earthquakes are shallow focus
conservative boundaries
2 plates slide past each other.(move parallel towards each other in opposite directions.)form transform fault. no volcanic activity. friction creates powerful earthquakes . at points where plates get stuck to each other stress is built up. the longer the stress is built up the greater the magnitude of the earthquake.
Collison margin
If two continental plates collide, neither can sink and so the land buckles upwards to form fold mountains. This is called a collision margin.
How are earthquakes caused
formed along plate boundaries
friction between plates causes pressure to build up release of this stress/pressure causes earthquakes at different magnitudes
explain and name the 3 types of seismic waves
- P WAVES(primary)= are the fastes waves, move through solid and liquid. moves forwards and backwards creating expansions and compressions. least damaging
- S WAVES(secondary)= moves slower than p waves. moves through solids only. moves in a sideways motion at right angles to direction of travel. more damaging than p waves.
- L WAVES(love)= moves slowest. last to arrive. Shake ground side to side . most damaging. are larger. and focus most of its energy onto earths surface.
what are seismic waves measured by
seismometer
primary impacts of earthquakes
- crustal fracture
- building / infrastructure collapse/damage
- ground shaking
secondary impacts of earthquakes
- liquefaction, surface of rocks acts more like a liquid than solid during movement, causing building + roads to sink +power and gas lines to break causes fires.
- Landslides/avalanches,
- tsunami-cause coastal flooding
loma prieto earthquake -case study
date-17 October 1989 magnitude- 6.9 location- san Francisco -Loma Prieto built on soft sand- liquiefaction-buildings and roads collapsed caused 42-67 earthquake related deaths
aftershocks of eartyhquakes
larger earthquakes= more aftershocks
cause more damage to building structure= more possible death=more economic environmental damage.
Aftershocks are smaller earthquakes that occur in the same general area during the days to years following a larger event or “mainshock.”
measuring earthquakes
magnitude- is energy release by epicentre. MMS measures energy released by earthquake. using information on- seismic waves, rock movement, fault surface broken by earthquake and resistance to rocks affected
scale= 1(small)-10
- intensity = impact of earthquake on people MMIS(modifies Mercalli intensity scale= I(hardly noticed) - XII(catastrophic)
earthquake prediction
no accurate method, relies on forecasting and researching foreshocks, although not reliable.
Causes of volcanic eruptions
as plates moves pressure builds up and hot magma rises above through crust. as lava cools rock forms- so volcanoes grow as they erupt.
primary hazard of volcanoes
- lava flows
- pyroclastic flow- fast moving destructive mix of dense hot ash gas and rock from a volcano-v. dangerous
- ash and tephra falls- ash blasted from eruptions, destructive , can injure or kill, travel thousands of km, case poor visibility and slippery roads.
- gas eruptions-dissolved gasses released during an eruption-water vapour, CO2 and SO2, travel huge distances.
Secondary hazard of volcanoes.
- lahars-flows of mud, water and rock -form when heavy rainfall during eruptions erodes loose rock and soil or eruptions melt snow/ ice
- jokulhlaups- when volcanic eruptions melt part of glaciers. the sudden release of gravel water and ice is v. dangerous.
measuring volcanic eruptions
volcanic explosivity index- VEI
0(non-explosive)-8
based on volume of tephra, height of material ejected into atmosphere, duration, observations
predicting volcanoes
using gps, seisometers and satallite bases radar. are not 100%accurate
hotspots
A hot spot is an area on Earth over a mantle plume or an area under the rocky outer layer of Earth, called the crust, where magma is hotter than surrounding magma. The magma plume causes melting and thinning of the rocky crust and widespread volcanic activity
impacts of tsunami
-damage to infrastructure
-travel for miles inland
-change landscape, more severely on small islands.
-drowning/injuries/death
secondary hazards-
famine
disease outbreak
homelessness
economic damage
damage to ecosystems
predicting tsunami
little way of predicting,
seismic sensors used to detect undersea earthquakes as well as DART(deep ocean assessment and reporting of tsunami.
causes of tsunami
earthquake underwater, causes the displaced of water in sea. the length of wave increases when closer to land. the size of earthquake and the proximity to land determines the length of wave
length of wave can range from 1 meter to 30 meters etc.
Indian ocean tsunami- case study
date- 26 december 2004 magnitude-9.0-9.3 indian ocean plate lifted 15 metres proximety-17 metres low lying coastland- cased the wave to travel very far inland social: 5 million people affected 230 000 death as well as 9000 tourists 1.7 million left homeless 70% of people in villages dead no early warning system 14 countries affected environmental: ecosystems such as mangroves and coral reef damaged economic: water supplies contaminated by salt water total cost- $10 billion
Iceland Eyjafjallajökull erupts- case study
date- april 2010 location iceland ash cliouds affected flights 100 000 flights cancelled affected 10 million people economy in kenya fell due to no exportations on green flowers
hazard risk formula
capacity
political factors affecting risk from natural hazards
- building codes and regulations
- quality of infrastructure
- preparedness plans
- efficiency of emergency services
- quality of communication systems
- public education and practice of hazard response
- extent of government corruption
economic and social factors affecting risk from natural hazards
- level of wealth(peoples ability to protect themselves and recover from a hazard)
- access to education
- quality of housing
- quality of healthcare
- income opportunities
physical and environmental factors affecting risk from natural hazards
- density of population
- speed of urbanisation
- accessibility of an area
haiti-developing country-case study
date-12 January 2010
magnitude 7.0
shallow focus
liquefaction causing building sink.
epicentre only 24km to capital Port-au-Prince
-is poor countrry, not enough resources for earthquake preperation
high levels government corruption therefore reduced living standards and poor infrastructure=lack of regulations
-rescue =difficult = g=high population density
-not many people knew what to do because of low preparedness for disaster.
roads destroyed so aid could not come in as fast.
destroyed building- recovery and relief difficult.
cholera outbreak lasted 6 years- 720 000 affected.
Haitis recovery- case study continued
-many officials dead, NGO needed for emergency services,
-corruptions= other countries unwilling to give aid.
80 000 people in temporary housing
in 2015:
-new buildings, roads& schools built
-health statistics improved
-stronger government
China -emerging country- case study
date 12 may 2008
magnitude-7.9
45.5 million people affected
5million homeless
many injuries, high economic cost
poor building regulations
fewer deaths since the earthquake was rural
is wealthier than Haiti-afford rescue missions
people at risk from landslides relocated
within only 2 weeks temp homes and roads where built.
99%of destroyed farmland rebuilt.
japan-developed country- case study
date- 11 march 2011 magnitude 9.0 fukishima nuclear power plant destroyed-47 000 people evacuated had fewer deaths than Haiti and china -strict building regulations -low levels of corruption -earthquake education with frequent practise drills in schools and businesses - disaster plane: -10 meter high tsunami walls -evacuation shelters -marked evacuation routes -earthquake emergency kit. -early warning system response: all radio and tv live broadcast 110 000 defence troops immediately mobilised received aid from 20 countries only negative was the plant hadn't been built to withstand tsunami.
hazard profiles
show characteristics of hazards and help show ways of different events may be compared
multiple hazard zone
countries exposed to multiple hazards; need aid from other countries to plan disaster prevention
Philippines; multiple hazard zone- case study
7107 islands
101 million people
25%pop lives in poverty
mostly mountainous with coastal lowlands
volcanoes- located in the ring of fire
tsunami- coasts face the pacific which is the most tsunami-prone area
typhoons- sits within the typhoon belt
deforestation makes landslides common
vulnerability:
economic development led to rapid urbanisation=high pop density
poor live in coasts and exposed to storm surges
2006 earthquake- killed 15, damaged 800 buildings and 3-meter tsunami
describe the 4 stages in hazard management
1) mitigation; reduce loos of life and damage to infrastructure and environment- plan land use, building regulations and defenses
2) preparedness; minimize loss of life and property-early warning systems, organise evacuations, raise awareness
3) response; aim to save lives and protect property- rescue/search/evacuate, restore infrastructure, medical care
4) recovery; short-term; immediate needs- medidocal care, transport, food water, temp housing. long term;reduce vulnerability- rebuild homes schools and infrastructure.
park hazard response curve
can be used to asses/cpompare how well places respond after a hazard event
hazard mitigation strategies
- land use zoning
- diverting lava flows
- GIS mapping
- hazard resistant design and engineering defences such as sloped roofs on houses near volcanoes to reduce ash build up and collapse
hazard adaptation startegies
- high tech monitoring; GIS, mobile phone, early warning system, satellites
- crisis mapping
- modeling hazard impact
- public education
list 2 key players managing loss
-AID DONORS;
clean water , food, reconstructing buldings
-NGO
provoide funds, search and rescue assist in building schools and medical centers.
