option D - geophysical hazards Flashcards
secondary hazards
- secondary effects of a natural hazard
- e.g: tsunamis, landslides, lahars
magnitude
size of a geophysical event
constructive boundary
- move away from each other; lava seeps through the crack to form new land
- e.g: south american and african plate (mid atlantic ridge)
destructive boundary
- subduction zone: denser plate subducts
- e.g: south american and nazca plate
transform boundary
- two plates that slide laterally against one another
- no volcanic activity
- e.g: san andreas fault
ring of fire
zone around the pacific ocean where volcanoes are most common
epicentre
- where the earthquake is felt the most on land
- directly above the focus
vulnerable population
infants, disabled and elderly people
focus
where the earthquake occurs deep in the ground
hot spots
thin areas in the earth’s crust where magma can escape
composite volcanoes
- along destructive plate margins
- pyramid shaped (has side vents)
- e.g: merapi, 2023
shield volcanoes
- along constructive plate margins (iceland) and where there are hot spots (hawaiian islands)
- dome shaped
- e.g: kilawea, hawaii
convection cells
slow motion of the earth’s solid rock by convection currents (surface dragged by friction)
human triggers - landslides
- lack of vegetation
- extraction of materials from the soil
cinder cone volcano
- cone shaped
- e.g: paracutin volcano, mexico
factors affecting slope stability
- gravity
- slope angle
- pore pressure
factors increasing shear stress
- removal of underlying support (undercutting, construction)
- transient stresses (earthquakes, mining)
earthquake case study
- haiti (near port-au-prince) –> 7.0 magnitude –> 2010
- 230,000 deaths
- 300,000 injured
- 1.5 million left homeless
- $8 billion in economic losses (over 100% of haiti’s GDP)
factors increasing vulnerability:
- poverty
- poor housing construction
- limited disaster preparedness
volcano case study
- eyjafjallajökull iceland 2010
- located on mid-atlantic ridge –> constructive plate boundary
- eruption was explosive, sending ash plume 10km high
- disruption to european air travel - over 100,000 flights cancelled affecting 10 million travelers
- 800 people evacuated from vicinity
landslide case study
- guinsaugon (philippines) –> 2006
- trigger: several weeks of heavy rainfall
- estimated 1,000-1,500 deaths
- 300 homes destroyed
factors increasing vulnerability:
- lack of warning systems
- poverty and lack of education
- poor infrastructure
pre-event management strategies
- land-use zoning
- public education and awareness
- improved building codes + construction
- early warning systems
post-event management strategies
- providing emergency shelter, food, water, and medical aid
- temporary housing solutions
- monitoring for secondary hazards
