hazards Flashcards
describe the processes at constructive plate boundaries
At constructive plate boundaries, convection currents cause two oceanic plates to move apart, thus enlarging the rift between them. Material from the mantle rises and forms magma due to the fall in pressure. Magma continues to rise through the rift and can cause minor volcanic flows, submarine volcanos, or minor earthquakes.
describe the processes at destructive plate boundaries?
Convection currents cause oceanic and continental plates to move close together at destructive boundaries. The oceanic plate, being denser than the continental plate, subducts under the continental plate due to slab pull which is the gravitational force generated by its own weight exerted on the oceanic plate. At the boundary between the two plates, a deep ocean trench forms. Meanwhile, water seeps through the cracks of the mantle wedge of the subducting plate, thus lowering the melting point of the rock. The mantle wedge melts, turns into magma, and rises to the surface, where powerful volcanic eruptions can occur.
describe the processes at destructive plate boundaries?
Convection currents cause oceanic and continental plates to move close together at destructive boundaries. The oceanic plate, being denser than the continental plate, subducts under the continental plate due to slab pull which is the gravitational force generated by its own weight exerted on the oceanic plate. At the boundary between the two plates, a deep ocean trench forms. Meanwhile, water seeps through the cracks of the mantle wedge of the subducting plate, thus lowering the melting point of the rock. The mantle wedge melts, turns into magma, and rises to the surface, where powerful volcanic eruptions can occur.
define natural hazard
A physical event that endangers life and property
tectonic hazard: Earthquake, Volcanic eruption, Tsunamis
atmospheric hazard: drought, Tropical Storm, Tornado
land hazard: landslide, rockfall, avalanche
bio hazard: forest fire, disease outbreak, locust plague
factors affecting hazard risk
Magnitude – the scale of the hazard is very important
Frequency – How often hazards occur impact the level of risk
Proximity to hazard – Hazards that occur close to human activity have greater risk
Population density – The number of people exposed to the hazard greatly affects risk
Nature of secondary hazards – some hazard result in more dangerous secondary hazards. E.g. tsunamis
describe processes occurring at conservative plate boundaries
two plates slides past each other. Friction between the two plates builds stress in the fault producing frequent earthquakes. One example is San Andreas fault
define plat theory
theory that the Earth’s crust is divided into several plates that glide over the mantle, the rocky inner layer above the core. These plates interact with each other to form landforms and create hazards
earthquake distribution?
These are located mainly at plate boundaries – the points where plates meet or separate. The most frequent earthquakes occur at conservative plate boundaries. The most powerful earthquakes occur at destructive plate boundaries. Earthquakes also occur in large plate boundary zones and at micro-faults.
volcanic eruption distribution?
occur at constructive plate boundaries where plates move apart. Here shield volcanoes have low magnitude high frequency eruptions.
Destructive plate boundaries feature more explosive, low frequency eruptions from composite volcanoes. Volcanoes also erupt at hotspots that feature mantle plumes. For example Hawaii
define primary and secondary effect
Primary effects are directly caused by the hazard.
secondary effects are an indirect consequence of the hazard, such as earthquake lead to landslides and tsunamis. Eruptions lead to forest fires, floods and grounded planes.
examples of primary and secondary effects
For earthquakes: primary - ground shaking causes buildings to collapse, injury and death
secondary - landslides, tsunamis
for volcanic eruptions: primary - ash fall and pyroclastic leads to damage to the environment, injury and death
secondary - forest fires, floods and grounded planes.
define immediate and long-term responses
immediate: Search and rescue
Short term aid – shelter, first aid, food and water
long-term: Rebuilding and reconstruction
Reducing future risk
Financing livelihoods, recovery of economy
Using named examples explain how the
effects and responses to a tectonic hazard
are different between a rich country and a
poor country
The effects and responses to tectonic hazards compare saliently between the 2014 Nepal earthquake and the eathquake that took place in italy in 2016
