Hazardous Environments Flashcards
What is a hazard
An extreme event that threatens people, their property and settlements
When does a hazard become a disaster
When the hazard causes widespread destruction to property and human lives(death)
Risk
The probability of an event happening and the scale of its possible damage
Features of oceanic crust
-newer(less than 200 million years old
-denser(heavier)
-thinner(5km)
-can subduct
Features of continental crust
-older(1500million years old)
-less dense
-thick(30 km)
-cannot subduct
Ways tectonic plates move
-slab pull
-ridge push
-convection currents
Lithosphere
Top 100 km of the earth that makes up the earths tectonic plates
Asthenosphere
The rest of the upper part of the mantle that acts as a lubricant for the tectonic plates to move on
Trends in the distribution of earthquakes and volcanoes
-mostly correlate with plate boundaries
-volcanoes are three quarters around the pacific ring of fire which is a ring around the pacific
Volcanoes that aren’t on plate boundaries are called hotspot volcanoes
Features of constructive plate boundaries
-2 plates move apart, creating new crust in the middle as magma pushes its way up and solidifies
-creates effusive volcanoes and small earthquakes
Features of destructive plate boundaries
-two plates move towards each othee
-oceanic plate subducts underneath continental plate
-subducting plate melts because of high temps in the earth. Magma rises and is extruded at the surface, forming volcanoes
-creates powerful earthquakes and explosive volcanoes
Collision plate boundaries
-2 continental plates collide
–forced to buckle upwards
-causes powerful earthquakes and fold mountains. No volcanoes
Conservative plate boundaires
-2 plates slide past each other
-creates powerful earthquakes as pressure builds up between the plates then is suddenly released
How does a volcano form at a constructive boundary
-two plates move apart from each other
-magma rises to the surface at this weak spot and is extruded in eruptions
-this forms volcanoes when it solidifies to lava
-forms shield volcanoes
-also forms new land
Characteristics of shield volcanoes
Short
Gently sloping
Composed of basaltic lava
Low viscosity
Effusive eruptions
destructive boundary volcano formation
-two tectonic plates converge together
-oceanic plate subducts underneath continental plate
-oceanic plate melts
-newly formed magma rises to the surface and is erupted
-forms a volcano over time as more material is erupted, cools and solidifies to lava
-forms strato volcanoes
characteristics of strato volcanoes
-tall, steep-sided
-alternating layers of lava and pyroclastic flow/ash deposits due to sticky, high viscosity rhyolitic lava which have explosive eruptions
benefits of living near volcanoes
-jobs created(tour guides, mining
-fertile soil for farming
-geothermal energy can be used to heat homes
-valuable minerals
-tourist visit to see features like geysers, bringing money to the economy
-can create new land
negative of living near volcanoes
-risk of eruption
-risk of contaminated water
-mining can cause noise, air and dust pollution
-ash can have negative impacts on infrastructure
-destroy land during eruptions
-poisonous gases and ash erupted that are harmful and contaminate the air
why do people live in areas at risk of earthquakes
-ignorance of the risk-may not have a large earthquake in living memory
-no social memory of an earthquake having occurred
-wish to stay near relatives/where they grew up/god location etc
-people do nothing and accept the hazard
-people adjust to living in a hazardous environment (strengthening the home and preparedness)
causes of earthquakes
-plates get stuck due to friction, often caused by protrusions on the opposite plate
-pressure builds up
-pressure gets too great and plates slip. Slipping motion causes energy to be released in the form of seismic waves, which is an earthquake
precursor events of earthquakes
small tremors in preceding months
increase in radon emissions
-indicators of previous earthquakes(fault lines and seismic gaps)
Factors affecting number of deaths
-age of building/if they have been made EQ proof
-infrastructure damage
-potential for ground liquefaction
-population density
-poverty
-poor governance
-depth of focus
-strength of earthquakes
-number of aftershocks
-level of development
-time of day
-distance from epicentre
-proximity to secondary hazards(tsunamis, landslides etc)
locations of tropical cyclones
-tropical oceans 5-30 degrees N/S o the equator
-hurricanes in the Atlantic and eastern Pacific oceans
-cyclones in the Indian Ocean
-Typhoons in the western Pacific