Hazardous Environments Flashcards
(46 cards)
Define hazards
An extreme that threatens people, their property and settlements
Define disaster
When a hazard causes widespread destruction to property and human lives
How hazardous or disastrous an event is also dependant on…
Risk - the probability of an event happening and scale of its possible damage;
The ability of a population to make adjustments or mitigation and their ability to cope;
How easy the hazards events are to predict;
The frequency of the event;
Some places may be in experience more that one hazard (eg Philippines);
The severity of the hazard.
Types of hazards
-geological (eg volcanic eruptions, earthquakes)
-climatic (eg tropical storms)
Outer core
- 2200km thick
- liquid
- 3000 C
Crust
- 0-70km thick
- continental and oceanic crust
- solid —> mainly granite and basalt
- 10 C
Mantle
- 2900km thick
- solid, but flows
- 375 C
Inner core
- 1270km thick
- solid —> mainly iron and nickel
- 3000 C
Oceanic crust
- newer (less than 200 millions years old)
- denser (heavier)
- thinner —> 5km
- can subduct (go under into mantle)
Continental crust
- older (1500 millions years old years old)
- less dense
- thick —> 30km
- can’t subduct
Lithosphere
Top 100km of the earth (ie crust and top part of the mantle) that makes up earth’s tectonic plates
Asthenosphere
The rest of the upper part of the mantle that acts as a lubricant for the tectonic plates to move on
How do tectonic plates move?
- slab pull
- ridge push
- convection currents
How does slab pull work?
Occurs when a dense oceanic plate sinks into the mantle at subduction zones. As it sinks, it pulls the rest of the plate along with it, creating movement
How does ridge push work?
At mid-ocean ridges, magma rises to form new crust. As this crust moves away from the ridge, it pushes the plates apart, causing them to move
How does convection currents work?
These are circular movements of molten rock in the earth’s mantle caused by heat from the core. Hot material rises, cools, and sinks, creating currents that drag the plates along the surface
Worldwide distribution of earthquakes and volcanoes
- uneven
- mostly correlate with plate boundaries
- earthquakes occur in linear chains along all types of plate boundary
- some earthquakes occur away from plate boundaries, this could be due to human activity like mining, fracking etc
- volcanoes also occur in a linear distribution, like around the pacific ring of fire, and are related to destructive plate boundaries
- other volcanoes are not on plate boundaries, called hotspot volcanoes, they occur where plumes of magma rises and meets the crust and form a chain of volcanoes eg Hawaii
Types of plate boundaries
- divergent aka constructive
- convergent aka destructive
- collision
- transform aka conservative
Divergent aka constructive plate boundary
- when 2 oceanic plates move apart
- creates effusive volcanoes and small earthquakes
- eg Mid Atlantic Ridge
Convergent aka destructive plate boundary
- when oceanic plate subduct underneath a continental plate
- creates powerful earthquakes and explosive volcanoes
- eg Nazca plate subduct under South American plate
Collision plate boundary
- when 2 continental plates collide
- causes powerful earthquakes and fold mountains
- eg Indian plate colliding with Eurasian plate and forming the Himalayas
Transform aka conservative plate boundary
- when 2 continental plates slide past each other
- creates powerful earthquakes
- eg Pacific plate and North American plate
Constructive plate boundary volcanoes formation
- Two plates move apart from each other (usually at mid-ocean ridge, though can also happen at a rift valley with 2 continental plates pulling apart).
- Magma rises to the surface at this weak spot and is extruded in eruptions, forming volcanoes when it solidifies to lava
- This leads to shield volcanoes
Destructive plate boundary volcano formation
- Oceanic plate subducts underneath continental plate
- Oceanic plate melts due to dehydration melting.
- Newly created magma rises to the surface and is erupted, forming a volcano over time as more material is erupted, cools, and solidifies to lava
- Creates strato volcanoes
