Earth And Natural Disaster Flashcards
Order of the 4 parts of the earth
- Crust
- Mantle
- Outer core
- Inner core
Crust
- thinnest layer
- only 8-65km thick
- made of less dense rock so floats on mantle
Mantle
- thickest part of earth
- 2900km thick + denser than crust
- upper mantle is rigid but lower mantle is semi-molten and has convection currents
Outer core
- 2200km thick
- made out of molten iron and nickel
Inner core
- made of solid iron and nickel
- densest layer of earth because is under immense amts of pressure
- 1260km thick
What 2 layers is the lithosphere made of?
Crust + upper mantle
Constructive margin
- plates diverge (move away from each other)
- can form volcanos bc of rising magma
Destructive margin
- occur between a continental + oceanic crust plate
- converging (move towards each other)
- oceanic plate subducts under the continental as its denser
- plates can get stuck underneath each other and when they slip it’s releases lots of pressure creating earthquakes and fold mountains (volcanoes as there’s rising magma)
Collision margin
- occurs when 2 continental plates converge
- both plates of equal density so they stay at same level
- fold mountains are created w no lava bc there’s no rising magma underneath
Conservative margin
- plates move alongside each other
- plates can stick together and friction builds up. When the friction is released, it’s can release as a large earthquake
- no volcanoes as there’s no rising magma
Plate margin
The line where 2 adjacent tectonic plates meet
Focus
The point underground where plates slip and the seismic waves come from
Epicentre
The point directly above the focus on the surface.
Liquefaction
When soft sediment like mud can behave like a liquid when shaken by seismic waves
What is a primary hazard?
a hazard that is caused immediately by event
Secondary hazard of volcanic eruptions/earthquakes
A delayed hazard that was caused by the volcano/ earthquake and was more of the aftermath of the event. eg liquefaction, tsunamis, pyroclastic flow
Stratovolcanoes - found on constructive or destructive margins?
Found in destructive margins such as those of the pacific ring of fire
Stratovolcanoes - do they have acidic or basic lava?
Acidic lava
Stratovolcanoes - explosive or effusive eruptions?
Eruptions are explosive and infrequent as the lava can get stuck in the vents and explode strongly from a pressure buildup
Stratovolcanoes - what is another name for them?
Composite cone, as its formed out of many layers of solidified lava and compressed ash
Stratovolcanoes - what type of base and slope do they have?
They have a narrow base and a steep slope as lava doesn’t travel very far from the base before solidifying
Shield volcano - found on constructive or destructive margins?
Found on constructive margins
Shield volcano - what type of base and slope does it have?
Very wide base and gentle slopes as lava travels very far from vent before solidifying
Shield volcanoes - are eruptions effusive or explosive?
Explosions are effusive and frequent
Shield volcano - does it have acidic or basic lava?
Basic lava
Acidic lava - high or low viscosity?
High viscosity and sticky lava that doesn’t travel far from the vent before solidifying
Acidic lava - high or low temperature?
Relatively low temperature of 800ºC
Basic lava - high or low viscosity?
Low viscosity and runny lava and it travels very far from vent before solidifying
Basic lava - high or low temperature?
High temperatures of 1200ºC
Continental crust - more or less dense?
Less dense crust
Continental crust - what on earth does it make up?
It makes up the earth’s landmasses
Continental crust - how thick is it?
30-50km thick
Continental crust - what is it mostly made of?
It’s mostly made of granite
Oceanic crust - more or less dense?
More dense
Oceanic crust - how thick is it?
Average 7km thick
Oceanic crust - what on earth does it make up?
It forms the earth’s sea floor
Oceanic crust - what’s it mostly made out of?
Basalt
Give 3 reasons why people would live in areas of volcanic hazards
- volcanic ash breaks down to form fertile soil, making it easier and better to farm on
- people may be unaware that they live anywhere that’s hazardous (e.g a dormant volcano for 100s of years)
- people’s family have lived in a hazardous area for generations - a strong tie is developed that makes them reluctant to move elsewhere
Primary hazard of earthquakes and volcanoes example
EQ = shaking + displacement caused by seismic waves
V = pyroclastic flow, volcanic bombs, lava flow
Secondary hazards of earthquakes and volcanoes examples
EQ = landslides, liquefaction and avalanches + tsunamis
V = Lahar, Jokulhaup, tsunamis, climate change
Explain distributivni of earthquakes and volcanoes
- EQ + V correspond to plate margins
- EQ = destructive margins mostly
- V = only constructive and destructive
- Hawaiian hotspot
