earthquakes and volcanoes Flashcards
Define epicentre
The point on the Earth’s crust that is directly above the centre of the earthquake.
Define focus
Where the pressure is released underground and where the energy radiates out from
Describe the features of a stratovolcano
Found at destructive tectonic plate
boundaries
Extremely violent
Thick lava
steep sides
Describe the features of a shield volcano
Gently sloping sides
Less violent (slow lava flow)
Found at constructive tectonic plates or hotspots
Thin lava
No ash produced
Made of layers of lava
List the effects of an earthquake
Death
Loss of home
Fire
Water pipes burst
Water contamination
Spread of diseases
Tsunami might follow
Reconstruction costs
Buildings damaged
Hard accessibility to essentials
Why do people live in areas where earthquakes can occur?
Occupationally immobile
Geographically immobile –> cannot afford to move
Unaware of the consequences
Family ties
Believes it isn’t going to occur
List the effects of a volcanic eruption
Deaths
Land destruction: homes, transport,
jobs
Fire
Unemployment
Rebuilding costs
Poor sanitation
Gas suffocation from eruptions
Pyroclastic flow
Loss of habitats
Hard accessibility
Describe the hazards of a volcanic eruption
Famine + disease (Destruction of housing, not clean water supply, lack of food etc.)
Lava flows (Destruction of buildings, roads, transport)
Pyroclastic flow: Hot, solid material which travels down rapidly on slopes –> Cannot escape in time
Ash falls –> Damages property by burying buildings + hazards to aircrafts
Acid rain (Sulfur dioxide + hydrogen sulfate → damages buildings, animals, plants by rainfall)
Tsunami –> Collapse of volcanoes into the sea
List the opportunities near volcanoes
Tourist site –> job opportunities
Fertile soil –> lava and ashes form rich, thick soil layer
Minerals and mining –> Sulfur around the active volcano → benefits economy for trade
Creates landmass –> Produces new islands, enlarging existing landmass
Geothermal power from underneath rocks
How can you prepare for an earthquake?
Build earthquake-proof buildings + roads
Practice drills
Educate children about evacuation
Train emergency services
Set up warning systems/signs
Create an evacuation plan
Emergency food and water supply
monitoring systems/example, e.g. lasers
tsunami warnings
warnings sent to cell phones
evacuation
hazard mapping/areas not built on
strong foundations, (allow deeper)
strengthening, e.g. diagonal bracing
ground isolation systems
How can you prepare for a volcanic eruption?
Setup warning system
Create an evacuation plan
Train emergency services
Educate students about evacuation
Post-eruption plans
Emergency food and water supply
Describe the features of collision plate boundaries
Where continental meets continental
Plates being forced together at great pressure
Rocks crumble together and form massive mountain chains
No volcanoes
Violent earthquakes
Fold mountains
Example: Himalayas
Describe the features of constructive plate boundaries
Where any 2 types of plate boundaries move apart from each other (go the other way) e.g Eurasian and North American
There can never be any gaps on Earth
When tectonic plates pull apart magma, the mantle rises up and solidifies to fill the empty space
this process in repeated many times over a long period. Eventually forming a shield volcano.
Gentle volcanoes
Gentle earthquakes
No fold mountains
Describe the features of destructive plate boundaries
where oceanic meets continental e.g Nazca and South American
convection currents cause the plates at a destructive plate boundary to collide
oceanic is denser
oceanic is subducted
friction from each crust pushing together can cause an earthquake and causes the oceanic plate to heat up
the oceanic plate melts to form magma
magma makes its way up through the cracks in continental crust and forms a volcano on the surface
violent earthquakes
violent volcanoes
fold mountains
Shield volcano characteristics
Gently sloping sides,
lava pours out with little violence,
cone with wide base and gentle slopes,
far reaching lava, less viscous lava,
regular and frequent eruptions,
low silica content in lava
Describe the features of conservative plate boundaries
When plates move alongside each other in opposite directions or in the same direction but at different speeds
convection currents cause plates to either move
Made up of rock that is brittle and jagged so it is difficult for the plates to slide past each other
the plates don’t always slide smoothly alongside each other and friction can cause them to become stuck together
this pressure builds up until one “jerks” past the other causing an earthquake
Sudden movement and release of pressure causes earthquakes
No volcanoes are formed from conservative plate boundaries
Example: San Andreas Fault
Composite volcano characteristics
Violent eruptions,
tall cone with narrow base and steep sides,
made of alternate layers of lava and ash,
viscous (sticky) lava,
irregular eruptions with long dormant periods,
acidic (high silica content) lava
Earthquakes
Vibrations in the earths crust that shake the ground surface
Epicentre
the point on the Earth’s surface directly above the focus of an earthquake
Focus
The point inside the crust where the pressure is released
Why are earthquakes of the same magnitude likely to cause more damage in LEDCs than MEDCs?
- poor quality building so they easily collapse
- building regulations are not enforced
- buildings are not earthquake proof
- poor medical services and so people cannot be properly treated for their injuries
- poor education about earthquake precautions
- in LEDCs they have to wait longer for rescue teams
Hotspots
An area of the earths crust that is associated with volcanic activity.
Approx 125 hotspots have been active over the past 10 million years.
Most are located away from plate boundaries.
Why do people live in areas where earthquakes occur?
- they can’t afford to move and have nowhere else to go
- they have lived there all their lives
- there is work and education available
- relatives and friends are in the area
- confidence in precautions and buildings
- people don’t think it’ll happen
How can you predict a volcanic eruption?
Temp increases prior to an eruption
change in shape recorded by a tiltmeter
earthquakes occur prior to an eruption
- can be recorded by a seismometer
volcanic gases are emitted prior to an eruption
look at history of eruptions
