earthquakes and volcanoes Flashcards
What are earthquakes
Earthquakes are a sudden violent shaking of the ground, as a result of movements within the Earth’s crust or volcanic action
What are the causes of earthquakes
Earthquakes are caused by all types of plate boundaries
Sometimes, because of friction, plates try to move and become stuck. Pressure builds up because the plates are still trying to move. When the pressure is released, it sends out huge amounts of energy causing the Earth’s surface to shake violently.
What is the focus
The point inside the Earth’s crust where the earthquake originates from is known as the focus.
What are seismic waves
The earthquake’s energy is released in seismic waves and they spread out from the focus.
what is the epicentre
The seismic waves are most powerful at the epicentre.
The epicentre is the point on the Earth’s surface directly above the focus.
What are the factors affecting level of damage earthquake
- Distance from the epicentre - the effects of an earthquake are more severe at its centre.
- The higher on the Richter scale, the more severe the earthquake is.
- Level of development (MEDC or LEDC) - MEDCs are more likely to have the resources and technology for monitoring, prediction and response.
- Population density (rural or urban area). The more densely populated an area, the more likely there are to be deaths and casualties.
- Communication - accessibility for rescue teams.
- Time of day influences whether people are in their homes, at work or travelling. A severe earthquake at rush hour in a densely populated urban area could have devastating effects.
- The time of year and climate will influence survival rates and the rate at which disease can spread.
how to measure earthquakes
The power of an earthquake is measured using a seismometer. A seismometer detects the vibrations caused by an earthquake. It plots these vibrations on a seismograph.
We use the Richter Scale to categorize the intensity of different magnitudes
What are the 4 types of plate boundaries
Constructive
Destructive
Conservative
Collision
What are constructive plate boundaries + characteristics
At constructive boundaries two plates are moving apart. Molten magma rises to the surface, cools and solidifies to form new oceanic crust.
The magma is hot and runny (non viscous) so volcanic eruptions are gentle and non explosive
Destructive plate boundaries + characteristics
Destructive boundaries are when dense (heavy) oceanic crust are subducted beneath less dense continental crust.
Intense heat and pressure in the subduction zone creates molten magma which rises to the surface to form explosive volcanoes.
Powerful earthquakes also occur.
Conservative plate boundaries + characteristics
At conservative boundaries two plates are grinding slowly past each other horizontally.
There is no volcanic activity but powerful earthquakes occur.
Collision plate boundaries + characteristics
Collision margins are where two continental plates collide. The continental crust is too thick to allow subduction.
Instead sedimentary rock is forced upwards to form huge mountain ranges like the Himalayas.
There is no volcanic activity.
What are hotspots
Hot spots cause volcanic activity away from plate margins. As the plate moves over the stationary hot spot, a series of volcanoes are formed. The most famous example is the Hawaiian Islands.
How are fold mountains formed
by Collison plate boundaries
What is the crust
a layer of sand and rock varying from 5-50 km thick
What is the mantle
A rock layer about 2850 km thick that reaches about half the distance to the centre of the earth. Parts of this layer become hot enough to liquify and become slow moving molten rock or magma
Outer core
a mass of molten iron about 2200 km thick that surrounds the solid inner core
Inner core
a mass of iron with a temperature of 3870. Normally iron would melt at this temperature, but its immense pressure keeps it solid. Its 2400 km in diamaeter
Process of convection cycle
- The heat rises off the core and travels through the mantle
- The heat moves the magma upwards until it hits the bottom of the crust
- The heated magma spreads sideways below the crust, dragging the plates along
- The heated magma cools and eventually settles down back to the core
- The core reheats the magma, continuing the cycle
What is oceanic crust
Oceanic crust: younger, heavier, can sink and is constantly being destroyed and replaced
What is continental crust
Continental crust: older, lighter, cannot sink and is permanent
What are the effects of earthquakes
Large number of deaths Fires breaking out Water pipes burst Water contamination, diseases Corpses: human & animal Accessibility difficult Building damaged/destroyed Tsunami can follow Reconstruction costs
What are prediction methods for earthquake
- Measure earth tremors, pressure, and release of gas
- Use maps and facts to find pattern in time/location
- Unusual animal behaviour
What are preparation methods for earthquakes
-Build earthquake-proof buildings and roads
-Train emergency services
-Set up warning system
Create evacuation plan
Emergency food supply
Practice drills
Earthquake proof buildings features
Automated weights on roof to reduce movement
Fire-resistant building material
No bricks or reinforced concrete block
Rubber shock-absorbers between foundations
Foundation sunk deep into bedrock avoiding clay
Roads to provide access by ambulances & fire engines
Open areas where people can assemble if evacuated
Automatic shutters come down over the windows
Interlocking steel frames which can sway during earth movements
What are volcanos
A vent in the earth’s surface where magma, gas or ash escapes onto the earth’s surface or into the atmosphere.
causes of volcanoes
At constructive margin: plates move away from each other; magma rises to fill the gap;
At destructive margin: oceanic crust melts from friction and heat from mantle; newly formed magma is lighter so it rises to surface
advantages of volcanoes
Tourist attraction: income and employment
Creates fertile soil: good agricultural land to grow crops
Geothermal heating: Renewable resource, Heating (hot water), Geyser & mud baths
Disadvantages of volcanoes
Destruction of land, property, jobs, homes, transport Rebuilding costs Unemployment Fires breakout Diseases from poor sanitation Gas from eruption suffocates Pyroclastic flow
prediction for volcano
Animal behaviour changes
Emits gas & steam
When was the monserrat explosion
1995 18 july
25 june 1997
Short term response monserrat
Evacuation
Abandonment of the capital city
The British government gave money for compensation and redevelopment
Long term response monserrat
An exclusion zone was set up in the volcanic region
A volcanic observatory was built to monitor the volcano
short term impacts monserrat
Evacuation of almost 5,000 residents
Delta was created by the flow of lava into the sea
The eruption left the southern two-thirds of the islands completely inhabitable
The following settlements were destroyed : Bethel, Bramble, Dyers, Fairfield, Farm, Farrell’s, Galway’s Estate, Harris, Hermitage, Long Ground, Morris’s, Plymouth, Saint Patrick’s, Tobuscus Mt, Soufrière, Streatham, W. H. Bramble Airport.
montserrat long term impacts
The eruption left the southern two-thirds of the islands completely inhabitable.
Pyroclastic flows still pour down the slopes of the volcano.
The eruptions continued after the volcano became active.
The disaster resulted in the collapse of tourism and also the local rice processing industries.
Unemployment shot up from a manageable 7% to over 50%.
Agricultural activities became nearly impossible and living conditions were further worsened by respiratory problems caused by the spewing ash
benefits montserrat
Volcano tourism increased
A new delta was formed
More businesses were developed in the north
The airport and several roads had to be rebuilt, resulting in new facilities
When was the tohoku japanese earthquake
2011 11 march
Short term effects tohoku
Death and injury: roughly 16,000 people died, 6,000 injured and 2,500 people went missing
330,000 buildings, 2000 roads, 56 bridges and 26 railways were destroyed or damaged
300 hospitals were damaged and 111 were totally destroyed
Blackouts for almost 4.4 millions households in japan
Long term effects tohoku
Destroyed 46,027 buildings
Cost an estimated $360 billion in damage
Crippled Japan’s nuclear industry
Led to huge trade deficits (A trade deficit occurs when a country’s imports exceed its exports during a given period.) as japan had to import oil after electricity went down after nuclear plants took damage
short term response tohoku
Rescue services moved very quickly to the affected areas to clear roads, in order to move the silts and to count the number of deaths
Army helped to provide temporary shelter for the homeless
The Japanese Red Cross received over $1 billion in donations and they gave out over 30,000 emergency relief kits and 14,000 sleeping kits.
The people tried to go back to their normals lives within a few weeks
Long term response tohoku
Used 23 trillion yen to rebuild the houses
Replace tsunami barriers with 18m high instead of 12m
Took 1 ½ years for the production of manufacturing companies to begin again (eg) toyota, honda)
example of collision plate noundary
indo austrailia plate
example of constructive plate boundary
north american plate
Example of conservative plate boundary
pacific plate
Example of destrutive plate
eurasian plate
example of shield volcano
mauna loa hawaii
Example of composite volcano
mount fuji japan
