Flashcards
Plate tectonics - Seismicity
Cards in this deck (37)
- 1What 2 characteristics are there of earthquakes?1) VOLCANIC ACTIVITY
- Small tremors caused by rising magma under a volcano
- The resultant energy from an explosive volcanic eruption
2) TECTONIC ACTIVITY
- When the tectonic plates are moving in different directions, there are faults. The friction of rock movement causes friction so stresses build up in the rocks. When the stored energy is released shockwaves radiate out from the source. - 2What is the focus of an earthquake?The focus is the point where the energy is released, deep in the earth’s crust.
The most damaging earthquakes are shallow focus quakes (0 – 70km). - 3What is the epicentre of an earthquake?The epicentre is the point on the earth’s surface immediately above the focus. This is the point at which there is most seismic energy.
- 4What are seismic waves?Shock waves released by the rupture of rock strata at the focus of an Earthquake
- 5What are he characteristics of Primary (P) waves?1) travel fastest
2) Compressional
3) Vibrate in the direction in which they travelling
4) Travel through the interior of the earth and are recorded on a seismograph
4) Can move through solids and liquids - 6What are the characteristics of Secondary (s) waves?1) Half the speed of P waves
2) Shear rock by vibrating at right angles to the direction of travel
3) Cannot move through liquids but do much more damage than P-waves
4) Travel through the interior of the earth and are recorded on a seismograph
- 7What are the characteristics of Surface (L) waves?1) Travel slowest
2) Near to the ground surface
3) Shake the ground at right angles to the direction of wave movement
- 8What is the mercalli scale?1) Considers intensity of event and impact
2) Level I would be equivalent to 2 on richter scale
3) level XII represents total destruction and 8.5 on richter scale. - 9What are the problems with the mercalli scale?1) Not in use in uninhabited areas
2) Statements such as heavy traffic only work if someone feels there is heavy traffic
3) impacts very in different areas so may be multiple values for same earthquake - 10What is the Richter scale?1) A logarithmic scale
2) measures at 7 are 10x greater than at 6 and release 30x more energy
3) Largest measured on sclae was great Chilean earthquake of 1960, measured 9.5.
4) Largest UK earthquake was 4.8. - 11What are the problems with Richter scale?1) Doesn't take into account amount of damage; an earthquake which may cause collosal damage in one place would cause little damage in an uninhabited area.
- 12What is a tsunami?A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, usually an ocean. They occur frequently in Japan; approximately 195 events have been recorded. Owing to the immense volumes of water and high energy involved, tsunamis can devastate coastal regions. More effect if the focus is closer to land
- 13How are tsunamis formed?1)Tsunami’s are usually triggered by earthquakes
2) The crust shifting is the primary effect and a knock-on effect of this (secondary) is the displacement of water above the moving crust (start of a tsunami)
3) A normal wind-driven wave may have a length of 100m from crest to crest
4) A tsunami wave aver. 200km in length
5) The heights also greatly differ: 2m for a normal wave vs. 1m for a tsunami at sea
6) Tsunamis move at speeds of around 800kph, rapidly approaching the coast almost unnoticed
7) As they land they slow, reduce in length and gain in height - 14What is drawback?.If the first part of a tsunami to reach land is a trough rather than a wave crest, the water along the shoreline recedes dramatically, exposing normally exposed areas.A drawback occurs because the tectonic plate one one side of the fault line sinks suddenly during the earthquake, causing overlaying water to propagate outwards
- 15CASE STUDY EARTHQUAKE/TSUNAMI: MEDC, Japan (date,location, affected areas, richter scale)1)March 11th 2011
2) Earthquake measured 9.0 on the Richter scale
3) Occurred 100km east of Sendai on Honshu, Japan
4) In just 30 minutes a wall of water up to 40m high hit the coast of NW Japan
5) It was followed in places by up to 9 additional ‘waves’ of up to 10m in height
6) 3,000 km of coastline were affected by the waves, which tore through coastal defences and inundated the coastal plain - 16What were the causes of the earthquake?1) The earthquake that triggered the tsunami occurred at the destructive plate margin where the Pacific plate is being subducted beneath the NA plate
2) Scientists believe that a segment of rock, some 200km in length slipped suddenly resulting in an upwards ‘flick’ of the earth’s crust by between 5-10cm.
3) It was this sudden uplift that triggered the tsunami - 17Effects: Killed, buildings destroyed,, farmland, communications1. 20 000 died; power of the surge of water over topped tsunami defences and flooded 'safe' areas
2. 125 000 builidings destroyed
3. Some 500km squared of coastal plains were inundated, destroying farmland, settlementsand communications - 18Effects: ExplosionsExplosions occurred at the Fukushima Nuclear power plant as seawater over-topped theflood defences – there were considerable concerns about nuclear contamination and thepossibility of a meltdown as the cooling systems failed to operate
- 19Effects: Electricity, water, gas?1) Ruptured gas pipes led to fires that raged for several days
2) Electricity was cut off in almost six million homes and over one million people were leftwithout running wate - 20Effects: Stock marketsStock markets around the world fell over concerns about Japan’s rising debts of billions of US$ worth of damage
5% drop in Tokyo stock market - 21Responses: Over countriesOver 100,000 Japanese soldiers were deployed in search and rescue. They distributed blankets, water and food to the people affected by the disaster. Additionally specialist search and rescue teams were sent in form over seas
- 22Responses: FukushimaAn exclusion zone was set up around the Fukushima nuclear plant and people wereevacuated from the area
200 000 evacuated
20km evacuation - 23Response: Long termIn the longer-term, a huge re-building and reconstruction programme is planned involvinghouses, infrastructure and communications systems (roads, railways etc.) Port facilities willneed to be re-built and may well be extended in height beyond the standard 12m that iscurrently the accepted level
- 24LEDC EARTHQUAKE/TSUNAMI: Indian Ocean 2004!
- 25What are the causes of this tsunami?1) 26th December 2004
2) Earthquake caused by subduction of Indo-Australian plate under european plate
3) 240km off coast of Indonesia
4) 20m uplift of sea floor along faultline which was over 1 000km in length
5) Billions of tonnes of water displaced - 26What were the economic effects of the earthquake$10 billion in 24 hours
1) Ports ruined.
2) Fishing industry devastated. 100 00 boats destroyed. estimated 60% of Sri Lanka’s fishing fleet destroyed (5 million people).
3) Reconstruction cost billions of dollars.
4) Loss of earnings from tourism - foreign visitors to Phuket dropped 80% in 2005.
5) Communications damaged, eg roads, bridges and rail networks. - 27What were the social impacts of the tsunami?1) 230 000 deaths.
2) 1.7 million homeless.
3) 430 000 homes destroyed
3) 5-6 million needing emergency aid, eg food and water.
4) Threat of disease from mixing of fresh water, sewage and salt water.
5) 1,500 villages destroyed in northern Sumatra.
6) 2200 miles of road destroyed - 28What were the environmental impatts of he tsunami?1) Crops destroyed.
2) Farm land ruined by salt water.
3) 8 million litres of oil escaped from oil plants in Indonesia.
4) Mangrove forests along the coast were destroyed.
5) Coral reefs and coastal wetlands damaged - 29What were the immediate responses?1) Search and rescue.
2) Emergency food and water.
3) Medical care.
4) Temporary shelter.
5) Re-establishing infrastructure and communications. - 30What were the secondary responses of the tsunami/earthquake?1) Re-building and improving infrastructure and housing.
2) Providing jobs and supporting small businesses.
3) Giving advice and technical assistance. - 31What were the short term responses?1) Many areas local communities were cut off and had to help themselves.
2) Authorities ordered quick burial or burning of the dead to avoid the spread of disease.
3) Food aid was provided to millions of people, eg from the World Food Programme.
4) $7 billion (just under £4.5billion) of aid was promised by foreign governments – but there were complaints that not all money pledged was given.
5) British public gave £330 million through charities, eg the average Actionaid donation was £84 – their best ever response
5) 5 million relocated to refugee camps - 32What were the long term responses?1)Reconstruction is still taking place.
2) Local scale: some small-scale sustainable development projects have been set up by charities to aid recovery and help local people help themselves to rebuild and set up small business
3) A tsunami early warning system has been installed at a cost of $20 million
4) The Indonesian government decided to move refugees straight into new homes but it took longer than expected due to a lack of supplies and the destruction of transport routes - 33How can you predict an earthquake?1) Impossible to exactly predict when or where but understanding plate tectonics gives us a greater understanding
2) Monitoring groundwater levels, unusual animal behaviour
3) Fault lines such as San Andreas can be measured
4) Seisometers measure micro earthquakes - 34How can you predict earthquakes?1) You cannot fully predict earthquakes
2) Earthquake systems can detect waves only after they have occurred
3) Japanese earthquake early warning system set up in 2007 (warns by TV/radio) warnings may only come a few moments before earthquake
4) data of past earthquakes. - 35How can you build against earthquakes?1) Buildings built to withstand earthquakes (strong materials such as reinforced concrete or special foundations)
2) Construction laws in earthquake prone areas - USA or Japan have new buildings which are more able to withstand earthquakes - 36How can you predict tsunamis?1) Rely of earthquake detection systems
2) Tsunami warning centres around the globe. - 37How can you build against tsunamis?1) Buildings designed with raised open foundations made of strong materials
2) Tsunami walls may be built around settlements
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- A-Level Geography (A2) Flashcards on Plate tectonics - Seismicity, created by Ella Foster on 31/03/2017.
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