Plate Tectonics

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  • Created by: Hologram
  • Created on: 25-01-19 12:04
what are the 4 main sections that make up the structure of the earth?
crust, mantle, outer core, inner core
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how thick is ocean crust?
thin, 5-7 km
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how thick is continental crust?
thick, 10-60 km
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how dense is oceanic crust?
dense, 3.33 (gm/m³)
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how dense is continental crust>
less dense, 2.7 (gm/m³)
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what rock type is oceanic crust?
Basaltic SIMA (Silica and Magnesium)
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what rock type is continental crust?
Granitic SIAl (Silica and Aluminium)
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what is a plate?
a section of earths crust
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how many major tectonic plates are there?
15
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who coined the phrase 'Plate Tectonics' and when?
Tuzo Wilson in 1965
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what is some of the evidence for continental drift?
fit of the continents, fossil evidence, rock type and structural similarity, paleoclimatic evidence, seafloor spreading, paleomagnetism and geomagnetic reversals
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what is an example of the fit of the continents?
the west coast of Africa seems to compliment the shape of the eastcoast of South America
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what is an example of fossil evidence being discovered on different continents?
fossil remains of the freshwater reptile Mesosaurus have been discovered on the continents of both South America and Africa
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what is an example of some paleoclimatic evidence?
glacial till of the same age is found in southern Africa, South America and Australia- areas that would be difficult tio explain the occurence of glaciation
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what is some of the evidence for the theory of plate tectonics?
the topography of the oceans, the age and pattern of ocean basin geology, paleomagnetism and magnetic ********* and the distribution of earthquakes and volcanoes
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how does the topography of the oceans indicate plate tectonics?
sonar techniques developed during WW2 showed that rather being deepest far from land, the ocean had huge, linear mountain ranges, with deep central valleys down the centre
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how does the age and pattern of ocean basin geology indicate plate tectonics?
it was discovered that the amount of material on the ocean floor was much less than expected and samples of the ocean rocks and mid-ocean ridges were made of the very youngest rock`
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how does paleomagnetism and magnetic ********* indicate plate tectonics?
paleomagnetism has allowed researchers to identifywhere crustal rocks were originally formed and where they lie now which revealed a symetrical pattern on the ocean floor rocks across the mid-atlantic ridge
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who came up with the idea of sea floor spreading in the 1960s?
Harry Hess
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what did Harry Hess suggest about sea floor spreading?
that mid-ocean ridges were weak zones in earth's crust where the ocean floor is being pulled apart. New magma rose through these weaker zones and eventually erupt along the ridges, creating new ocean ridges
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what is an example of a volcano rising above the sea level?
in 1963, a volcano rose above the surface of the Atlantic near Iceland to form the island of Surtsey
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is the mechanism by which tectonic plates move still a subject of much debate among scientists?
yes
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what is slab-pull?
where the weight of the descending relatively 'cold' plate drags itself downwards, deep into the mantle and this is what pulls the plate away from the constructive ridges
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what is ridge-push?
where rising plumes of heat energy from the boundary of the mantle and the core stretch plates upwards. At this ocean ridge, new oceanic crust is formed and the plates move under gravity away from the raised ridge
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what are the 3 types of plate boundaries?
constructive/diverging, destructive/converging and conservative/transform
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what is a constructive/diverging plate boundary?
where new crust is generated as the plates pull away from eachother
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what is a destructive/converging plate boundary?
where crust is destroyed as one plate is subducted under another
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what is a conservative/transform plate boundary?
where crust is neither produced nor destroyed as the plates slide horizontally past each other
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what are some examples of constructive/diverging plate boundaries?
Mid-Atlantic Ridge and Rift Valleys (East Africa)
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what is sea-floor spreading?
when convection currents below the earth's surface begin to stretch
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what % of all erupted material occurs at constructive/diverging plate boundaries?
75%
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why do the gaps between the plates in a mid-ocean ridge system not open in a smooth constant movement?
because different parts of the plate edges move at different times due to tension being unevenly distributed along the ridge- this results in transforms faults (this gives the mid-ocean ridge a zig-zag appearance)
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is the crust in a constant of "renewal" at the ocean ridges?
yes
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what is an abyssal plain?
an underwater plain on the deep ocean floor, usually found at depths between 3,000 and 6,000m
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how are abyssal plains formed?
they are the end result of sea floor spreading
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what currents deposit much of the sediment on abyssal plains?
turbidity currents
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where do rift valleys form?
where the earth's crust is spreading or splitting apart- this kind of valley is often narrow, with steep sides and a flat floor
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is it assumed that the process of 'rifting'was responsible for the break-up of Pangaea?
yes
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what are the only 2 rift valleys on Earth within continental crust?
the Baikal Rift Valley and the East African Rift
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what are the 3 types of destructive/converging plate boundaries?
ocean to continent, ocean to ocean, continent to continent
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what is an example of an ocean to continent destructive/converging plate boundary?
along the Peru-Chile trench, the Oceanic Nazca Plate is pushing into and being subducted under the continental part of the South American Plate. In turn the overriding SA plate is being lifted up creating the Andes
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where does an island arc form?
where 2 oceanic plates collide
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what is an example of an island arc formed where 2 oceanic plates collide?
Mariana Islands
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is it true that the farther from the trench, the deeper the earthquakes are?
yes
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what are ocean trenches?
steep depressions in the deepest parts of the ocean
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why are ocean trenches important?
by studying trenches scientists can better understand the physical process of subduction and the causes of these devastating natural disasters, better understand deep sea organisms and may hold the key to biological and biomedical advances
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what do marine communities rely on for nutrients in the trenches with the absence of sunlight?
marine snow- the continual fall of organic material from the abyssal plain and continental shelf and chemosynthesis- the process in which producers in the ocean trench, such as bacteria, convert chemical compounds into organic nutrients
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why doesn't subduction occur at continent to continent collision plate boundaries?
because the continental rocks are relatively light- instead they buckle and fold upwards
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what are some examples of fold mountain ranges?
Andes, Himalayas, Rockies and Alps
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what happens at conservative plate margins?
2 plates slide past each other at different speeds and angles
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where do most transform faults occur?
on the ocean floor
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what is an example of a transform fault on land?
the San Andreas fault in California
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at conservative plate margins what are the 2 ways the relative horizontal movement can be identified as?
sinistral (to the left) and dextral (to the right)
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what often occurs at conservative plate margins?
shallow focus earthquakes
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what are the 2 plates that make up the San Andreas fault?
between the North American and Pacific Plates
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how long and deep is the San Andreas fault?
1,300km long and extends to at least 25km in depth
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in what years did San Francisco suffer significant earthquakes?
1906 and 1989
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where is the Enriquillo-Plantain Garden Fault located?
runs along the southern side of the island of Hispaniola where Haiti and the Dominican Republic are located
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what is an example of a massive earthquake caused by the Enriquillo-Plantain Garden Fault?
in 2010 there was a magnitude 7.0 earthquake which occurred near Port-au-Prince, Haiti
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how many people were killed an injured in the earthquake in Haiti in 2010?
an estimated 220,000 were killed and 300,000+ were injured
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what is orogeny?
a process in which a section of the earth's crust is folded and deformed by lateral compression to form a mountain range.
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how were the Himalayas formed?
formed from the collision of the Indian sub-continent plate into the Eurasian plate
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what are some examples of mountain ranges that are part of the Alps (a long complex fold mountain chain)?
the Atlas, Pyrenes and Apennines
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what are seen as the driving force behind plate tectonic movement and the creation of lines of construction and destruction at plate margins?
sub-lithosphere thermal anomalies or hotspots
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what are fumroles?
an opening in or near a volcano, through which hot sulphurous gases emerge
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what are lahars?
a violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water which flows down from a volcano
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what is a pyroclastic flow?
a dense, destructive mass of very hot ash, lava fragments, and gases ejected explosively from a volcano and typically flowing at great speed
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what are some of the hazards created by volcanic activity?
explosions, ejected materials, landslides, lahars and jokulhlaups
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what is an example of a violent volcanic eruption?
when the Indonesian volcanic island of Krakatoa erupted in 1883, the explosion was heard 4,000km away in Australia, was the loudest sound ever recorded and killed almost 100,000 people
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how are the scale of volcanic eruptions measured?`
using the Volcanic Explosivity Index (VEI)- varies from 0 (non explosive), through 4 (cataclysmic event) to the very rare 8 ( mega-collosal such as the Yellowstone supervolcano event)
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what are some o fthe m,aterials that can be ejected from a volcano?
lava, pyroclastic material and gases
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what are some of the different types of lava?
acid which is viscous and silica rich (eg Andesitic), basic or free-flowing (eg Aa or blocky lava) and Pahoehoe or ropy lava
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what are some of the materials that make up a pyrolclastic flow?
volcanic bombs, stones (lapilli), hot ash and fine dust, pumice, cinders and Nuée ardente
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what is Nuée ardente?
an incandescent cloud of gas, ash, and lava fragments ejected from a volcano, typically as part of a pyroclastic flow
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what are some of the different types of gases that can come out of a volcano?
steam, sulphur dioxide, cabron dioxide, cyanide
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what is an example of volcanic gases having a devastating effect on a community?
on an August night in 1986 at Lake Nyos, a crater lake in Cameroon, West Africa over 1,700 people died of carbon dioxide poisoning in a village 23km away from the crater
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what causes landslides on volcanoes?
volcanoes often bulge as pressure builds up beneath them- this deformation of steep slopes causes landslides
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what is an example of a devastating landslide causes by a volcano?
the eruption of Mt St Helens in 1980 followed the collapse of the north side of the mountain, in the largest landslide ever recorded on film
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what is an example of a lahar occurring?
in 1983, the eruption of Nevado del Ruiz in Columbia resulted in a lahar flowing at 100km/hr through the town of Armero, some 50km from the volcano
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how many people died as a result of the lahar from the eruption of Nevado del Ruiz?
over 20,000 of the 23,000 inhabitants perished
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what is a jokulhlaup?
floods caused by volcanic eruptions beneath ice sheets or glaciers
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where is a country where jokulhlaups frequently occur?
Iceland- due to its 20 volcanoes that lie beneath the ice
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what % of volcanic activity occurs at constructive plate margins?
75%
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what % of the world's active volcanoes are at destructive margins?
80%
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what are some of the features of volcanoes at destructive plate margins?
more violent eruptions and steep cone shaped volcanoes
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what are some of the features of volcanoes at constructive plate margins?
eruptions are generally less violent, gently sloping volcanoes and most are hidden beneath the sea where magma forms bulbous shapes called pillow lava
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what is an example of hot spot volcanoes?
there are many on the island of Hawaii such as Kilauea on Big Island
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what are some of the socio-economic hazards of volcanic activity?
volcanic activity affects both individuals and communities, causing costly damage to infrastructure, agriculture and industry
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what is an example of fatalities being caused by the secondary impacts of an eruption?
after the Skaftá Fires eruption of 1783 in Iceland- there was a famine where a quarter of the population died
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what is an example of an eruption causing mass homelessness and refugee movements?q
the 1991 Mt Pinatubo eruption displaced over 100,000 people, many of whom couldnt return for yeaars if at all
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how many trees did the Mt St Helens eruption flatten and over what area?
flattened millions of tress over a 600km² area
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how much did the ruption of Montserrat (Carribean island) cost the British gov?
£100 million
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what are some of the environmental hazards of an eruption?
the landscape, the ecosystem and the climate
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what is an example of an eruption affecting a landscape?
in 1883, the eruption of Krakatoa replaced a 300m high mountain with a 300m deep submarine crater
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what is an example of an eruption affecting the ecosystem?
one million farm animals died at Piatubo in 1911 and wiped out massive area of vegetation
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what is an example of an eruption affecting the global climate?
in 1815, the cold summer and consequent worldwide crop failures and famine, in which millions died, has been linked to the eruption of Mt Tambara in Indonesia
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what are some of the benefits of volcanic activity?
land creation, fertile soil, mineral deposits, energy and tourism
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what is an example of land creation as a result of volcanic activity?
in 1963 off the coast of Iceland a summit of an underwater volcano formed known as Surtsey
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what are some of the elements that fertile volcanic soil contains?
rich in potassium and phosphorus
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what % of the inhabitants of Sicily live on the slopes of Mt Etna?
20%
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what are some of the crops that are grown on the slopes of Mt Etna?
olives, oranges and wine
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what are some of the mineral depoists that a volcano provides?
deposits of sulphur, pumice and boric acid
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what is an example of a volcano rich in mineral deposits?
at Ljen volcano in Indonesia, local workers climb 200m into the crater to mine sulphur
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what is an example of energy being harnessed from a volcano?
the largest geothermal plant is The Geysers located in the Mayacamas Mountains in California , generating 1,000MW providing 80,000 homes with electricity
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what is an example of a volcano attracting tourism?
in 2001 when Mt Etna erupted during holiday season companies flew and bussed thousands of tourists in to witness this event and the giant causeway is the remnant of lava flow
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what is the economic spin-off created by volcanic tourism?
same as any other type of tourism- creates jobs and income for guides, accommodation, catering, transport and souvenir shops
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where is Mt Pinatubo located?
in the Zambales Mountains in the Phillipines
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how long had Mt Pinatubo been dormant for?
500 years
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what were some of the indicators that preceded the eruption of Mt Pinatubo in 1991?
in 1990 there was a magnitude 7.8 earthquake- thousands of smaller earthquakes occurred after that as well as powerful steam explosions
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when did the first spectacular eruption of Mt Pinatubo occur?
June the 12th 1991
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how high did the ash cloud from Mt Pinatubo reach?
35km in the air
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how thick where some fresh volcanic deposits due to pyroclastic flows?
200m thick
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what happened to Mt Pinatubo after the eruption?
removed so much magma and rock from the volcano that the summit collapsed and formed a caldera 2.5 kms across
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how many people died in the Mt Pinatubo eruption?
847
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how many people were evacuated in the Mt Pinatubo eruption?
75,000
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how many people lost their jobs as a result of the Mt Pinatubo eruption?
650,000
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how much were the damages of the Mt Pinatubo eruption?
$700 million
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what were some of the other economic impacts of the Mt Pinatubo eruption?
1.2 million lost their homes, water was contaminated, road links were destroyed, agriculture of the area was halted, livestock was killed
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what were some of the environmental impacts of the Mt Pinatubo eruption?
heavy rain brought lahars and mudflows that displace homes and destroyed crops, contaminated river systems, 15 million tonnes of sulphur dioxide causing acid rain which kills ecosystems and damages buildings
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what governmental organisation helped predict the volcano?
the US Geological Service helped to predict the disaster by monitoring the volcano and recording changes in land surface
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how did the Philippines prepare for this eruption?
75,000 were evacuated, gov shelter were built, alert systems were put in place and organisations rush as red cross were sent in
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how many lives were estimated to have been saved as a result of the preparation?
5,000
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how much damages were estimated to have been saved as a result of the preparation?
$250 million
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what were some of the short term responses to the eruption?
Philippines gov created the National Disaster Coordinating Council which providing housing for evacuees, medical teams and teachers were provided, advisories were issued for coping with the ash and foreign govs and NGOs provided relief
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what were some of the long term responses to the eruption?
civil engineers tried to isolate lahar deposit sediments that threatened to bury the agricultural field, aim to provide employment alternatives for displaced farmers and workers, improve damaged infrastructure and encourage ecosystems to recover
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what is the result of the eruption 25 years on?
4,000 families still live in resettlement sites, gov has built a 56km wall to trap future lahars, many of the Aetas tribe (tribe that was predominately affected) have found new work and have been able to grow crops again
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what is a volcano?
an opening in Earth's crust that allows for molten rock from beneath the crust to reach the surface. Along with lava, volcanoes also release gases, ash, and rock
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how can volcanoes be categorised?
can be categorised by location (constructive/destructive margin), erupted material (viscous/ non-viscous), shape (shield/composite) and eruption (Hawaiian/Plinian)
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what is often the cause of volcanoes at constructive margins?
the hot asthenosphere/mantle rises to shallow levels, it decompresses and melts to produce non-viscous magmas. This erupts at spreading centres or through lines of weakness in the crust
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what is often the cause of volcanoes at destructive margins?
the magma created by the melting of the subducted plate is critically altered here by the addition of seawater and silica from the abyssal plain- process of hydration melting
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what type of eruption occurs at constructive margins?
eruptions at shield volcanoes are only explosive if water somehow gets into the vent, otherwise they are characterised by low-explosivity fountaining that forms cinder cones and spatter cones at the vent
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what type of eruption occurs at destructive margins?
viscous lavas allow gas pressures to buld up to high levels, leading to explosive eruptions. Fast dangerous eruptions containing a mixture of lava, ash, gas and pyroclastic material
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what type of volcano occurs at constructive margins?
shield volcanoes
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what type of volcano occurs at destructive margins?
composite volcanoes
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what are some examples of volcanoes at constructive margins?
Mauna Loa, Hawaii and Erta Ale, Ethiopia
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what are some examples of volcanoes at destructive margins?
Mt.St Helens, Washington State and Pinatubo, Philippines
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what are some of the socio-economic hazards of lava flows?
both slow and fast moving lava can destroy property and agricultural land (eg 1973 eruption of Heimaey, Iceland), results in loss of homes and economic impacts such as crops etc as they are destroyed- loss of income
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what are some of the environmental hazards of lava flows?
destruction of natural environment- eg vegetation, animal habitats etc
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what are some of the socio-economic hazards of poisonous gases?
Lake Nyos, Cameroon, 1986- CO2 escaped from the volcanic lake, descending down the slopes- 1,700 deaths and 8,000 livestock killed
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what are some of the environmental hazards of poisonous gases?
release of CO2 and sulhpur dioxide can destroy plants/vegetation eg Mammoth Mountain, USA
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what are some of the socio-economic hazards of jokulhlaups?
Grimsvotn, Iceland, 1996- water caused significant damage to infastructure
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what are some of the environmental hazards of jokulhlaups?
Grimsvotn, Iceland, 1996- the jokulhlaup caused subsidence of the glacial lake
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what are some of the socio-economic hazards of pyroclastic flows?
can result in large death tolls and destryos everything in its path, eg Pompeii 79 AD
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what are some of the environmental hazards of pyroclastic flows?
can devastate the natural environment, eg Mt.St Helens flattened several; million trees over an area of 600km
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what are some of the socio-economic hazards of tephra and ash clouds?
direct deaths are rare- however can displace large amounts of people and bury land, eg Mt Pinatubo 1991 displaced over 100,000
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what are some of the environmental hazards of tephra and ash clouds?
devastation of natural environment- vegetation lost as covered by ash and loss of animal habitats, eg Mt Pinatubo 1991 over 1 million farm animals died due to heavy ash falls
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what is tephra?
rock fragments and particles ejected by a volcanic eruption
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what are some of the socio-economic hazards of lahars?
second largest cause of volcanic death, destroys everything in its path and can cause psychological impacts- traumatised people refusing to return to the region even when safe to do so
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what are some of the environmental hazards of lahars?
devastation of the natural environment- bury the land in deposits of mud, metres deep, eg Nevado del Ruiz 1985
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what 3 areas does the management of volcanic activity involve?
prediction, protection and preparation (raising awareness and educating people)
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what is an example of a volcano that is highly predictable?
Mt Etna, Sicily
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of the 700 active volcanoes, how many are continuously surveyed?
70
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what are some of the ways volcanoes can be monitored?
tiltmetres, electronic distance measurement (EDM), hazard mapping, GPS/remote sensing (satellite measurements), gas geochemistry and past eruptive history
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how do tiltmetres help predict volcanoes?
record changes in the slope angle of the flank of the volcano, changes in the angle can signify the rising or falling of magma within the volcano
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how does electronic distance measurement (EDM) help predict volcanoes?
uses a laser light source to measure the distance between two locations, eg checking for changes in the distance across the crater
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how does hazard mapping help predict volcanoes?
showing areas at risk
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how does GPS/remote sensing (satellite measurements) help predict volcanoes?
can measure vertical and horizontal movement sin the volcano. By visiting the same locations every few months volcanologists can determine where and how much the volcano is changing shape
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how does gas geochemistry help predict volcanoes?
the composition of gas or the change in the rate of gas emission provides additional info on what is happening inside the volcano. For example, an increase in the ration of carbon to sulphur can be used to indicate the arrival of a new batch of magma
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how does past eruptive history help predict volcanoes?
analyse volcanic deposits around the volcano to determine their age, type, size and distance from the volcano and direction of past mud flows/lava flows
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what is the Volcanic Explosive Index (VEI)?
similar to the Richter magnitude scale used to measure earthquakes. It has a simple numerical index of increasing magnitude of explosivity,with each interval representing an increase of about a factor of 10 in the volume of erupted tephra
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what rating on the VEI scale have the largest volcanoes in history been given?
8
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how is the VEI measured/ estimated?
volume of products (ash, lava), eruption of cloud height, qualitative observations (using terms ranging from "gentle" to "mega-colossal"
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how many deaths are earthquakes responsible for per year?
10,000
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what depth are shallow earthquakes?
less than 70km from earth's surface
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what depth are intermediate earthquakes?
between 70 and 300km
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what depth are deep earthquakes?
between 300 and 700 km
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is is true that the deeper the earthquakes are the less damaging they are?
yes
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what are the two common causes of earthquakes?
release of stress between rocks at plate boundary and movement of magma within the crust beneath active volcanoes
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what does the abbreviation "L" mean for seimic waves?
surface wave
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what are some of the features of primary waves?
type of body wave, first to arrive (fastest wave type), travels through solids liquids and gasses
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what are some of the features of secondary waves?
type of body wave, second to arrive (slower wave) and travels through solids but not liquids
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what are some of the features of surface waves?
travels along the surface of the earth, last to arrive (slowest), ground motion is a rolling action like waves on a pond
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what happens during primary waves?
ground stretches and squeezes in the direction of wave travel
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what happens during secondary waves?
ground motion is at right angles to the direction of the wave travel
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what instruments can be used to monitor earthquakes?
seismometers, creepmeters, magnetometers, strainmeters, tiltmeters
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what are seismometers?
instruments which measure motions of the ground, including those of seismic waves- data is recorded on a seismograph
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what is a creepmeter?
records the displacement between 2 points opposite sides of faults- but can suffer from seasonal changes, heavy rainfall and nearby quakes
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what is a magnetometer?
measure changes in local magnetic fields resulting from a combination of mean crustal stress and fault slip
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what are strainmeters?
measure crustal strain and are highly sensitive instruments- there are some of these instruments on the San ANdreas fault
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what are tiltmetres?
highly sensitive instruments that can be used to measure ground tilt near faults and volcanoes caused by fault slip and volcanic uplift
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what does the richter scale measure?
the magnitude of an earthquake- it is objective
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what does the mercalli scale measure?
intensity of the earthquake- it is subjective
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what are some examples of modifications that can be made to buildings to help them be better adapted to earthquakes?
rolling weights on the roof, latticework steel foundations into the bedrock, latticework steel cage to stabilise building, rubber shock absorbers between foundations and building ground above
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why are building designs based on triangles more earthquake resistant than rectangular forms?
most waves produce a lateral side-to-side motion
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what is 'pancaking'
shaking which causes one floor to collapse allowing the structure above to crumple- this happened to high rise buildings in Kobe
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what are some of the secondary impacts of seismic shaking?
landslides, fires and floods
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what is liquefaction?
a phenomenon in which strength and stiffness of a soil is reduced by earthquake shaking
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in what soils does liquefaction occur?
occurs in saturated soils, that is, soils in which the space between individual particles is completely filled with water
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what happens to the soil during liquefaction?
the shaking can cause the water pressure to increase to the point where the soil partilces can readily move with respect to eachother- the strength of the soil decreases and the ability to support foundations for buidings is reduced
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what is an example of an earthquake where liquefaction occurred?
overturned apartment buildings in Niigata in 1964- Japan
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what is an example of liquefaction triggering landslides and collapsing dams?
the Lower San Fernando Dam suffered an underwater slide during the San Fransisco earthquake in 1971
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what can be done to prevent liquefaction?
dynamic interactive simulation between the structure and the soil liquefaction ground as well as info required to select the appropriate earthquake resistance in buildings and liquefaction countermeasures
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what are the 3 Ps for seismic event management?
prediction, prevention and protection
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how can earthquakes be predicted?
through 'characteristic earthquake analysis', 'seismic gap theory' and analysis of seismic activity to help create maps that predict where seismic events may occur
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what are some of the ways which earthquakes can be predicted?
eliminate large eqs by deliberately causing smaller ones by deliberately setting off explosions at fault lines to remove the pressure that may be building up and lubricating fault lines to help prevent the jerking and jolting movement?
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why are the problems with these preventions?
far too many small earthquakes would be required to offset one large eq and the USGS believes that lubricating fault lines could actually trigger an eq
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what are some of the methods of protection for an eq?
eq proof buildings, education (eg drills and 'grab bags' for emergency evacuation), fire prevention, land-use planning (eg low land value uses such as parks can be built in high risk areas, insurance and training
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when did the Tohoku earthquake and tsunami occur?
11th of March, 2011
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what magnitude was the Tohoku earthquake?
9.0
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where was the epicentre of the Tohoku earthquake located?
130 kms east of Sandai on the east coast of Honshu
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what caused the Tohoku earthquake?
resulted from thrust faulting on or near the subduction zone plate boundary between the Pacific and Eurasian plates
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how high did the tsunami waves reach that were triggered by the Tohoku earthquake?
40.5m
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how many people were killed by the Tohoku earthquake and tsunami?
almost 16,000
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how many people were injured by the Tohoku earthquake and tsunami?
over 5,000
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how many buildings were destroyed or damaged by the Tohoku earthquake and tsunami?
330,000
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where did most of the damage and casualties occur?
Iwate, Fukushima and Miyagi
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what was the total economic loss to Japan as a result of the Tohoku earthquake and tsunami?
$309 billion
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how many houses lost access to water supplies as a result of the Tohoku earthquake and tsunami?
1.5 million
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where did liquefaction occur as a result of the Tohoku earthquake and tsunami?
Chiba, Tokyo and Odabia
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what were some of the responses to the Tohoku earthquake and tsunami?
the gov mobilised the self-defense forces, the Japanese Red Cross reported $1b in donations, area around Fukushima nuclear power plant was evacuated and over 300,000 were displaced
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what tidal defense did Japan had
sea walls- covered 40% of the coastline which some stand at 12m high-however the tsunami simply washed over them collapsing some of them in the process
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what has the Japanese gov done to help combat seismic activity?
Disaster Reduction and Human Renovation Institution (DRI) and has also built a research centre in downtown Kobe dedicated to eq research
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what other response did the Japanese gov take after the Tohoku earthquake and tsunami?
a massive sea wall to improve tsunami defenses- $6.8b plan that will link 440 sections of wall together forming a 400km long wall at 12m high
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what is an example of a precursor of an eq?
water well at Kobe- in 1995 the level of radon gas in the water was monitored and on the 7thg of Jan radon surged to high levels and on the 10th of Jan it dropped to very low levels- the eq struck one week later
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what is the dilation theory?
states that as rocks along fault lines become stressed they expand (dilate) and numerous microscopic cracks open up- if recognisable patterns in these things can be observed then it may be possible to use them to predict future eqs
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what are some of the consequences as a result of dilation that could possibly be observed?
change in speed of seismic waves travelling back through the rock , changes in its magnetic and electrical properties and an increase in the release of gases such as radon
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what is an example of a place where the dilation theory was put to the test?
Parkfield, California following the Loma Prieta eq in 1989 which lies on the San Andreas fault
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was the experiment at Parkfield successful?
no- the scientists incorrectly predicted the next earthquake which they assumed would occur roughly 20 yrs after the eq in 1989- only a medium sized eq has occured since then in 2004 which produced no precursors at all
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what is a seismic gap?
a section of fault that hasn't moved seismically over an unusually long time period
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what is an example of an eq that helps prove this theory?
the Loma Prieta eq in 1989- although there had been seismic movement beforehand, by the mid 1980s three sections hadn't moved in 20 years- San Francisco, Parkfield and Loma Prieta. When the fault moved in 1989 it filled the Loma Prieta gap
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what are some of the social impacts of seismic activity?
death and injury, human fear/anxiety/PTSD, building damage, phone road and rail lines disrupted, underground services fractured eg pipes, fires may start, homelessness, closure of businesses and huge cost of rebuilding
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what are some of the environmental impacts of an eq?
landslides moving or overwhelming buildings, liquefaction and tsunamis
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what are some of the things you can do to prepare for an eq?
make your building safer (eg bolt bookcases to the wall), keep a supply of canned food and up to date first aid kit
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what are some of the things you can to keep safe when eq shaking begins?
drop down, take cover under a desk, identify a safe place in each room where it is unlikely something will fall on you, if you're outdoors find a clearing away from buildings, trees etc and tune in to a local radio
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Card 5

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