hazardous earth Flashcards

Question

how do the age of sea floor rocks evidence sea floor spreading?

Answer 1

the prediction was that oceanic rocks would get older the further one was from the mid-ocean ridge. the cores also showed that nowhere in the oceans was rock older than 200 million years. this confirmed that the ocean crust was constantly recycled over this period

Answer 2

divergent (constructive), convergent (destructive) and conservative

Answer 3

large scale faults in the crust at right angles to a mid ocean ridge, which range from a few tens of km to several hundred. earthquakes occur along their lengths as they slip

Answer 4

broad and smooth mountain chains; no central rift valleys **eg East Pacific Rise (Pacific and Nazca plates)**

Answer 5

poorly defined central rift valleys; relatively smooth mountain chains **eg Galapagos Ridge (just south of the Nazca and Cocos plate boundary)**

Answer 6

steep slopes to mountain chains; clearly defined central rift valleys

Answer 7

the eruption of magma along divergent boundaries occurs mostly underwater. Magma erupting directly on to the sea bed is cooled rapidly, forming rounded mounds called pillow lavas

Answer 8

as magma rises towards the surface, the pressure reduces and it liquefies. The overlying rocks are forced upwards as the lithosphere is placed under stress and eventually fractures. This produces the underwater rift valleys.. In the North Atlantic, the extrusion of magma has been so great it has created the world's largest volcanic island -- Iceland.

Answer 9

at mid ocean ridges, sea water seeps into rifts and is superheated. As it rises towards the surface it causes chemical changes in the basaltic rocks. Superheated jets of water sometimes re emerge on the ocean floor containing metal sulphides. These features are commonly known as black smokers and support unique and highly specialised organisms and ecosystems

Answer 10

rift zones are not confined to the ocean floor; they also occur on land in part explain how continents can break up. the continental crust must thin considerably for rifting to occur one of the best examples is the rift stretching from the Red Sea northwards to Turkey. Here, the crust has been uplifted and stretched, causing faulting and forming a sunken valley known as a GRABEN. as the rift widened, magma erupted at the surface. eventually, the rift valley sank below sea level, forming the present day Red Sea. If the crust continues to thin here, magma will well up to form a new spreading boundary between Africa and the Arabian Peninsula. Further north in Israel, the rift dips below sea level, forming the Dead Sea.

Answer 11

when oceanic and continental plates converge, the denser oceanic plate is forced under the continental plate.

Answer 12

layers of sediment and sedimentary rock develops on oceanic plates adjacent to continents. As an oceanic plate converges on a continental plate, these sediments and rocks crumple, fold and are uplifted along the leading edge of the continental plate. In addition, the continental crust is buckled and uplifted, and significant amounts of molten material are injected into it.

Answer 13

boundary between a subducting ocean plate and the over-riding continental plate at a destructive boundary

Answer 14

between 30 and 70 degrees faulting and fracturing occur in the Benioff zone, where the descending plate is at an angle close to 45 degrees. This process releases considerable amounts of energy in the form of earthquakes

Answer 15

when two oceanic plates meet, the slightly older and therefore denser one will subduct under the other, creating a trench. **as the plate descends, dehydration takes place causing partial melting of the mantle wedge in the plate above. this magma rises to the surface and forms chains of volcanic islands known as island arcs.**

Answer 16

little, if any, subduction takes place. This is because the two plates have similar densities. In Europe, the collision of the African and Eurasian plates over the last 40 million years has created the Alps

Answer 17

where plates slide past each other volcanic activity absent bc no subduction takes place frictional resistance to movement along the plate boundaries often causes the build up of pressure. from time to time these pressures cause rocks to fracture, releasing enormous amounts of energy as the pressure is released, causing earthquakes

Answer 18

in California, where the NA and Pacific plates, although moving in the same direction, are doing so at different rates

Answer 19

convergent plate boundaries

Answer 20

divergent plate boundaries

Answer 21

rhyolite (more acid) andesite (less acid)

Answer 22

acid (high % silica), high viscosity, lower temp at eruption

Answer 23

basic (low % silica), low viscosity, higher temperature at eruption

Answer 24

violent bursting of gas bubbles when magma reaches surface highly explosive vent and top of cone often shattered

Answer 25

gas bubbles expand freely limited explosive force

Answer 26

gas, dust, ash, lava bombs, tephra

Answer 27

gas, lava flows

Answer 28

tend to have long periods with no activity

Answer 29

tend to be more frequent an eruption can continue for many months

Answer 30

steep sided strato-volcanoes; caldera

Answer 31

gently sloping sides, shield volcanoes lava plateaux when eruption from multiple fissures

Answer 32

characterised by persistent fissure eruption. Large quantities of basaltic lava build up horizontal plains

Answer 33

involve more noticeable central activity than the Icelandic type. runny, basaltic lava travels down the sides of the volcano in lava flows gases escape easily occasional pyroclastic activity occurs

Answer 34

characterised by frequent gas explosions which blast fragments of runny lava into the air to form cones they are very large explosive eruptions with large quantities of pyroclastics thrown out

Answer 35

violent gas explosions blast out plugs of sticky or cooled lava. fragments build up into cones of ash and pumice vulcanian eruptions occur when there is very viscous lava which solidifies rapidly often the eruption clears a blocked vent and spews large quantities of volcanic ash into the atmosphere

Answer 36

characterised by very powerful blasts of gas creating ash clouds high into the sky they are more violent than vulcanian eruptions lava flows also occur

Answer 37

gas rushes up through sticky lava and blasts ash and fragments into the sky in a huge explosion the violent eruptions create large clouds of gas and pyroclastics along with the lava these clouds can rush down the slopes part of the volcano may be blasted away during the eruption

Answer 38

this diversity is related to where the eruption occurs, the type of lava, the variety of materials (such as ash, pumice and gases) produced, and how the eruption takes place for example, differences in the chemistry of the magma influences the type of eruption and the shape of the volcano once magma is ejected at the surface, its behaviour is affected by its viscosity, which in turn is determined by its chemical composition and temperature, and the changes that take place to magma within the magma chamber

Answer 39

sometimes known as composite cone volcanoes are made up of layers of ash and acid lava have concave symmetrical profiles most contain complex internal networks of lava flows which form minor igneous features such as sills and dykes because **acid magma does not flow easily, the vents are often filled with a mass of solidified magma, which prevents magma from rising freely from depth. as a result, enormous pressures can build up inside a volcano until it eventually erupts explosively, sometimes literally blowing its top off**

Answer 40

a minor, approximately horizontal, intrusion of magma into surrounding older rocks

Answer 41

a vertical or near vertical minor intrusion of magma through surrounding older rocks

Answer 42

volcanic craters, usually more than 2km in diameter they develop when an explosive eruption destroys much of the cone and the underlying magma chamber is largely emptied **without the support of the underground magma, the sides of the volcano collapse to form a caldera** the 1883 eruption of Krakatoa in Indonesia left a caldera 7km wide

Answer 43

convergent plate boundaries and explosive eruptions often give rise to chains of stratovolcanoes Indonesia, for example, has 130 active stratovolcanoes along its archipelago, while in the Andes, 66 stratovolcanoes have erupted in recorded history

Answer 44

that volcanoes are unpredictable and resist easy classification for example, Icelandic volcanoes include stratovolcanoes, shield volcanoes and fissures

Answer 45

when basic magma erupts from multiple fissures, vast areas can be covered by free-flowing lava. these events are known as flood basalts examples include **the Deccan Plateau in central India, which covers more than 500,000km2**, known as an LIP (large igneous province), while the Columbia Plateau in NW USA covers 130,000km2 however, millions of years of denundation have created more varied relief. no large scale flood basalt events have taken place in the past 50 million years. When they do occur they have a devestating impact on the atmosphere and hydrosphere, and consequentially the biosphere

Answer 46

effusive eruptions are usually found at divergent plate boundaries. Because these boundaries coincide with mid-ocean ridges, most effusive eruptions occur unseen on the ocean floor Iceland is an exception. It owes its formation to effusive volcanic activity and is one of the most active volcanic regions in the world eruptions of basic lava result in volcanoes with gently sloping sides if successive flows accumulate for long enough, huge volcanoes, extending horizontally for tens of kilometres, **such as Skjaldbreidur on Iceland,** can develop

Answer 47

a fixed area of intense volcanic activity where magma from a rising mantle plume reaches the Earth's surface

Answer 48

as the pacific plate has moved northwest over the Hawaiian hot spot (at an average rate of 10cm/year), vast amounts of basalt have accumulated on the ocean floor to produce the Hawaiian islands

Answer 49

over millions of years, as the pacific plate move northwest and over the hotspot, the volcanoes lose their source of magma and become extinct thus, on the older islands in the Hawaiian chain, such as Kauai, volcanism is no longer active. there, weathering and erosion have broken down the volcanic rocks into deep and fertile soils. further along the chain to the NW, the volcanic islands have sunk below the surface of the Pacific to form underwater mountains or seamounts

Answer 50

a volcano that erupts more than 1000km3 of material in a single eruption event is known as a super volcano. the evidence of past and perhaps future super volcanic activity is the existence of giant calderas. eg The Yellowstone supervolcano in Wyoming has a caldera measuring 75km in diameter the most recent supervolcanic eruption occured 27,000 years ago at Taupo, New Zealand. The impact of these very high magnitude events is deduced from the extent and depth of ash layers and their impact on plant, insect and animal species

Answer 51

magnitude (the amount of material erupted) intensity (the speed at which material is erupted)

Answer 52

the Volcanic Explosivity Index (VEI) it combines magnitude and intensity into a single number on a scale from 0, the least explosive, to 8, the most explosive

Answer 53

the volume of erupted material the height ejected material reaches the duration in hours various qualitative descriptions

Answer 54

The VEI is not that useful for effusive eruptions such as those on Hawaii. However, it is valuable in suggesting the relative impacts volcanoes might have at different geographical scales

Answer 55

these are massive effusive outpourings of basalt that commonly erupt intermittently over very long periods of time and typically cover areas between 2000-2500km across. one of the largest of them, the Siberian Traps, has a total volume of 3 million km3 which would be enough to bury the whole of western Europe under a 1km thick sheet of basalt

Answer 56

is that they are formed by mantle plumes of very hot but solid material that rises from the junction between the mantle and the liquid outer core; the same process that creates convection currents in the mantle the material making up the plume is mafic but changes chemically by the time that it reaches the surface depending on whether the last leg of the plume's route to the surface is through the oceanic crust or continental

Answer 57

LIP events are devastating. Millions of cubic km of magma ponds up below the lithosphere before periodically breaking through the lithosphere and crust, erupting over several million years the amount of material produced might create global cooling initially, as other eruptions have historic time, but given that CO2 is the most significant gas emitted by most effusive eruptions, the long term impact is global warming and ocean acidification LIP events have been identified as possible causes for at least four major extinctions, including the Permian extinction. Each of these were brought about by significant peaks in atmospheric CO2

Answer 58

some Earth scientists propose that supervolcanoes and hot spots are the final remnants of past LIP events about 15 million years ago, a LIP created the Columbia River flood-basalts in what is now the NW of USA. That corresponds to where the Yellowstone caldera would have been located at the time. In its current hot spot position, volcanic activity began about 2 million years ago when a giant caldera formed. Two further huge eruptions took place 1.3 million years and 640,000 years ago. In addition to these, dozens of smaller eruptions occured bc the evidence of earlier eruptions may have been either buried or destroyed by later ones, it is not known exactly how often the volcano has erupted, nor the volume of material extruded. during the largest eruptions, ash was spread over much of the western half of NA, while gases and tiny particulates were carried around the globe in the upper atmosphere

Answer 59

**the impacts are dependent on type of lava**. Basic (basaltic) lava is free-flowing and can run for considerable distances on hawaii in july 2015, a lava flow extended from 20km before stopping and in August the same year a flow was reported to have covered about 800m in a day acidic lavas such as rhyolite are thick and pasty so do not flow easily. everything in the path of lava will be either burned, bulldozed or buried. Although they destroy infrastructure, property and crops, lava flows rarely cause injuries or fatalities

Answer 60

a combination of very hot gases, ash and rock fragments travelling at high speed. they follow the contours of the ground and destroy everything in their path the inhalation of such hot and poisonous gas and ash causes almost instant death Pompeii was overwhelmed by a pyroclastic flow from Vesuvius in AD 79

Answer 61

this describes any material ejected from a volcano into the air ranges in size from very fine ash to large volcanic bombs also includes lighter debris such as pumice potentially very hazardous, burying farmland in layers of ash and destroying crops eruption columns can carry material into the stratosphere largely bc the temp of ejected material is always much hotter than the surrounding air, so it rises very fast, in addition to the propulsion of the explosion itself buildings can collapse due to the weight of accumulated ash and people with respiratory diseases may have difficulty breathing

Answer 62

eruptions emit a wide range of toxic gases, including CO, CO2 and SO2. these can pose a deadly threat to humans when SO2 combines with atmospheric water, acid rain is produced. this can damage crops and pollute surface water and soils

Answer 63

these are a type of mud flow with the consistency of wet concrete snow and ice on a volcano summit melt during an eruption and flow rapidly down the cone rock fragments large and small, as well as ash and soil, are mixed together **can travel at speeds up to about 50km/h. everything in their path is either destroyed or buried under thick layers of debris** in places such as southeast asia, ash-covered slopes of volcanoes continue to generate lahar hazards after periods of heavy rain

Answer 64

volcanic eruptions beneath an ice field or glacier cause rapid melting in iceland, several active volcanoes lie under the Vatnajokull ice field. during an eruption, vast quantities of water accumulate until they find an exit from under the ice. the resulting torrent of water is known locally as a JOKULHLAUP

Answer 65

the violent eruption of some island volcanoes can cause massive displacement of ocean water and tsunami waves capable of travelling at speeds of up to 600km/h approaching the shore, tsunami waves increase rapidly in height and when they break transfer vast amounts of energy and water along the shore and inland the tsunamis created by the eruption of Krakatoa in 1883 are believed to have drowned 36,000 people

Answer 66

past eruptions of super-volcanoes such as Toba, Indonesia led to reductions in global temperatures as ash blocked sunlight from reaching the Earth's surface, and has been linked with a dramatic fall in the global human population at the time

Answer 67

lake nyos is one of a number of deep lakes that occupy volcanic craters in Cameroon in West Africa it is 2km wide and 200m deep in August 1986, 1700 people and all animal life in the area around the volcano were asphyxiated. the cause was a leak of CO2 from a volcanic crater lake. the gas had built up at the bottom of the lake after being emitted from the underlying magma chamber when the CO2 escaped it flowed down the volcano slopes as a 50m thick ground hugging layer travelling at about 70km/h it is not known for certain what caused the CO2 to escape the lake. possible explanations are a deep movement of magma, an earthquake, a change in water temp in the lake, or strong winds stirring up the lake waters, much like shaking a fizzy drink

Answer 68

earthquakes represent the release of stress that has built up within the Earth's crust caused by tension, compression or the shearing of rocks

Answer 69

point at the surface directly above an earthquake focus

Answer 70

Pompeii was overwhelmed by a pyroclastic flow from Mount Vesuvius in AD 79

Answer 71

the eruption of Iceland's Eyjafjallajokull volcano in April 2010 led to the cancellation of 100,000 flights

Answer 72

in 1984, following the eruption of Nevado del Ruiz, the Colombian town of Armero was overwhelmed by lahars, resulting in the deaths of 23,000 people

Answer 73

mid ocean ridges: tensional forces associated with spreading processes and subsequent faulting and rifting ocean trenches and island arcs: compressive forces associated with the subduction of one plate below another collision zones: compressive forces associated with the grinding together of plates carrying continental crust conservative plate margins: shearing forces associated with the intermittent movement of one plate past another

Answer 74

P WAVES-- fast travelling, low frequency compressional waves. They vibrate in the direction in which they travel S WAVES-- half the speed of P waves, high frequency waves. they vibrate at right angles to the direction in which they travel L WAVES-- slowest of the three types, low frequency waves. some L waves have a rolling movement that moves the surface vertically, while others move the ground at right angles to the direction of the movement

Answer 75

L waves travel through the outer crust only S waves cannot pass through liquids (and so cannot travel through the outer core) P waves travel through the Earth's interior (through both solids and liquids)

Answer 76

surface down to about 70km occur in cold brittle rocks, resulting from the fracturing of rock due to stress within the crust very common, with many releasing only low levels of energy, although other high energy shallow quakes are capable of causing severe impacts

Answer 77

70-700km. are poorly understood with increasing depth, pressure and temperatures increase to very high levels. minerals change type and volume, which may contribute to a release of energy. it is likely that dehydration of water in subducting plates plays a significant role in these events but scientists continue to evolve their ideas about these less frequent but often powerful quakes

Answer 78

uses the amplitude of seismic waves to determine earthquake magnitude. logarithmic scale has no upper limit, though the largest earthquakes record a magnitude of around 9 (eg Tohoku, Japan 2011) is not used to express damage. an earthquake's damage is determined partly by magnitude but also by other factors such as population density and levels of preparedness

Answer 79

measures earthquake intensity and its impact relates ground movement to impacts that can be felt and seen by anyone in the affected location is a qualitative assessment based upon observation and description

Answer 80

measures the energy released by the earthquake more accurately than the Richter scale the amount of energy released is related to the geological properties such as the rock rigidity, area of the fault surface and amount of movement on the fault also logarithmic provides the most accurate measurement of large earthquakes as it uses the amount of physical movement caused by an earthquake, which is a direct function of energy not used for small earthquakes

Answer 81

on geological timescales and across areas covering many thousands of squarek km, earthquakes are associated with the formation of entire mountain chains such as the Himalaya-Karakoram Range in Asia. The northward drift of India into Eurasia and the subsequent continental collision led to a complex pattern of folding and faulting of rocks

Answer 82

to the north of the Himalaya-Karakoram Range lies the Tibetan Plateau. averaging 4500m above sea level it covers an area of 2.5 million km2 major fault systems are evident in the rocks and these indicate considerable movement the entire region is tectonically active, as the 2008 and 2013 earthquakes in Sichuan province and 2015 event in Nepal demonstrated

Answer 83

a tilt block forming an extensive upland area, with a short, steep (scarp) slope and a long, gentle (dip) slope

Answer 84

a cliff or escarpment formed directly by rocks being displaced either side of a fault

Answer 85

rift valleys on the continents are altered by weathering and erosion. over time fault scarps are worn away, blending into the landscape. they can even disappear under accumulated sediments

Answer 86

this is the vertical and horizontal movement of the ground. the severity of ground shaking depends on: - earthquake magnitude - distance from the epicentre - local geology locations that are close to the epicentre of a high magnitude quake and where the surface layers are relatively unconsolidated and have a high water content will experience extreme ground shaking. these conditions existed in parts of Mexico City and the Japanese port of Kobe hit by devastating earthquakes in 1985 and 1995 respectively

Answer 87

in general, most buildings can withstand vertical movements better than horizontal ones: it is the swaying of structures that is so dangerous to their stability. ground movements that cause displacement of rocks along fault lines can rip apart pipelines and sewers, sever rigid structures such as railway tracks and roads, and cause buildings to collapse the displacement of the surface can also disrupt natural drainage, diverting streams and rivers and affecting the movement of groundwater in aquifers. this can have serious implications for public water supplies and irrigation for agriculture

Answer 88

when an earthquake strikes an area with surface materials of fine-grained sands, alluvium and landfill with a high water content, the vibrations can cause these materials to behave like liquids. as a result, these materials lose their strength and structures tilt and sink as their foundations give way

Answer 89

liquefaction was a major issue during the Kobe earthquake as much of the port had been built on reclaimed land in Osaka Bay. Just under 200 berths in the port were destroyed, affecting not just the Japanese economy but trade throughout the world

Answer 90

steep slopes in mountainous regions like the Himalaya-Karakoram range are notoriously unstable and vulnerable to landslides. their vulnerability is increased by deforestation and heavy monsoon rains, so that even small tremors can trigger landslides the nepalese earthquake of 2015 triggered large numbers of landslides and avalanches caused by ground shaking

Answer 91

block transport routes in mountainous regions where accessibility is already difficult movement of soil and rock on slopes can also block rivers. these natural dams create temporary lakes, which can threaten areas downstream with catastrophic floods. this was the case in several locations in Kashmir in 2005 and Sichuan in 2008 should an earthquake creates a landslide on slopes above a reservoir, the displacement of waters and the waves generated could weaken and overtop the dam eg an earthquake did this in italy in 1963. it led to the collapse of a hillside above the vaiont reservoir, generating a 100m wave which swept over the dam and down the valley of the Piave river, drowning nearly 3000 people

Answer 92

underwater earthquakes can cause the sea bed to rise vertically this displaces the water above, producing powerful waves at the surface which spread out at high velocity from the epicentre. because of their low height and very long wave length, tsunami waves can pass underneath a ship out at sea unnoticed. However, wave height increases greatly as they approach the shore and enter shallow water before the wave breaks, water in front of the wave is pulled back out to sea, a process known as drawdown, finally, the tsunami wave rushes in as a wall of water that can exceed 25m in height

Answer 93

estimated to have delivered about 1000 tonnes of water per metre of shoreline

Answer 94

they displace water and create tsunami waves when a large volume of rock is shaken and slides downslope, water is dragged in behind it from all sides and collides in the centre. this can generate a tsunami wave which radiates outwards while the resulting wave may not have enough power to cross oceans, the local effects can be devastating. for example in 1998, 2200 villagers living in coastal communities in Papua New Guinea were killed by a local tsunami generated from an underwater landslide triggered by an earthquake, because such events are local, warning times are short, making them particularly hazardous

Answer 95

movements along plate boundaries lying just offshore of the japanese mainland create an ever-present risk of tsunamis the pacific coastal zone is especially vulnerable, being densely populated and containing three huge conurbations: Tokyo, Osaka and Nagoya

Answer 96

11 March 2011

Answer 97

occurred along the boundary between the Pacific and North American plates its epicentre was 70km offshore of northeast Honshu Island was an undersea megathrust earthquake

Answer 98

Honshu island moved 2.4m east the Earth shifted on its axis by 10-25cm a 400km stretch of coastline dropped vertically by 0.6m sea bed rose by about 7m and moved westwards by 40-50m

Answer 99

claimed nearly 16,000 lives and injured another 6000 people mass mortality and destruction of crematoria, morgues and the power infrastructure created problems of how to dispose of the dead bodies. traditional funeral traditions were waived-- the authorities felt they had no choice but to bury bodies in mass graves as quickly as possible to reduce the chances of diseases being spread Save the Children reported that 100,000 children were affected. The problem was made worse as most children were at school when the earthquake struck **the destruction of infrastructure (eg housing, schools and health centres) was on such a scale that reconstruction was still taking place ten years after the disaster.** Some communities have even been relocated from their original settlement site

Answer 100

cost of the earthquake, including reconstruction, has been estimated at anything between US$200 billion and nearly five times that amount

Answer 101

Japan's National Police Agency issued an official figure of 45,700 buildings destroyed, with a further 143,300 damaged.

Answer 102

15 ports were directly affected, with four destroyed in the NE of Japan, including Sendia. 10% of Japan's fishing ports were damaged, although most had reopened a year after the earthquake

Answer 103

4.4 million households and thousands of businesses lost electricity. The major cause of this disruption was the immediate shutdown of 11 nuclear reactors at the Fukushima Daiichi nuclear power plant, all six of its reactors were so severely damaged by the tsunami that the plant was decommissioned. the plant's cooling systems were disabled by sea water flooding, which led to a meltdown of reactor cores and the release of radioactivity a 30km evacuation zone was established around the plant, and soils in the surrounding countryside were contaminated by radiation. **even today radioactivity continues to seep into the Pacific Ocean, affecting the fishing industry and incurring further costs** Japan experienced several weeks of power cuts (lasting 3-4 hours at a time), which added to the economic cost of the earthquake. Two oil refineries were set on fire during the earthquake, one fire taking ten days to put out

Answer 104

transport infrastructure was badly hit many road bridges were damaged or destroyed and in the north east train services were badly disrupted twenty-three train stations were swept away, while others suffered severe damage, such as collapsed roofs

Answer 105

some 25 million tonnes of debris was created by the earthquake, requiring a costly clean up operation over large areas, farmland flooded by sea water has been contaminated by salt and made uncultivable

Answer 106

japan's stock markets fell as the implications for businesses such as Sony, Toyota and Panasonic were realised. their production was hit by the shortage of electricity. overseas operations were also affected, as supplies of parts exported from Japan were interrupted

Answer 107

a large popular movement against nuclear power developed after the Tohoku earthquake. Concerns over safety standards and regulation of the nuclear industry became a political issue it emerged that warnings about the inadequacy of the defences against tsunami hazards had been made several years before the disaster political fallout from the Fukushima nuclear accident spread around the world. for example, in Western Europe, the anti-nuclear lobby in Germany used the incident to support their arguments against nuclear power

Answer 108

12 January 2010 7.0MW A slip along a 40km section of the Enriquillo fault Epicentre 25km southwest of Port-au-Prince, the capital city Focus = 12km Shaking lasted 12-14 seconds with significant aftershocks within 20 minutes of 6.0 MW and 5.7 NW, and then another of 5.9 MW on 20 January Total of 51 aftershocks >4.5 MW in the year after the initial 12 January event Haiti had no seismic network to record the earthquake

Answer 109

official figures place deaths at 316,000 but other estimates based on survey data suggest a much lower figure between 46,000 and 84,000 over 300,000 houses and 30,000 commercial buildings were either damaged or destroyed, displacing as many as 1.5 million people, many of whom were forced to live in camps many of the destroyed and damaged houses were in the poorest areas of the city, built on steep slopes prone to landslides. By 2020, ten years after the earthquake, over 30,000 people still lived in those camps

Answer 110

as a secondary effect of the earthquake, a cholera epidemic broke out in October 2010; the first case was detected close to the UN base for Nepalese troops bought in to help with the reconstruction effort. Since the first case over 800,000 cases of cholera have been recorded **the official number of deaths was, in 2020, put at just under 10,000. Once again, this figure is disputed; one epidemiologist puts it at 8 times that number**

Answer 111

since the earthquake, the economy ha barely recovered aid money has not, by and large, been directed at an economic recovery, with schemes such as the establishment of tourism and a more diverse economy less reliant on US companies that have not delivered very much the Haitian economy has hardly grown since the earthquake. Its largest income sources are remittances: money sent to the country by expatriate Haitians working abroad, providing 25% of its GDP, followed by foreign aid, which provides 20% of its annual budget. A weak and corrupt government still struggles to collect tax income

Answer 112

risk = (frequency or magnitude of hazard x Level of vulnerability) / capacity of population to cope and adapt

Answer 113

frequency of earthquakes and volcanic activity magnitude of earthquakes and volcanic activity types of hazards generated by earthquakes and volcanoes in a particular location number of people living in an earthquake-prone and/or an eruption-prone area

Answer 114

vulnerability is concerned with the ability of a person or community to withstand exposure to, and risks from, a hazard such as an earthquake or volcanic eruption. people are most vulnerable when relatively small physical changes have major socio-economic implications

Answer 115

resilience is an indication of the rate of recovery from a hazardous event that has put an individual and/or community under stress it is about how well an individual and society are able to function at an acceptable level when a destabilising force has affected them

Answer 116

not possible for the vast majority of volcanic eruptions. however, the following have been tried with some success: - lava diversion channels - spraying lava to cool it so it solidifies - slowing lava flows by dropping concrete blocks Nothing can be done to modify an earthquake event.

Answer 117

EDUCATION: recognise the signs of possible eruption; what to do when an eruption occurs; drills to practise what to do when a tectonic event strikes COMMUNITY PREPAREDNESS: eg building of tsunami shelters and walls; strengthening of public buildings PREDICTION AND WARNING: increasing use of technology to monitor particularly active locations eg individual volcanoes HAZARD-RESISTANT BUILDING DESIGN: eg cross-bracing of buildings to support them during an earthquake; steep sloping rooves to prevent ash building up HAZARD MAPPING, eg predicted lahar routes; ground likely to liquify in an earthquake LAND USE ZONING to avoid building in locations identified by hazard mapping

Answer 118

emergency aid, eg bottled water, medical supplies, tents, food packs disaster-response teams and equipment, eg helicopters and heavy lifting machinery search and rescue strategies insurance for buildings and businesses resources for rebuilding public services, eg schools and hospitals, and help for individuals to rebuild homes and businesses

Answer 119

an active volcano is one that has erupted since the last glacial period or within the past 10,000 years

Answer 120

one that has not erupted during the past 10,000 years but is expected to erupt some time in the future

Answer 121

one that is not expected to erupt again

Answer 122

Mount Ontake is a **classic strato-volcano situated 200km west of Tokyo** on Japan's largest island, Honshu **had been dormant for many centuries** until a **sequence of eruptions between October 1979 and April 1980.** Further eruptions followed in 1991 and 2007 **the area was popular with climbers and trekkers and was a noted tourist destination** , with various facilities including a lodge close to the summit. **It was also a place of spiritual pilgrimage for many Japanese people**

Answer 123

On 27 September 2014, just before midday, Mount Ontake erupted violently and without warning. at the time the volcano was not under any alerts or warnings, although some increase in earthquake activity has been observed. the eruption killed 63 people and large areas surrounding the volcano were affected by ash fall, pyroclastic flows, volcanic bombs and lahars most casualties were climbers and hikers on the slopes of the volcano. More than 200 survivors made it down the mountain and search and rescue teams were deployed to recover those seriously injured

Answer 124

even in Japan, with one of the most sophisticated monitoring and warning systems anywhere in the world, the country can be taken by surprise by the unpredictability of tectonic hazards

Answer 125

complex, with widespread subduction along the entire 3000km length of the Indonesian archipelago much of indonesia is an island arc formed by subduction of the Indo-Australian plate beneath the Eurasian plate. a feature of volcanism in Indonesia is the large number of volcanoes that are highly explosive. This was exemplified by the cataclysmic eruption of Krakatau in 1883, which also generated a devastating tsunami. In the north of Sumatra, Lake Toba fills the caldera caused by the devastating eruption of the super-volcano 70,000 years ago

Answer 126

merapi is a stratovolcano which reaches nearly 3000m in altitude. it is highly active, with eruption events in 1994, 1997, 2001 and 2006. On each occasion, a dome developed in the crater, which eventually collapsed, producing pyroclastic flows. The force of these eruptions was 3-4 VEI.

Answer 127

the VEI 4 eruption between **26 October and 12 November 2010** affected people living around the volcano pyroclastic flows extended 4km to the north, 11.5km to the west, 7km to the east and 15km to the south lava bombs were thrown 4km from the summit in all directions. the eruption happened at the start of the rainy season, triggering lahars fed by ash from the eruption and from earlier eruptions

Answer 128

ash falls forced the closure of Yogyakarta airport for over a fortnight

Answer 129

emissions of sulphur dioxide caused acid to fall over a large portion of the region

Answer 130

367 people were killed 277 injured 410,000 in the vicinity became refugees

Answer 131

large numbers of livestock killed ash fall and pyroclastic flows amounting to 130 million m3 of material destroyed crops and infrastructure such as buildings, power lines and bridges

Answer 132

the slopes of volcanoes often attract settlement weathered lava produces fertile soils especially in wet tropical regions. intensive farming therefore supports very high population densities. Japan's agricultural sector uses just 13 per cent of the country's land area but does so very intensively. In part this is possible due to the high fertility of volcanic soils in both Indonesia and Japan, the steep-sided slopes of the strato-volcanoes have been terraced to allow farming to be practised. HOWEVER, colder climates like icelands mean there are no agricultural benefits of living close to volcanoes. The basalt lava flows remain largely unweathered and is a hostile environment for plants

Answer 133

iceland has developed geothermal energy from 'hot rocks' to help it become 100% renewable in its production of electricity japan also has had geothermal power stations since the 1960s but these were small scale interest and research into geothermal energy were also given a major boost in the aftermath of the 2011 earthquake in Japan One issue Japan faces in exploiting its geothermal energy resources is that nearly 80% of the hot rock locations are in national parks or protected hot spring locations

Answer 134

indonesia also has a vast geothermal energy potential and is beginning to exploit this currently, only about 3% of Indonesia's total electricity comes from geothermal but there are plans to increase this Sarulla power plant has the potential to be the world's largest such plant

Answer 135

multi storey buildings can sway, especially towards their tops. a stepped profile gives considerable stability against lateral forces

Answer 136

how rigorously building codes and laws are applied in most locations, many buildings were built before the rules became law retro-fitting measures are very expensive and may not always be possible even in ACs

Answer 137

established in 1920 its key division is the Volcano Observation Section, which over the years has constructed permanent observatories on several active volcanoes. first seismograph was set up on Mount Merapi in 1924, but as with monitoring elsewhere, the capability of the technology at the time was limited Indonesia was a Dutch colony until the end of the Second World War. Its emergence into independence was accompanied by political tension and violence among competing groups. Managing volcanoes was therefore given a low priority

Answer 138

today more than 60 volcanoes are monitored. Sophisticated equipment measures gas emissions, inflation as magma rises and earthquake activity in some, but not all of Indonesia's volcanoes

Answer 139

in association with university-based researchers, both Indonesian and foreign, lahar sensors and closed-circuit television have been installed to monitor locations and greatest risk

Answer 140

the CVGHM works closely with local governments, advising them on mitigation strategies such as community preparedness additionally, on Mount Merapi for example, permanent settlement is forbidden on the highest slopes around the crater. **Villagers on the southern slopes (at greatest risk) have been encouraged to relocate to safe zones, in some cases receiving financial assistance and a small plot of lands as incentives to move**

Answer 141

an enduring problem is that people have a strong bond with their village site and their family fields. They often return, rebuild and accept the risks

Answer 142

indonesia is a lower-middle-income country, so the resources it can deploy once an eruption is underway are limited. many of the farming communities affected also have limited resources. That said, Indonesia has some well-trained and well-equipped emergency services, including the military, experienced in search and rescue. Temporary shelters in safe zones are available in case of evacuation and sometimes these are upgraded into permanent residential areas **the authorities have also cleared river channels of volcanic material and other debris in order to reduce the risk of flooding and to contain lahars. Some of this material has a commercial value (eg road building) and people living along the river valleys have used it for rebuilding houses and communities facilities.**

Answer 143

italy has had some local scale success with slowing and diverting lava flows from Etna Earth barriers, large concrete blocks dropped into the lava flow and channels dug to divert flowing lava away from settlement have been used

Answer 144

monitoring plays a significant role in mitigating eruption hazards, providing accurate information to the **Volcano Risk Service** (CFCRV), which is the basis of decision-making such as evacuation orders. The CFCRV includes: - long term analysis of the eruption patterns of individual volcanoes - international comparison with similar eruptions elsewhere - constant monitoring, eg seismometers, tilt meters, analysis of gas emissions, aerial and satellite survey eg infrared to detect heat. **daily and weekly bulletins are issued** - a well established alert-level sequence understood by emergency services, all levels of government and local communities - close of airports and air space when threatened by ash in the atmosphere - **much work carried out to identify the types of housing most at risk and to offer affordable solutions, eg adding a pitched roof to an existing flat roof, which will then shed ash fall**

Answer 145

with frequent eruptions from etna, italy is well practiced in dealing with volcanic hazards. the italian government has **the resources to compensate individuals and businesses and restore infrastructure** **casualties have been minimal thanks to timely evacuation based on accurate data and well trained public services such as the fire service, the police and the military**

Answer 146

prior to the 2010 earthquake there was no monitoring system in Haiti. following the earthquake, the USGS has helped with earthquake awareness and monitoring in the country, with continued support from the US Agency for International Development (USAID). a total of 15 seismic stations are now operating in haiti. unfortunately, the monitoring facilities are not earthquake resistant and there is not enough money to staff a 24 hour team

Answer 147

progress has been made with hazard maps developed where none existed before, showing areas especially at risk, such as areas with softer sediments liable to liquefaction however, there is no national disaster risk management plan; there is no 'Japanese' style education programme so that children know what to do in the next earthquake

Answer 148

the inability of the state to enforce earthquake-resistant building design there is no government approved building code and given that the country has had four presidents and seven prime ministers since 2010, stability and long-term planning are not evident for example, the Bureau of Mines and Energy, which oversees earthquake surveillance among many other responsibilities, has an annual budget of just $US 600,000, which is 0.04% per cent of the national budget

Answer 149

with no effective government of its own, the role of NGOs in Haiti has been critical but has been controversial from the start At the International Donors Conference 'Towards a New Future for Haiti' (March 2010), donors pledged over $US5.3 billion to be spent over two years. However, as international donations flooded in (45% of US households donated to Haitian charities), the dream of a constructive did not, for the most part, happen critics argue that from the very start, NGOs followed their own agendas and set their own priorities, largely excluding the Haitian government and its people. in the first rush of aid after the earthquake, just 1% of all donor funds available for emergency assistance was offered to the Haitian government almost two-thirds of the money raised for the charitable NGOs (in the billions) remains in the bank accounts of the aid money managers that were there before the earthquake there have been a series of scandals surrounding the work of NGOs in Haiti, including the behaviour of some of their senior officials

Answer 150

the Japan Meteorological Agency (JMA) lies at the heart of Japan's mitigation strategies for natural disasters, including earthquakes and tsunamis and extreme weather events such as typhoons it is responsible for providing information and warnings of impending earthquakes and tsunamis. **detailed disaster planning involves a wide range of organisations, eg governments, medical services, fire, military etc**

Answer 151

steel frames and braces capable of moving without collapsing rubber shock absorbers in foundations very deep foundations in solid rock flexible joints in underground utility pipes, eg gas and water

Answer 152

fire proofing older wooden buildings, which are common in historic districts of Japanese cities

Answer 153

land use zoning that provides for open spaces where people can assemble after an earthquake

Answer 154

controlling building in locations susceptible to excessive ground shaking or liquefaction tsunami warning systems off the coast refuge sites on permanent stand-by equipped with tents, bottled water, blankets community preparedness-- ongoing education and training for all ages

Answer 155

being one of the most advanced countries in the world, Japan has vast resources to manage losses caused by earthquakes. Well-rehearsed recovery and reconstruction plans, at national, regional and local levels, can be actioned immediately following an earthquake the aim is to rebuild physically, economically and socially as quickly as possible

Answer 156

Stage 1: normality Stage 2: hazardous event, rapid detioration follows Stage 3: search, rescue and care Stage 4: Relief and rehabilitation period, may include outside help. Quality of life etc gradually improves Stage 5: Nature of recovery related to the need to reduce vulnerability and the need to restore normality as soon as possible. Could end in either improvement or return to normality

hazardous earth Flashcards

(183 cards)