natural hazards - tectonics

Question 1

what is a natural hazard

Answer 1

natural event that has a huge social impact

Question 2

different types of natural hazards

Answer 2

volcanic eruptions
earthquakes
storms
tsunami
landslides
floods

Question 3

what is hazard risk

Answer 3

probability of being affected by natural event

Question 4

what factors affect hazard risk? (urbanisation, climate change, farming, poverty)

Answer 4

urbanisation - some of world’s most densely populate areas are most at risk of natural risks
climate change - leads to more intense storms and hurricanes
farming - farmland at risk of flooding
poverty - may have to live in areas of risk - unstable slopes prone to landslides

Question 5

development of plate tectonic theory

Answer 5

continents used to be joined together (pangaea), continents parted due to continental drift
sonar used to find underwater mountain ranges similar to above water

Question 6

oceanic plate

Answer 6

relatively recently formed, thin and dense - basalt (black lava flow)

Question 7

continental plate

Answer 7

older, thicker, less dense - granite

Question 8

constructive plate margin

Answer 8

two plates move apart from each other, magma forces to surface, causes rock to fracture and crack, leads to earthquakes
magma escapes as lava, very hot, flows long distances before cooling, flat and broad volcanoes (shield), eruptions fiery, non-explosive
(mid-atlantic ridge through atlantic ocean)

Question 9

destructive plate margin

Answer 9

1. two continental plates move towards one another, collide, crumpling, uplifting crust, leads to formation of fold mountain ranges, powerful earthquakes, no volcanoes, no magma (himalayas from indo-australian and eurasian)
2. dense oceanic plate subducts under less dense continental plate, heated, melts to form magma, friction triggers earthquakes, magma viscous to composite volcanoes conical shaped, violent eruptions - ash clouds, pyroclastic flows (nazca plate beneath south american plate)

Question 10

conservative plate margin

Answer 10

plates slide alongside each other, stresses built up by friction suddenly released creates earthquakes, no volcanic activity cuz no magma

Question 11

convection currents

Answer 11

currents of heat, rising magma at constructive plate margins when plates move apart

Question 12

gravitational sliding

Answer 12

ridge push - constructive, fresh magma rises, forces plates apart
slab pull - destructive plate margin, gravity acts on denser plate pulls it under

Question 13

distribution of earthquakes

Answer 13

majority form belts along plate margins
some are narrow, sparsely distributed (constructive margins)
denser broader zone on edge of pacific ocean ‘ring of fire’, 80% occur there (destructive margins)
some occur away from plate margins due to human activity (mining, oil extraction)

Question 14

distribution of volcanoes

Answer 14

coincide with constructive and destructive margins
high concentration at ‘pacific ring of fire’
none at conservative, no source of magma
in hawaiian islands crust is thin so magma can break through

Question 15

japan earthquake

Answer 15

march 2011, 9.0 magnitude 100km east of sendai on japanese island of honshu
destructive margin between north american and pacific plate
earth shifted on axis, 3-5 minutes of ground shaking and then tsunami wave took 30 minutes to hit, defences overtopped

Question 16

nepal earthquake

Answer 16

25 april 2015, 7.9 magnitude, 80km north wesr of kathmandu, destructive margin between indo-australian and eurasian plate, 15km below surface, severe ground shaking, landslides, avalanches, caused damages in india, tibet pakistan

Question 17

primary effects of tokoku, japan earthquake

Answer 17

ground shaking causes injuries, deaths, homes, roads, rails destroyed electricity, water and sewage systems disrupted - 4 mil without electricity, 1.5 mil without water

Question 18

secondary effects of tohoku, japan earthquake

Answer 18

10m tsunami - 18000 deaths, 500000 homeless, destroyed port facilities, infrastructure, homes
many without electricity, sanitation, water
explosions at fukushima nuclear plant - fear of radioactive leaks

Question 19

primary effects of nepal earthquake

Answer 19

9000 people died, 20000 injured
3 million homeless
electricity, water supplies, sanitation, communications affected
7000 schools destroyed

Question 20

secondary effects of nepal earthquake

Answer 20

landslides, avalanches - 19 people killed on everest, blocked roads, blocked kali gandaki river, people evacuated at risk of flooding

Question 21

japan: immediate responses

Answer 21

search and rescue teams, people evacuated before tsunami, emergency shelter food and water, roads restored within a few days, power soon restored

Question 22

japan: long-term responses

Answer 22

most debris cleared by early 2015, 2020 - nearly 30000 units of public housing completed (replacing temporary housing), upgraded tsunami warning system launched, sea walls and embankments constructed to protect cities

Question 23

nepal: immediate responses

Answer 23

international search and rescue teams, emergency food kits and shelter material, helicopter rescues, field hospitals from red cross etc.

Question 24

nepal: long-term responses

Answer 24

new national disaster risk reduction policy, most roads repaired by end 2015 UNESCO working with government to restore 700 damaged temples, palaces and museums

Question 25

why do people live in hazardous areas?

Answer 25

cheaper, hazards dont happen often, people may not be aware, volcanoes can bring fertile soil, rocks for building, hot water

Question 26

life near natural hazards in iceland

Answer 26

volcanic rocks used in construction for roads and buildings, hot water from crust provides heat and hot water, eruption of volcano in iceland in 2010 led to surge in tourism

Question 27

monitoring volcanoes

Answer 27

magma rising through a volcano gives warning signs - monitored with seismographs to detect and record quakes, tiltometers for ground deformation, instruments monitoring gas emissions and changes in water chemistry, warnings sent out if eruption seems likely

Question 28

monitoring earthquakes

Answer 28

network of seismometers in japan, warnings issues to public - immediate shelter, trains slow, factories halt - 15 seconds warning in sendai, 2011
buoys detect early tsunami waves

Question 29

predicting volcanoes

Answer 29

scientifically monitoring earthquake activity beneath surface - quite accurate

Question 30

predicting earthquakes

Answer 30

impossible to be accurate - no clear warning signs, study historical records to identify areas at most risk

Question 31

protection from volcanoes

Answer 31

attempts to divert lava flows, buildings designed to withstand collapsing from volcanic ash, tilted roofs prevent build up, window shutters prevent entry

Question 32

protection from earthquakes

Answer 32

infrastructure designed to withstand ground shaking, 400km sea wall built up to 12.5m high to protect cities etc.

Question 33

planning for volcanoes

Answer 33

hazard maps used to help protect 500 million people from eruptions - based on evidence from previous eruptions
predicts likelihood of ash falls, pyroclastic flows, lahars
maps used to control evacuation routes

Question 34

planning for earthquakes

Answer 34

shakemaps show impact of of ground shaking, used to locate high-value developments away from high-risk areas