Tectonic Processes and Hazards

Question 1

What process is now widely thought to be the main driver of plate tectonics?

Answer 1

Slab Pull

Question 2

Define the term hazard

Answer 2

A perceived natural/geophysical event that has the potential to threaten both life and property.

Question 3

How can governance increase vulnerability?

Answer 3

Poor building regulations can result in higher levels of building collapse.

Question 4

Whilst the world may appear to be becoming more hazardous, identify reasons why we must be cautious when looking at data on disaster trends.

Answer 4

-Better recording of events may make it appear that there are more events occurring.
-There are more people living in areas exposed to natural hazards and therefore more casualties may occur.

Question 5

Name the stages of the hazard management cycle

Answer 5

Prevention and mitigation, preparation, response, recovery.

Question 6

Where and why do earthquakes happen?

Answer 6

95% of earthquakes occur along plate boundaries-when plates move against each other, they sometimes stick, causing huge amounts of pressure to build up. When pressure builds too much, rock fractures along faults and energy is suddenly released as seismic waves.
The other 5% are intra plate earthquakes

Question 7

what instrument is used to record data about seismic waves?

Answer 7

seismograph

Question 8

what info can scientists get from seismic waves?

Answer 8

earthquake behaviour and the earth’s structure

Question 9

what are the two main classifications of seismic waves and how are they different?

Answer 9

Body waves-travel through earth
surface waves-travel along earths surface

Question 10

What are P waves and how do they travel through the earth?

Answer 10

primary/pressure waves.
travel through solids, liquids and gases
compress and expand the Earth’s surface in the direction of wave travel

Question 11

what are S waves and how do they travel through the earth?

Answer 11

secondary/shear waves
they can only travel through solids
they create an up and down motion, perpendicular to the direction of wave travel

Question 12

what are Love waves and how do they move through the Earths surface?

Answer 12

surface waves that travel slower but are larger and more destructive
perpendicular to wave travel and create a side-to-side motions
they are the fast moving of the two surface waves and can only travel through solids

Question 13

what are Rayleigh waves and how do they move through the Earth’s surface?

Answer 13

surface waves that create an elliptical motion
they are the most spread-out waves but, creating long durations on seismographs
they are the most destructive of them all and are what most people can feel
they can only travel through solids

Question 14

primary effects of seismic waves

Answer 14

ground shaking, crustal fracturing

Question 15

secondary effects of seismic waves

Answer 15

liquefaction-violent shaking causes rocks to lose strength and become more liquid than olive. subsoil loses its ability to support infrastructure making rescue efforts more difficult
landslides and avalanches- ground shaking places stress on slopes, so they fail
tsunamic- ground underwater shakes, displacing water above.

Question 16

Christchurch liquefaction- details od events

Answer 16

1. 4/9/2010 (magnitude-7.1)
2. 22/2/2011 (magnitude 6.2)-caused casualties
3. 13/6/2011 (magnitude 5.3 and 6.0-80 mins apart)
4. 23/12/2011 (magnitude 5.8 and 5.9- 80 mins apart)

Question 17

Christchurch liquefaction- geological and ground conditions

Answer 17

-Christchurch sits on deep alluvial (fine soils) of the Canterbury Plains, except for the southern edge that is located on the slopes of the Port hills of Banks Peninsular.
-Plains cover 50km wide and 160km long area. Made up of very thick soil deposits from east flowing river.
-The area was originally a swamp-sand and silt
-shallow soils, surface soil on west edge thinnest, thicker at Christchurch. soft wet sediment.
-Groundwater level relatively high across the city:
-water table 5m deep in Western suburbs
-shallower towards the east until it reaches ground surface

Question 18

Christchurch liquefaction-other factors increasing risk

Answer 18

-sparsely developed-more susceptible to damage
-difficult relief of the land-longer time for aid to reach settlements
-alluvial soils
-abundance of water systems
-flooding of river
-densley populated-falling buildings
-timber framed buildings
-multiple earthquakes in short time period

Question 19

Christchurch Liquefaction-impacts of liquefaction

Answer 19

-extensive damage to properties
-large volume of sand/silt ejecta covering buildings
-massive sand boils (indicates very severe and extreme liquefaction of very loose soil)
-mud and water flooding streets
-permanent tilt of houses, foundations, and structural damages
-damage to buried pipe networks
-damages to bridges-lateral spreading of riverbanks
-20,000 residential buildings severely affected
-8,000 residential buildings damaged beyond repair

Question 20

Kashmir Landslides-details of events

Answer 20

8/10/2005
magnitude 7.6 earthquake triggered several thousand landslides
epicentre near cities of muzaffrabad

Question 21

Kashmiri landslides-location

Answer 21

karli and tang valley, Jhelum river valley, dana hill: very mountainous, steep relief, tight meanders
near bodies of water: tang reservoir, tang stream, karla stream
around 30-40km from Rawalkot airport

Question 22

Kashmir landslides-other factors increasing risk

Answer 22

sandstone, silt stone, mudstone, clay and limestone; easily eroded, not as condensed, or well held together. soft material dammed rivers=floods
weak rock type
shear valleys
proximity to settlements
proximity to water sources
remote location-long time for aid to reach
level of development

Question 23

kashmir landslides-impacts of landslides

Answer 23

flooding that will endanger most residents in the village of Haitian
damage to bridges
destroyed houses

Question 24

Japanese prevention and preparation strategies

Answer 24

Structures built to become more flexible if hit by a tremor; some are built on Teflon which allows buildings to move with the shock
Phone updates- every smartphone is installed with an earthquake and tsunami emergency alert system- triggered around five to ten seconds prior to impending disasters (potentially not enough time to seek protection if needed)
Awareness and education on disaster prevention-schools in Japan run regular earthquake drills. young schoolchildren are educated on the best way to seek protection and stay safe if an earthquake hits their area. they also attend earthquake simulators so they can identify the feeling of an earthquake.

Question 25

2011 Tohoku earthquake and tsunami

Answer 25

March 11th 2011, Japan experienced strongest earthquake in its recorded history (magnitude 9.0-9.1) which cause 19,759 deaths and 6,167 injuries.
the Tohoku earthquake caused a tsunami and caused the meltdown of 3 nuclear reactors at the Fukushima Daiichi Nuclear Power Plant which released toxic, radioactive materials into the environment and forced thousands of people to evacuate their homes and businesses.
used to suggest that even with large amounts of preparation and prevention strategies, it can be impossible to effectively prepare for significant hazard events.

Question 26

eyjafjallajokull eruption

Answer 26

volcano started to erupt in mid-march following several months of seismic activity in Iceland
started on north-east flank but eventually moved to the centre of the volcano with a 3km wide crater surrounded by ice- ice started to melt and glacial water began flooding the volcano (jokulhlaup)
large plumes of volcanic ash spread above the volcano and moved eastwards with the jet stream towards Norway and Northern Scotland.
closed European airspace as a safety precaution and airlines lost an estimated £130 million everyday that airspace was closed.
not a significant eruption, but was significant in its impacts in comparison to other eruptions

Question 27

Haiti earthquake 2010

Answer 27

magnitude 7.0 in port au price
220,000 people died
29 million metres of rubble and debris in Port au Prince
1.5 million people living in camps at its peak
difficult getting aid to the area because of poor management of the situation
industries were significantly affected
mainly linked to the ineffective management due to the development of Haiti: aid from other countries was essential

Question 28

montserrat eruption

Answer 28

experienced a major eruption in 1997 in which 50% of the population were killed. however their population consisted of 38 people which meant that their deaths were significant for their country, but not on a global scale. would this eruption have been as significant if the island was bigger, more developed and had a higher population?

Question 29

Destructive plate boundaries landforms

Answer 29

Continental/Oceanic:
-Earthquakes
-Volcanoes
-Fold Mountains
Oceanic/Oceanic:
-Volcanoes
-Earthquakes
-Island Arcs
-Ocean trenches
Continental/Continental:
-Earthquakes
-Fold mountains

Question 30

Conservative plate boundaries landforms

Answer 30

Earthquakes

Question 31

risk

Answer 31

a location that will be more likely to experience a tectonic disaster

Question 32

disaster

Answer 32

when a location has had greater impact from a tectonic hazard. this could be a large number of deaths, buildings destroyed or amount of people affected.

Question 33

intra-plate earthquakes

Answer 33

pre-exiting weaknesses are reactivated to form seismic wave and an earthquake event in the middle of a tectonic plate.

Question 34

volcanic hotspots

Answer 34

they are among the centre of plates. its a localised area of the lithosphere with an unusually high temperature due to upwelling and hot molten material.

Question 35

where do earthquakes occur?

Answer 35

they start at the hypo centre with the focus directly above at the Earth’s surface.

Question 36

where do volcano formations occur?

Answer 36

majority are at plate boundaries, moving tectonic plates (towards or away), magma rises to fill gap.
other 40% of volcanoes don’t occur at plate boundaries. hotspots; deep below surface that melt the plate and creates magma at top of plate.

Question 37

lithosphere

Answer 37

the uppermost layer of the Earth. thinnest, least dense, lighter. 7km (Ocean)- 70km (continental) thick.

Question 38

mantle

Answer 38

composed of silicate rocks that are rich in iron and magnesium. semi-molten and temperature gradient generates convection current; cause mantle circulation and could contribute to plate movement.

Question 39

Outer core

Answer 39

dense, semi-molten rocks, nickel and iron alloys.

Question 40

inner core

Answer 40

similar composition to outer core, solid due to extreme pressures. Radiogenic heat and primordial heat.

Question 41

convergent boundaries

Answer 41

two plates push into each other; ocean-ocean, oceanic-continental, continental-continental.
Continental-continental; neither plate subducts- sediments between them are crumpled (they form mountain ranges).
Oceanic-Oceanic; subjected plate melts; magma forms underwater volcanoes (form island arcs).
Oceanic-Continental; friction causes earthquakes, volcanic eruptions, most active seismically.

Question 42

Divergent boundaries

Answer 42

Two plates move away from each other. New crust is created by magma pushing up from the mantle (seafloor spreading).

Question 43

Transform boundaries

Answer 43

two plates slide past each other horizontally. (San Andreas fault).
No crust is made or destroyed, it is tectonically active. Plates sometimes stick, pressure builds up and causes a strong shallow-focus earthquake.

Question 44

Continental Drift

Answer 44

Alfred Wegner suggested that continents seemed to fit together and developed ‘The Theory of Continental Drift’ as a result. continents can drift apart from each other and all separate continent were once joined together.

Question 45

Sea Floor Spreading

Answer 45

Continental drift was achieved through ‘sea Floor Spreading’. New oceanic lithosphere is created as older materials are pulled away. the sea floor spreads apart and magma rises to fill gaps.