Challenges of natural hazards - teconic hazard

Question 1

What is the eraths structure?

Answer 1

the earth is composed of 4 main layers:
-The inner core which is a dense solid layer which is under a ot of pressure. Composed of iron and nickel. Temp around 5500 degrees
- The outer core which is a semi molten layer with temps around 5000-5500 degrees
- the mantle which is a semi molten layer that surrounds the core. The upper portion of the mantle is a weak layer called the asthenosphere which can deform like plastic
- teh crust is the outermost layer of the earth and there are 2 types: oceanic and continental crust

Question 2

what is the difference between oceanic and continental crust

Answer 2

-Oceanic crust is thinner but much heavier and denser than the continental crust hense why it is the one which subducts and is constantly getting destroyed. It is formed by basaltic rock.
- continental crust is older but thicker and lighter than the oceanic crust because it is not destroyed.

Question 3

What is the rigid shell on the surface of the earth formed by the upper mantle and crust called?

Answer 3

lithosphere

Question 4

Tectonic plates are broken fragrements of what?

Answer 4

lithosphere

Question 5

what is the name given when 2 plates meet?

Answer 5

plate margin

Question 6

what are the 3 main types of plate margins>

Answer 6

destructive, conservative and constructive

Question 7

what are each of the plate margins?

Answer 7

-Destructive: It can happen between 2 continental or one of each.
If 2 continental plate margins colide, there is no subduction due to no difference in density. Insead they become crumpled and uplifted with pressure between the 2 plates, this results in the creation of fold mountains. This collision causes earthquakes but no volcanic erruptions due to no magma present
If one of each crust collides, the oceanic crust subducts under the continental crust. This causes the pressure of magma to build up and force its way up through the cracks of the rocks and rises up through composite volcanoes. Causing colcanic erruptions and easrthquakes.
- At a conservative plate margin, the plaate move past each other in the same direction but at different speeds or in opposite directions. They form earthquakes but not volcanoes.
-contructive plates are when 2 plates move away from each other and when the plates move apart, magma rises between the gapes which then pours onto the surface and the lava dries up, forming volcanoes. Earthquakes can also happen due to the vibration when the plates move apart. This process can happen both on oceanic and continental crust.
On land, they can form steep sided rift valleys and in oceans, new land can be formed and this is known as sea floor spreading.
At the same time volcanoes form on constructive plate margins but wekaer erruptions happen becasue the magma barely reaches onto the crust.

Question 8

why do conservative plate margins cause earthquakes?

Answer 8

when the sliding happens, pressure builds up between the plates and eventually it becoems so large that the plate moves ina. sudden jolt and the plates slip and shift, causing large amounts of energy to be released and this sends vibrations through the grounds and causes an earthquake. On an oceanic crust or in the ocean, this can displace large amounts of water and create tsunami. No volcaoes are formed as no magma is generated and no gaps for the magma to rise.

Question 9

Why are both earthquakes and volcanoes found on destructive plate margins?

Answer 9

As the plates colide, pressure builds up and eventually the rocks fracture and causes an earthquake . Similarly, when the oceanic crust subducts it leaves a deep ocean trench and causes part of the mantle to melt, creating magma. The magma rises and creates pressure with some eventually errupting out of the surface producing a linear belt of volcanoes. This causes violent erruptions.

Question 10

what is a tectonic hazard?

Answer 10

the threats that are caused by the movement of tectonic plates that have the potential to cause damage to life, property and the environment.

Question 11

What are the 2 theories responsible for the movement of tectonic plates

Answer 11

Convection and slab pull and ridge push

Question 12

what is the convection currents.

Answer 12

when plates move due to the movent of the magma which creates convection currents. The cores temp casues hotter and less dense magma to rise and the sink back down towards the core when it reaches the top and becomes cooler (denser) However there has only be limit evidence supporting this

Question 13

what is the slab pull ridge push

Answer 13

this is the process which drives the mantle convection instead of the other way around.
During ridge push, the plate moves apart and the magma rises. Then the magma cools and forms new plate material. It becomes denser as it cools and slides away from the ridge, causing plates to move away fro each other.
During slab pull, the denser plate sinks back into the mantle due to gravity and pulls the rest of the plate with it.

Question 14

General distribution of earthquakes and volcanoes

Answer 14

• occurs on plate margins.
• earthquakes and volcanoes can be found both on land and sea
• earthquakes can be found along all types of plate margins but volcanoes can only be found on destruction and constructuve plate margins.
  -Large band of earthquake and volcanoe circling the pacific plate is the ‘ring of fire’
  -The belt of volcanoes throigh the mid alantic ocean is called the mid alantic ridge

Question 15

what are the effects and responses of tectonic hazards?

Answer 15

Primary effects =P
Secondary effects =S
effects:
-intense shaking of ground (P)= tsunamiis (S)
-injuries and people being killed (P)= trauma and loss of income as peoples livlihoods are destroyed (S)
- Infrastructire destroyed (P) = homlessness and social disorder/conflicts (S)
responses:
1) immediate:
- providing food and water

Question 16

what are the case studies for tectonic hazards?

Answer 16

japan (Tohoku) and Haiti

Question 17

Generall stuff for the Japan earthquake:

Answer 17

• destructive plate margin
• epicentre was just 130km off teh coast nearest to sendai and miyagi province
• 9.1 ritcher scale
  -1 million homes destroyed and caused over 300 thousand to become holeess
• nearly 16000 died
• Tsunami happened 20 min later
• NE coast line dropped 60km
• Fukushima nuclear power plant almost in melt down
• 300billion in damage
• clear plans of response to earthquake due to good preperations
• temporary housing immediate constructed
• 250 billion in new strategic recovery plan
• 5 year recovery plan

Question 18

generall stuff for haiti:

Answer 18

7.0 ritcher scale but teh earthwauke happened much closer to the surface of the earth (less than 12 km)
- more than 1 million homless
- 31thousand died
- 13 billion property damage
- make shift towns had no running water and wate disposal system
- mass graves and outbreak of cholera
- damaged communication = slow down aid = violence
- people were confused of who was in charge
- 80% rubble still not cleared after 6 months

Question 19

why do people loive in hazourdous areas?

Answer 19

1) Geothermal energy
In volcanic areas gerotehrmal energy is a major source of energy/electricity. It is renewablw and will reduce greenhouse gases.
2) Mining:
Provides many jobs but is very dangerous.
Minners provided little protective clothing, Hydrogen sulphide and sulfur dioxide gas burn their eyes and throat
3) unworthy/infrequency:
- Major advancements like developement of warning systems allow some people to feel safe to stay.
4) developeemnt: Better buildings
5) Poverty = no choice not to live here
6) Lack of education

Question 19

How are the 4 management strategies in pl;ace?

Answer 19

1) monitoring:
Using scientific equipment to detect signs. Volcanologist and seismologist monitor changes in the surrounding area. Earthquakes are hard to monitor because they usually do not display warning signals.

2) Protection:
enhance the protection and stability of a building to reduce damage from earthquake (technically cant prevent damage from volcanoe erruption).
Eg.
- walls reinforced with steel and concrete to reduce movemtn
- autoatic shutters that come down to prevent broken glass from falling
- rolling weight on rof to conterct the shock waves
- shcok absorbers to absorb ground shaking
3) Prediction:
Predcition of volcanoes are based on the monitoring factors but there are no esact way of predictinga. earthquake. It is said that if an earthquake has not happened in a long time, the next one will be more intense because more pressure has been building
4) Planning:
hazard maps are produced to identify the areas most at risk to help see what important buildings have to be built away. (applies mostly to volcanoes)
Planning for earthquake include:
Preparing emergency supplies
-drills
- fastening down objects to reduce number of them from falling

Question 19

What are the 4 main types if manegemnt strategies?

Answer 19

Monitoring, predicting, protection and planning

Question 20

At some places in the earth’s system of tectonic plates, new crust forms and the plates move away from one another. When this happens under water, it is called a mid-ocean __________. What word completes the sentence?

Answer 20

“ridge”

Question 21

One theory is that tectonic plates move due to convection currents.Based on this theory, as the lower layers are heated by the earths mantle, do they become more or less dense?

Answer 21

Hotter liquids and gases expand, become less dense and rise. A good example is the air in a hot air balloon.

Question 22

How can you monitor volcanoes?

Answer 22

1) seismic waves:
- Seismic waves can be used to scho if a volcanoe is getting ready to erruppt. Many volcanoes experience an increasing intensity in frequency an size of earthquakes as they prepare to errupt.
We can monitor this by using seismonitors whih produce seismographs.
2) monitoring ags emissions:
- As magma rises into the magma chambers, gases escape. One of the main gases is Sulphur dioxide and if the quantity in this gas is increasing, then it could signal a sequence of erruptions comming.
3) Ground deformation:
- The movement of magma within the crust can deform the ground above. For example, a volcanoe can swell. If a volcanoe swells, it could mean that magma has collected near the surface. Scientist that monitor an active volcano will usually measure the tilt of the slope and track the changes in the rate of swellling.
4) Satilite images and remote sensing:
- Remote sensing is the use of satilites to detect things about the earths surface. This is usefull for monitoring any changes in volcanoes at the surface. Similarly, satilites can monitor the heat or thermal activity of the volcanoe to check for upwelling of magma.
- We can also check for escaping Sulphur dioxide using gas sensing
- Finally looking at before and after images of the ground can tell if teh ground is deforming

Question 23

How can we monitor earthquakes?

Answer 23

1) seisometers:
- ???
2) Animal behaviour:
-Many observations have shown that animals react to an earthquake before it happens.
3) laser beams:
- They have been used to detect plate movement by directing the beam across a fault line.

Question 24

How many times largher is a step up on a ritcher scale?

Answer 24

10
This means that a earthquake at 4.0 is ten times larger than one at 3.0

Question 25

what is the difference between the mercalli scale and ritcher scale?

Answer 25

The mercali scale is a measure of the intensity of the earthquake by looking at the effects it has on the population and environment. It is measured from 1-12
The ritcher scale is a measure of teh energy released/strength of the earthquake. It is a measure from 1-10