2. Tectonic Hazards Flashcards
1
Q
What is the structure of the earth?
A
- Inner core (1400km in diameter) - solid made of iron and nickel at 5500 degrees
- Outer Core - 2100 km thick, semi-solid , temp around 5250
- Mantle - 2900 km thick, semi molten, less dense than the outer core
- Crust - oceanic and continental 2 types
1
Q
What are the 2 types of crusts?
A
- oceanic crust - thinner (5-10km) but is more dense and heavier
- continetal crust (older than oceanic as does not subduct) - 25-90 km, thicker but lighter and less dense
2
Q
What is the slab-pull theory?
A
- the movement of plates is due to the subduction of oceanic plates into the mantle and dragging the rest of the plate with it
3
Q
Where do earthquakes occur?
A
- on all plate boundaries
- mainly around the pacific ring of fire
4
Q
Where do volcanoes form?
A
- at constructive or destructive margins
- can also form at hotspots (where columns of magma escape through the crust of the earth)
5
Q
What takes place at a constructive plate boundary and what is an example?
A
- at a constructive plate boundary the plates move apart
- e.g Mid Atlantic Ridge
- make broad and flat shield volcanos
- as magma break through overlying crust shockwaves create earthquakes
6
Q
What happens at a destructive plate boundary and what is an example?
(continental and oceanic)
A
- at a destructive plate boundary plates collide into each other
- when oceanic (Nazca) and continental collide (South American) collide, the oceanic subducts under the continental as it is more dense
- friction causes earthquakes and the melting of the oceanic plate makes magma which breaks through to make a steep sided composite volcano (violent and explosive)
7
Q
What happens at a destructive plate boundary (continental and continetal)
A
- there is no subduction inside 2 plates collide and crust becomes crumpled and uplifts
- causes fold mountains such as Himalayas and formations of mountains cause earthquakes
- no volcanos
8
Q
What takes place at a conservative plate boundary and what is an example?
A
- 2 plates move past each other in opposite directions or the same direction but at diff speeds
- only earthquakes take place due to the friction
- no volcanos
- San Andreas Fault
9
Q
What are primary hazards of volcanic eruptions?
A
- ash
- pyroclastic flow (superheated material travels up to 500 km/h)
- lava flow
- gas emissions (sulfur dioxide, CO2 and water)
- volcanic bombs (rocks ejected by volcano)
10
Q
What are secondary hazards of volcanic eruptions?
A
- Lahars (water mixes with ash to create fast mudflow)
- Acidification (sulphur mixes with water to increase acidity of water)
- Landslides
- Climate Change
- Fires
- Floods
11
Q
What are primary effects of earthquakes?
A
- ground shaking
- gas emissions
12
Q
What are secondary effects of earthquakes?
A
- building collapse
- landslides
- gas leaks
- fires
- soil liquefaction
- subsidence (shrinking of the earths surface)
- mudflows
- tsunami
13
Q
What is some general infomation about Nepal?
A
14
Q
What are primary effects of earthquakes?
A
- caused by the ground shaking, can include death injuries and damage to roads and buildings
15
Q
What are secondary effects of earthquakes?
A
- These are the effects that are the results of primary effects such as tsunamis, fires and landslides
16
Q
Ranking of GDP for Chile and Nepal?
A
- Chile, 38/193
- Nepal, 109/193
17
Q
HDI Ranking for Chile and Nepal?
A
- Chile, 41/187
- Nepal, 145/187
18
Q
Plate Boundary and Magnitude of Chile Earthquake?
A
- Nazca and South American Plate
- Destructive Plate Margin
- 8.8 on Richter Scale
19
Q
Plate Boundary and Magnitude of Nepal Earthquake?
A
- 7.9 on Richter Scale
- 80Km from Capital Kathmandu
- Destructive Plate Margin
- Indo-Australian plate collides with Eurasian
- Shallow Earthquake, 15km below ground
20
Q
Chile Primary Effects (5)
A
- 500 killed
- 12,000 injured
- 800,000 affected
- Port and Santiago Airport badly damaged
- Cost of earthquake is US$30Billion
21
Q
Chile Secondary Effects
A
- 1500km of road destroyed
- Coastal Towns devastated by Tsunami waves
- Fire at chemical plant near Santiago
22
Q
Nepal Primary Effects (6)
A
- 9000 people died
- 8 million affected (1/3 pop. Of Nepal affected)
- 3 Million left homeless (1/8)
- 7000 schools destroyed
- 50% of shops destroyed
- Damage over $5 Billion
23
Q
Secondary Effects in Nepal
A
- Triggered landslides and avalanches
- Avalanches on Mount Everest killed 19 people
- Another Avalanche in Langtang left 250 people missing
- Landslide blocked Kalli Gandaki River
24
Q
What are the 2 types of responses to earthquakes?
A
- Immediate Responses - directly after the event
- Long Term responses - Re-building and reconstruction with aim of returning back to normal
25
Q
Chile Immediate Responses?
A
- Emergency Services acted quickly.
– international help was needed by field hospitals, satellite phones and bridges - Temporary repairs were made to the Route 5 highway which enables aid to be transported rapidly
- Power and Water restored within 10 days
- National Appeal raise $60 Million
26
Q
Chile Long Term Responses
A
- 1 Month after the earthquake, Chile’s government launched a housing reconstruction plan to help 200,000 homes destroyed in the earthquake
- Chile has a strong economy mainly based on copper exports that could be rebuilt without much foreign aid
- President announced Chile would be fully recovered in 4 years
27
Q
Nepal Immediate Responses?
A
- Search and Rescue and Medical Support quickly arrived from countries such as India
- Helicopters delivered supplies to cut off villages and helped those trapped in avalanches
- Half a million tents provided
- Field Hospitals set up to avoid overcrowding
- Many countries pledged financial aid
- 300,00 people migrated away from Kathmandu to friends + family
28
Q
Nepal Long Term Responses?
A
- Roads repaired and landslides cleared
- Stricter building codes
- Tourism was boosted in July 2015 by major heritage sites being reopened
- 7000 schools to be re-built
29
Q
What are some reasons why people live in areas at risk?
A
- fertile soils near volcanos due to minerals so crop yield are higher here
- tourism, people want to visit these areas so jobs are more readily available
- minerals and precious stones can be mined in these areas
- areas can be used to produce geothermal energy
- people in poverty may have pressing issues
- social reasons such as family land
30
Q
What are the 4 management strategies to reduce risk of tectonic hazards?
A
- monitoring
- prediction
- planning
- protection
31
Q
How can tectonic hazards be monitored?
A
- volcanos can be monitored using:
1. Seisometers (detect tremors)
2. remote sensing (satellites detect heat increases inside volcanos)
3. gas sensors (detect increases in gases such as sulphur and radon that are released before eruption) - earthquakes can be monitored using:
1. Seisometers (detect foreshocks)
2. gas sensnors (apparently radon released before earthquake)
32
Q
How can tectonic hazards be predicted?
A
- volcano monitoring allows accurate predictions of eruptions so evacuation and exclusion areas can be put in place
- earthquakes are impossible to predict at all
33
Q
How can tectonic hazards be protected against?
A
- VOLCANO around volcanos exclusion and evacuation zones can be set up
- stregnthening of roofs to support falling ash weight
- EARTHQUAKES: earthquake drills
- earthquake resistant building design such as shutters on the windows
- sea walls to protect against Tsnunami
34
Q
How can tectonic hazards be planned for?
A
- (both volcanos and earthquakes)
- hazard mapping and risk assesments to identify those most at risk (so people can be moved and building stopped)
- evacuation plans and stockpiles can be made
- emergency services can be trained
