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Geography - Tectonics (Year 1) > EQ1 > Flashcards

EQ1 Flashcards

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1
Q

Why has the recorded number of earthquakes and volcanic eruptions increased?

A

More sophisticated methods of recording disasters have been invented, which means constant monitoring of hazards.

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2
Q

What are three key theories of tectonics?

A

1596 - Abraham Ortelius the mapmaker observed that the edge of south America matched with Africa, and North America with Europe.
1920 - Alfred Wegener proposed the theory of Pangea, the idea that all of the continents were once one, and they moved away from each other over thousands of years.
1960’s: The US was nervous about Russian nuclear testing, so they planted 120 seismometers globally, and they stated mapping seismological events.

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3
Q

Give an explanation and example of a convergent boundary on two continental crusts:

A

Crumpling will occur from two continental crusts converging, as their density is too light to sink. This has occurred at the Himalayas in Nepal.

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4
Q

What is the theory of Pangea, and who developed it?

A

The theory that 225 million years ago, all of the continents fit together into a supercontinent. Alfred Wegener developed this theory in the 1920’s.

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5
Q

Who finalised Wegener’s theory of Plate Tectonics?

A

Int eh 1960’s, Harry Hess developed the theory of mantle convection.

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6
Q

Who are the most vulnerable to hazards?

A

Peoeple who live off less than $2 a day. This is more than 2 billion people on the planet.

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7
Q

How is the population meant to increase by 2050?

A

Meant to increase to 9.7 bil.

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8
Q

Why was the earthquake of Kathmandu so disastrous?

A

The epicentre was less than 80km from the capital of Nepal in 2015. This meant 10,000 died.

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9
Q

What is an example of a major plate?

A
  • African plate
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10
Q

What is an example of a minor plate?

A

Cocos

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11
Q

What is an example of a micro-plate?

A

Sunda

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12
Q

What are all of the intra-plate processes?

A
  • Ancient faults - Rhine Rift Valley
  • mantle plumes - Nyiragongo
  • hotspots - Hawaii
  • upwellongs beyond a concergent collision zone - Himalayas
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13
Q

What are the processes which shift a tectonic plate?

A
  • convection currents - Made of peritotite
  • slab pull - cold spots cause dense rock to push doen (Pacific plate)
  • mineral composition - Helium and Olivine
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14
Q

What does palaeomagnitism prove?

A

The direction of magnetism within rock changing proves seafloor spreading. it also proves the radiation which protects the earth from solar radiation.

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15
Q

What is the crust?

A
  • 7-70km thick.
  • Solid
  • Can pass body waves through it.
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16
Q

What is the mantle?

A

700-2900 km deep. Can pass body waves through it. Is solid and liquid.

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17
Q

What is the outer core?

A

2900-5200km deep.
Only P waves can travel through it.
Liquid and magnetic.

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18
Q

What is the inner core?

A

5200 - centre km deep.
Shadow zone from P waves is created from 105-140 degrees.
Solid + emmits radiation

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19
Q

What is a destructive boundary, and where is it?

A

The Chile/Peru Trench:
- SA plate and Nazca Plate.
- Volcanoes 100km from the plate boundary (Intra-plate process)

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20
Q

What is a constructive boundary, and where is it?

A

Nazca + Pacific Plate:
- Submarine volcanoes which become islands.
- has undersea ridges.

21
Q

What is a conservative plate, and where is it?

A

10,000 quakes a year created by the San Andreas Fault.
Pacific and North American Plate

22
Q

What is moho?

A
  • The boundary between the crust and the upper mantle.
23
Q

what is bathymetry?

A

The study of beds or floors to water systems.

24
Q

What evidence is there for plate tectonic theory?

A

Continental shapes
matching fossils
matching rock type
tectonic hazards form around plate boundaries.

25
Q

How far can foci reach in depth?

A

700km

26
Q

What is a Rayleigh wave?

A

A wave which moves in a rolling motion.
Results in the most shaking felt by people.

27
Q

Why is the Benioff zone where fractures occur?

A

friction from where plates try to pass each other, and creates tension.

28
Q

What was the largest quake caused by a destructive boundary?

A
  • 1960 Chile Earthquake which had a 9.5MM measuring.
29
Q

What was the largest quake caused by a conservative plate boundary?

A
  • 1992 San Andreas Fault 7.6MM measuring.
30
Q

What was the largest quake caused by a constructive plate boundary?

A
  • 2000, Iceland with a 6.5MM measuring. (These tend to be smaller due to the motion of plates)
31
Q

What are the secondary hazards caused by a volcanic eruption?

A
  • Lahars
  • Jokulhlaups
32
Q

What are the secondary hazards caused by an earthquake?

A
  • Tsunamis (Tohoku 2011)
  • Liquefaction (Christchurch 2010)
  • Landslides (Kashmir 2005)
33
Q

What causes shifts in rock?

A

Unconsolidated sediment loses cohesive strength and moves downslope via gravity.

34
Q

Case Study: Christchurch 2010 earthquake

A
  • 6.5MM earthquake
  • 5.9km focus
  • 80% of CBD buildings were damaged.
  • Soft, horizontal layers of rock slapped back down causing further reverberations.
  • 185 deaths.
35
Q

Describe the retrofitting in Christchurch 2011:

A
  • New buildings have to have stone columns installed 10m below foundations.
  • These buildings have been tested against 6.0MM waves and have remained integral.
  • The clock tower had steel reinforcements which allows is to rock.
36
Q

What do we need to consider when assessing the effectiveness of retrofitting?

A
  • It has been used in Christchurch.
  • New Zealand is a developed country.
  • Suburbs are likely to be less protected due to the higher responsibility of individuals.
37
Q

Case study: Tohoku tsunami of 2011

A
  • 3-10m wave height in some areas.
  • 18,000 deaths in Honshu, Japan.
  • $220 billion in damages.
  • 127,000 houses destroyed.
38
Q

What is an extrusive feature?

A

A landform created through the ejection of material from the centre of the earth from magma forming into lava.

39
Q

Give an example of an ancient supervolcano:

A

Yellowstone eruption 2.1 million years ago was 6000 times larger than Mt. St. Helens eruption of 1991.

40
Q

What is basaltic lava?

A
  • hottest
  • 0.5-2% gas content
  • 50% silica content
  • thin and runny
  • Found at shield volcanos and hotspots.
41
Q

What is andesidic lava?

A
  • 800-1000 deg.
  • 3-4% gas content
  • 60% silica content
  • intermediate viscosity
  • composite cone volcanoes
42
Q

What is Rhyolitic lava?

A
  • coolest - 650 - 800 deg.
  • 4-6% gas content
  • 70% silica content
  • thick and viscous
  • cone volcanoes. (Stratovolcanoes)
43
Q

Which type of volcano is more dangerous?

A

Cone volcano (Strato volcanoes) Are more dangerous than shield volcanoes.

44
Q

what is a Phreatic eruption?

A

An eruption which contains steam or gas emmission.

45
Q

Case Study: Eyjafjallajukoll 2010

A

jokulhlaups formed by glacial deposits.
tephra emitted into the Trans-Atlantic Airline which delayed 100,00 flights.
Breaches were made in the defences against water to prevent damaged.
Was not located to any densely populated areas.

46
Q

Case study: Montserrat 1997

A

Plymouth was destroyed by pyroclastic flows.
Farmers did not leave, as they were worried about abandoning their farms. As a result, 12 people died.

47
Q

Case study: Mt. Merapi Indonesia 2010

A

350,000 people had to be rescued from mountain side due to population pressures.

48
Q

Case study: Nyiragongo 2021 eruption

A

DRC:
400 people were killed by 60km/h lava flows in the middle of the night. (1991)
350 people were killed in 2021.
17 nearby villages were badly affected by the flowing lava, which destroyed hospitals, schools, and homes.

49
Q

Case study: Pinatubo 1991

A

20 million tonnes of sulphur dioxide was emitted into the atmosphere. Cooled the earth by 0.6 degrees for 3 years.

Geography - Tectonics (Year 1) (4 decks)

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