Harzardous Earth Flashcards

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1
Q

Explain the evidence that support plate tectonic theory.

A

Jigsaw Fit: The east coast of South America and the west coast of Africa look like they once were connected.

Convectional Currents: hot rock rises in the mantle and then moves in two different directions, which pulls the crust apart. The hot rock, then sinks and gets cooler and brings parts of the crust down, pulling the plates apart.

Study of Fossils: The Mesosaurus fossils were found on the eastern coast of South Ameirca and the western side of Africa. This means that they died in each land then the land split and left the fossils behind distributed across each continent.

Geological Patterns: Identical rocks and mountain ranges I found over the ocean in the continents, meaning they once got torn apart. Glacial striations have also been found in continents that are now warm which means that they could have been connected to Antarctica. Coal has also been found in cold places which must have happened in hot areas, so the continents must have connected up with these geological patterns.

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2
Q

Why are volcanoes and earthquakes found along plate boundaries?

A

Because all along plate boundaries, the plates are causing stress and friction which is then released to form earthquakes. All while, in subduction areas, magma is building up in the magma chamber due to the melting of the oceanic plate creating magma, which is ready to force its way through a composite volcano.

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3
Q

How do earthquakes and volcanoes occur at convergent/destructive plate boundaries?

A

Convergent/destructive plate boundaries are the result of a continental plate and an oceanic plate colliding with each other. The oceanic plate is then forced beneath the continental plate. As the plates move against each other friction and stress builds up and when this is finally released an earthquake occurs. Lighter continental crust remains at the surface but crumples into fold mountains, the sediment and water from the continental plate melt in the mantle and form magma and fill the magma chamber. Then magama builds up in the magma chamber and when the pressure builds up the magma escapes through a weak spot which then becomes a composite volcano because the sediment makes the magma viscous so it doesn’t go far creating a tall steep composite volcano.

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4
Q

How do earthquakes and volcanoes form at divergent plate boundaries?

A

Divergent: convection currents in the mantle drive the plates away from each other and new mantle rises along the opening and creates new crust creating a volcano. The crust is then pulled apart where cracks and faults are made which causes earthquakes. Where the hot mantle cools and falls, it drags the plates down with it creating subduction zones.

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5
Q

How do earthquakes form at conservative plate boundaries?

A

Conservative: The plates move sideways past each other in a series of jerks. Huge stress is developed in the rock and the plates can lock together due to friction. When this lock is broken the stress is released and this causes and earthquake.

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6
Q

How do earthquakes form at collision plate boundaries?

A

Collision: When two continental plates collide they both rise as they are the same density. This causes fold mountains to grow when they push together. As the plates push togehter even more they lock together due to friction but when this friction is overcome earthquakes occur due to the stress being released.

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7
Q

What were the effects of the Monserrat volcano eruption?

A

Lava flows - slow moving magma which destroys everything in its path.
Lava explosions - solidified lava fragments which have been made from magma solidifying creating large lava domes over the volcano which then breaks up when it erupts causing the lava fragments to fall down the mountain.
Pyroclastic flows - fast moving currents of hot gas and rock which move downhill. The pyroclastic flows from Montserrat travelled up to 4km.
Volcanic ash - fragments of lava which are lifted high into the atmosphere and travel great distances in the wind. The wind blew the volcanic ash initially to the south west of Montserrat but it ended up and travelling to the atlantic.
Volcanic bombs - mass of molten rock larger than 64 mm in diameter, formed when a volcano ejects viscous fragments of lava during an eruption which travel many kilometers.
Lahars - mudflow made up of pyroclastic material, rocky debris and water which is hot and travels fast down the side of a volcano even after the eruption has ended.

Overall, the Montserrat had effects on land all around the volcano and more than 15 settlements were destroyed, which were around 4km away from the volcano.

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8
Q

Why did human and physical factors caused the Haiti earthquake to be so destructive?

A

It was so destructive because:
The magnitude of the shock waves were 7 on the Richter scale.
The depth of the focus was only 8-10 km deep which meant that the earthquake was felt at the surface more causing more destruction.
The location of the epicentre was only 15 km southwest of Port-au-Prince ehich means that it was very close to the capital meaning lots of damge happened on land.
People weren’t prepared as they didn’t get any early warnings as people couldn’t predict it.

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9
Q

How do tsunamis form?

A

Subduction occurs causing stress on the boundary and the flexing of the plates can cause an earthquake. The plates will suddenly flick past each other and release all of their energy in the waves. As the waves reach the shallower water they will get closer together, taller and slower. The waves move in different directions like a ripple. The tsunami then surges very far inland picking up anything in its way causing mass destruction.

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10
Q

Name the order of the layers of the earth from outer to inner.

A

Crust
Mantle
Outer core
Inner core

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11
Q

What is the crust?

A

Thinnest layer, coldest layer, solid rock

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12
Q

What is the mantle?

A

Thickest layer, 1000°c near the crust 3700°c near the outer core, solid rock that can flow (semi-molten)

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13
Q

What is the outer core?

A

Approximately 2300km thick, between 3700°c and 5000°c, semi liquid iron.

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14
Q

What is the inner core?

A

Very dense, hottest part of the earth (5000°c), mainly iron and nickel, it is solid due to the pressure.

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15
Q

Name the different tectonic plates.

A

On GoodNotes

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16
Q

What features do Divergent plate boundaries cause?

A

Volcanoes
Earthquakes

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17
Q

What features do Conservative plate boundaries cause?

A

Earthquakes

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18
Q

What features do Collision plate boundaries cause?

A

Fold mountains
Earthquakes

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19
Q

What is an earthquake?

A

Earthquakes are vibrations of the earth’s crust caused by movement at plate boundaries and major fault lines. Earthquakes can occur at all major fault boundaries but the most severe are usually conservative and convergent.

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20
Q

What is a fault?

A

A fracture between two blocks of rock on the earth’s surface.

21
Q

What are shockwaves?

A

Shockwaves are released from the focus.
Primary waves - forwards and backwards, quickly
Secondary waves - sideways and up and down, slower

22
Q

What is the epicentre?

A

The point in the earth’s surface directly above the focus of an earthquake.

23
Q

What are volcanoes?

A

Volcanoes are openings or cracks on the lithosphere where the magma from inside the Earth can escape onto the surface. Molten hot rock under the earth’s surface is called magma but when it is on the earth’s surface it is called lava.

24
Q

What is an active volcano?

A

Liable to erupt

25
Q

What is a dormant volcano?

A

A volcano which hasn’t erupted for many years.

26
Q

What is an extinct volcano?

A

A volcano which has not erupted for many thousands or millions of years.

27
Q

What is a supervolcano?

A

A volcano 1000x times bigger than a regular volcano that has potential to produce an eruption with major effects on the global climate and ecosystem.

28
Q

How are composite volcanoes formed?

A
  • Millions of years ago, magma from a magma chamber forced its way up through a weak spot in the earth’s surface.
  • The lava then cools and turns into rock, then many years later the lava forces its way up again.
  • This process repeats over and over, every time the laver cools creating a new layer of rock on top of the previous layer.
  • Over millions of years this process continues with new layers being added which creates a volcano.
  • Every time the volcano erupts, ash and steam are spewed our of the volcano and the ash settles on the volcano and cements into rock.
29
Q

What does PPP stand for?

A

Predict, protect, prepare

30
Q

What are four things you could do to a building to make it more resistant to earthquakes?

A

Add X-bracing, make it a tall building, add counter-weights, add shock absorbers

31
Q

What are convection currents?

A

Hot rock rises in the mantle and then moves in two different directions which pulls the crust apart. The hot rock then sinks and gets cooler and brings parts of the crust down which creates deeper areas. They are important because they drag the earths plates apart creating volcanoes, they also create subduction zones that also create earthquakes and volcanoes.

32
Q

What is the Richter scale?

A

The Richter scale can be used to measure
the magnitude (power) of a tremor using an
instrument called a seismometer.
It uses a logarithmic scale. This means that
a size 6 earthquake on the scale is 10
times larger than a size 5 and 100 times
larger than a size 4.

33
Q

What is the Mercalli scale?

A

The Mercalli scale rates an earthquake’s
intensity based on observations of the
damage on a scale of 1 to 12.
- Measures the impacts of earthquakes
- Uses descriptive phrases and people’s
observations about the damage they can see.
- It is measured on a scale between I and XII.

34
Q

What are examples of DIVERGENT plate boundaries?

A

Mid Atlantic Ridge:
North America and Eurasia are moving apart.
South America and Africa are moving apart.

35
Q

What are examples of CONSERVATIVE plate boundaries?

A

Pacific plate and North American plate.
The North American plate is moving slower than the Pacific plate causing stress.

36
Q

What are examples of COLLISION plate boundaries?

A

Indian plate and Eurasian plate

37
Q

What were the responses to the Haiti earthquake?

A

105k buildings were destroyed and 188k were damaged which left 1.5 million people living in tents or without a home, even 4 years after 230k people were living in temporary housing. This caused 316k people to die, 300k+ people injured and 3m people’s health affected.

38
Q

What are examples of CONVERGENT/DESTRUCTIVE plate boundaries?

A

South American plate and the Nazca plate.

39
Q

What caused the Indian Ocean Tsunami?

A

December 26h 2004. The Indo-Australian plate was Subducting below the Eurasian Plate. Pressure had been building at the destructive subduction zone and eventually the stress was released when the continental plate (Eurasian plate) ‘flicked upwards’.

40
Q

What were the impacts of the Indian Ocean Tsunami?

A

Magnitude 9.0 on the Richter Scale, shallow focus of 30km deep – very high energy. Water was lifted upwards by 10metres along the 1200km faultline. Waves spread across the Indian Ocean and reached 12 countries. Waves move at 500mph in deep water. There were no warning systems in the Indian Ocean to detect the Tsunami. The epicentre was only 155 miles away from Indonesia’s Island of Sumatra. The wave reaches northern Sumatra (Indonesia) just 15 minutes after the earthquake.

41
Q

How can prediction, preparation and protection help reduce tectonic hazard?

A

Prediction - meauring changes in size/shape of a volcano and detecting any rising magma pressure. Sulphur dioxide gas is measured. Rock samples can be collected to detect their temperature and origin by robots. Measure the thermal temperatures of the volcanic rock. Seismographs measure earth tremors leading up to a volcano. All of these are early signs of hazards so people are able to be warned and prepare.

Protect - earthquake proof buildings with counter-weights, x or k bracing. Built on hard rock so seismic waves travel slower reducing the shaking. This is so when an earthquake comes the buildings won’t be prone to as much damage.

Prepare - Drop, cover, hold is an earthquake drill practiced in schools and offices. Emergency kits are packed by families. This is so when an earthquake comes they know what to do.

42
Q

What are the three types of volcano?

A

Cinder cones, composite volcanoes (stratovolcanoes), and shield volcanoes.

43
Q

What are cinder cones?

A

Most common type
Produces lava that is typically basaltic in composition with andesite.
Cone shaped

44
Q

What are composite volcanoes?

A

Composed of lava flows, pyroclastic deposits, and mudflow (lahar) deposits, as well as lava domes.
Composite volcanoes are active over long periods (tens to hundreds of thousands of years), and erupt periodically.
Acidic lava, which is very viscous (sticky

45
Q

What are shield volcanoes?

A

Where a volcano produces low viscosity, runny lava, it spreads far from the source and forms a volcano with gentle slopes.
Most shield volcanoes are formed from fluid, basaltic lava flows.

46
Q

What plate boundary do shield volcanoes form at?

A

Divergent plate boundaries

47
Q

What plate boundary do composite volcanoes form at?

A

Convergent plate boundaries.

48
Q

What plate boundary do cinder cones form at?

A

Convergent plate boundaries.

49
Q

Why were the impacts of the Haiti earthquake so bad?

A

Haiti is directly on a conservative fault.
The epicentre was only 15km southwest of Port-au-Prince.
Magnitude 7
Only 8-10kms deep
GDP per person per year = $650 compared to UKs $29,000
Poor quality concrete, lack of consolidation
Weak cement mixed with dirty or salty sand.
No building code in Haiti, no licensing requirements for architects, engineers, or contractors.
Seismic design is not included in the engineering curriculum in Haiti.
Population of 10 million
50% of the population is in poverty (earning less than $1 a day)
70% of the population are unemployed or underemployed
For every one person, Haiti’s government has $450 of debt
Haiti’s debt is $4.5bn