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GEOGRAPHY 1 PHYSICAL > 2 Hazards > Flashcards

2 Hazards Flashcards

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1
Q

There are 3 plate margins, what are they?

A

Destructive / Convergent margin
Constructive / Divergent margin
Conservative / Transform margin

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2
Q

What is a destructive/convergent plate margin?

A

Where plates move towards each other/collide (e.g. Nazca and South American)

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3
Q

What is a constructive/divergent plate margin?

A

Where 2 plates move away from each other (e.g, Eurasian and North American plate)

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4
Q

What is a conservative/transform plate margin?

A

Where 2 plates move past each-other or side-by-side as they move at different speeds (e.g, San Andreas Fault line)

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5
Q

h

A
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6
Q

Earth’s structure:
What does the Earth’s structure consist of?

A

Inner core -> outer core -> mantle (asthenosphere and lithosphere within it, but lithosphere is crust and uppermost part of the mantle) -> crust

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7
Q

Earth’s structure:
Describe the core.

A
  • core in general is the centre of the earth that gives the earth its magnetic field
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8
Q

Earth’s structure:
Describe the inner core

A
  • solid iron-nickel mass
  • 1250 km thick
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9
Q

Earth’s structure:
Describe the outer core

A
  • liquid
  • 2,900 km thick
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10
Q

Earth’s structure:
Describe the mantle

A
  • 80% of the Earth’s volume
  • consists of semi-solid rock also known as molten rock/magma which is silicon and oxygen
    2900km thick
    -
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11
Q

Earth’s structure:
What’s the upper layer of the mantle? What is this?

A
  • Asthenosphere
  • 100km - 300km thick
  • It has plastic properties that allow it to flow under pressure
  • It’s slow-flowing and viscous
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12
Q

Earth’s structure:
Describe the 2 types of crust you can find and their characteristics.
(solid/liquid/gas, composition/made up of…, how deep, cover of earth, age, density)

A

Continental crust
- solid
- made up of dense basalt rock
- 5km deep (average)
- 40% of earth’s surface
- > 1500 years old
- 2.6 g/cm3​ dense

Oceanic crust
- solid
- made up of granite (less dense than basalt)
- 30 km deep (average)
- 60% of earth’s surface
- < 200 million years old
- 3.0 g/cm3​

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13
Q

Earth’s structure:
Where can you find the lithosphere?

A

The lithosphere is the crust and the uppermost part of the mantle.

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14
Q

Earth’s structure:
What are tectonic plates?

A

Tectonic plates are giant slabs of rock that fit together to make up Earth’s lithosphere.

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15
Q

Earth’s structure:
What are tectonic plates made up of?

A

Lithosphere

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16
Q

Earth’s structure:
What do the tectonic plates lie on top of/lie on?

A

Asthenosphere/ the area of molten rock

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17
Q

Earth’s internal energy sources:
What is the core’s temperature and why is it so warm/what has caused it to be so warm? (2)

A

5000C
- Primordial heat because of when the Earth was made
- Radiogenic heat - natural radioactive decay of isotopes such as uranium, thorium and potassium

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18
Q

Earth’s internal energy sources:
What does the Earth’s internal heat source provide?

A
  • Energy for plate tectonics to move
  • Earthquakes
  • Volcanic eruptions
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19
Q

NOTE - Lithosphere and asthenosphere are modern day terms for crust and mantle

A
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20
Q

Plate tectonic theory:
What percentage of the Earth do tectonic plates cover?

A

95%

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21
Q

Plate tectonic theory:
How many major tectonic plates are there in the world? List them.

A

7
- Pacific
- North American
- South American
- Antarctic
- African
- Eurasian
- Indo-Australian

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22
Q

How many smaller tectonic plates do we have?
List them.

A

3 or 4
- Arabian
- Indian
- Nazca
- Caribean plates

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23
Q

Plate tectonic theory:
Describe what plate tectonics are.

A

Rigid rafts of floating rocks on the underlying semi-molten mantle (asthenosphere).

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24
Q

Plate tectonic theory:
Who came up with the plate tectonic theory and when?

A

Alfred Wegener in 1912.

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25
Q

Plate tectonic theory:
What was his theory?

A

A single continent/supercontinent once existed 300 million years ago called the Pangea.

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26
Q

Plate tectonic theory:
What were the next stages after Pangea?

A

A further split in Pangea, which resulted in 2 continents of Laurasia (north) and Gondwanaland (south).
Today, our continents are a further split of Gondwanaland and Laurasia.

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27
Q

Plate tectonic theory:
What would Wegener say about continents today?

A

That the formation of our continents were not always as they are, currently.

28
Q

Plate tectonic theory:
How are continents in the position that they’re in now?

A

Through continental drift.

29
Q

Plate tectonic theory:
What evidence did Wegener use to prove the theory of tectonic plates?

A

Geological and biological.

30
Q

Plate tectonic theory:
What was Wegener’s geological evidence? (3)

A
  • Fit of continents (as previously seen by Francis Bacon in 17th century. Example - South America and West Africa fit like a jig-saw.
  • Glacial deposits were made 290 million years ago that were found in India, Antarctica and South America. If all were made at the same time, then they must have been together at some point.
  • Rock sequences have been found in Scotland and Canada.
31
Q

Plate tectonic theory:
What was Wegener’s biological evidence? (animals and plants) (3)

A
  • Similar fossils (animals and plants) have been found in both India and Australia (therefore, they must have been once connected)
  • Mesosaurus fossils (type of alligator) were found in both South America and South Africa (therefore, they were joined together once)
  • Plant fossils in Antarctica in India (climates must have been very similar at one point and so they must have been close together)
32
Q

Plate tectonic theory:
Before Wegener, who discovered that continents can fit like jigsaws?
Why did no one take him seriously?

A

Francis Bacon
Because he did not have any evidence to prove that they moved.

33
Q

Development of plate tectonic theory:
What was one issue with Wegener theory? Why has there been more development of the theory?

A

He did not explain HOW these tectonic plates moved.

34
Q

Development of plate tectonic theory:
What have scientists discovered as to why tectonic plates move?

A

Sea-floor spreading.

35
Q

Plate tectonics:
What are tectonic plates moved by?

A

Convection currents

36
Q

Plate tectonics:
What makes convection currents move the way they do?

A

The magma heated from the core’s heat of 5000C expands, making it become less dense.

37
Q

Plate tectonics:
If convection currents make tectonic plates move, in what direction can they go?

A
  • Anywhere
  • They can make tectonic plates move towards each other (destructive/convergent)
  • Move away from each other (constructive/divergent)
  • Slip beside each other (conservative)
38
Q

Plate tectonics:
Is plate movement slow or fast?

A

Slow

39
Q

Plate tectonics:
Are earthquakes formed from sudden or slow moving tectonic plates?

A

Sudden

40
Q

Where are most landforms found?
Give examples of landforms.

A

On plate margins

41
Q

Development of plate tectonic theory:
What have scientists discovered as to why tectonic plates move?

A

Sea-floor spreading

42
Q

Development of plate tectonic theory:
What is the reason for continental drift?

A

Sea-floor spreading

43
Q

NOTE -
Convection currents don’t cause tectonic plates to move, they only help them to. Rather, slab pull, (at destructive margins) and ridge push (at constructive margins) cause tectonic plates to move.
This is because convection currents are in the mantle (rise from the heated outer core up to the asthenosphere’s surface) whereas slab pull and ridge push occur on the lithosphere.

A
44
Q

Development of plate tectonic theory:
What main example could you give that show that sea-floor spreading occurs?

A

Mid-Atlantic ridge (MAR)

45
Q

Development of plate tectonic theory:
Where is the MAR situated?

A

Pacific Ocean

46
Q

Development of plate tectonic theory:
How did scientists discover that sea floor spreading occurred?

A

Through examination of the oceanic crust either side of the MAR

47
Q

Development of plate tectonic theory:
Why was sea-floor spreading occurring either side of MAR?

A
48
Q

Development of plate tectonic theory:
At what plate boundary does sea-floor spreading occur at?

A

Constructive/convergent plate boundaries.
Meaning that the 2 plates - North American and Eurasian - move away from each other.

49
Q

Development of plate tectonic theory:
Define sea-floor spreading.

A

The lateral movement of new oceanic crust away from a mid-ocean ridge. This occurs through the upwelling of magma at mid-ocean ridges as 2 plates move away from each other. This results in an outward movement on either side of the ridge.

50
Q

Development of plate tectonic theory:
How does sea-floor spreading occur?

A

Material from the mantle pushing up between the 2 oceanic plates, forming more new material. This pushes the 2 plates to the side, whilst solidifying lava and creating new oceanic crust on either side of the MAR.

51
Q

Development of plate tectonic theory:
What evidence is given to prove that sea-floor spreading is occurring?

A

Alternating polarity of the rocks from the North pole to the South pole, every 400,000 years.

52
Q

Development of plate tectonic theory:
How come there are different strips of material with the crusts either side of the MAR?

A

Because of the magnetic field of the earth changing from North to south pole. As molten material rises and solidifies to form a new crust, the new crust includes iron particles. Essentially, these iron particles are attracted to the magnetic field of the earth. Normal = north. When these new crust are set, the iron particles are set and they cannot move.

53
Q

Development of plate tectonic theory:
What’s the reason for continental drift?

A

Sea-floor spreading

54
Q

Development of plate tectonic theory:
The further away from the MAR, the ….(a)…. will be?

A

Older

55
Q

Development of plate tectonic theory:
Some may think that because of sea-floor spreading, that the Earth is growing, is this true? Why?

A

No - because it’s a closed system.

56
Q

Development of plate tectonic theory:
Why might the Earth not be growing?

A

As well as constructive/divergent margins (plates pull away) we also have destructive plate boundaries (push together) because of subduction zones where plates are subducted into the mantle.
constructive - crust is being made
destructive - crust is being lost/destroyed.

57
Q

Development of plate tectonic theory:
What causes seafloor spreading?

A

Convection currents/thermal currents in the mantle

58
Q

Development of plate tectonic theory:
What causes convection currents?

A
59
Q

Development of plate tectonic theory:
Where do convection currents occur?

A

Asthenosphere

60
Q

Development of plate tectonic theory:
What do convection currents do to plates?

A

Move them into different directions

61
Q

Development of plate tectonic theory:
What causes a destructive plate boundary? (convection currents pov)

A

Slab pull

62
Q

Development of plate tectonic theory:
Describe the slab pull process.

A

The denser, oceanic plate subducts into the mantle under the influence of gravity.
Whilst doing so, it pulls the rest the plate along behind it.

63
Q

Development of plate tectonic theory:
What causes a constructive plate boundary? (convection current pov)

A

Ridge push

64
Q

Development of plate tectonic theory:
Describe ridge push.

A

Magma rises as the plates pull apart.
Magma cools to form new plate material.
As it cools it becomes denser and slides down away from the ridge, causing other plates to move away from each other.

65
Q

Development of plate tectonic theory:
Describe the process of convection currents.

A

The less dense magma rises, cools, then sinks again.
1. Heat from the inner core of the Earth convects through the mantle and into the asthenosphere.
2. (Hot) magma rises as the particles spread out, making the magma less dense. The heat from the inner core causes the spread.
3. Magma becomes cooler at the top as it is further away from the inner core (where the heat comes from). Here, the magma becomes more dense and sinks back down to the bottom.
4. The cooler magma is then reheated and it starts to rise again (repeat).
This is called a convection current.
(As the cooler magma comes down, it can push or pull plates away/together.

66
Q

g

A

x

GEOGRAPHY 1 PHYSICAL (3 decks)

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