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Geography > Tectonic Processes And Hazards > Flashcards

Tectonic Processes And Hazards Flashcards

1
Q

What is a tectonic hazard?

A

Natural events formed due to tectonic activity (subduction) which has the potential to threaten both life and property

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2
Q

What are the three main tectonic hazards

A

Earthquakes
Volcanoes
Tsunamis

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3
Q

Give two examples of past volcanic eruptions

A

Mt. Vesuvius, Italy 79ad
Nevado del Ruiz, Columbia- 1985
Eyjaffajokull- 2011
Mt Toabora- 1815

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4
Q

Give to examples of past earthquakes

A

Sendai, Japan- March 2012
Sumatra, Indonesia - December 2004

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5
Q

Why is the pacific rim know as the ring of fire?

A

75% of earths volcanoes are located here
90% of earths earthquakes occur here

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6
Q

What are the four types of plate boundary

A

Destructive
Constructive
Collision
Transform

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7
Q

What happens at constructive plate boundary

A

Two oceanic plates move apart or crease new land

Mid-Atlantic ridge
Effusive eruptions and earthquakes

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8
Q

What happens at destructive plate margins

A

A continental and oceanic plate come together the oceanic plate subducts underneath the continental crust
—> —. ____

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9
Q

What happens at transform margins

A

Two plates slide past each other
!|
!|
!|
The San Andreas fault line
Powerful earthquakes

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10
Q

Why does the uk appear to be free from major tectonic hazards

A

It isn’t near any plate boundaries

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11
Q

What is an intro-plate earthquake

A

Earthquakes that occur in the middle of tectonic plates where the pressure of the tectonic plate being squashed and forced to move builds up and is released through cracks in the rocks associated with fault zones resulting in an earthquake

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12
Q

Where is an example of intra-plate earthquakes

A

Mississippi valley

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13
Q

What is the reelfoot rift zone

A

Which is a basin of an old lake which now how loose sediment at its base

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14
Q

Why are ancient fault lines found running through the middle of tectonic plates?

A

750 million yrs ago NA split from supercontinent RODINA leaving faults in central NA

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15
Q

What is a scar zone

A

Zones where fault lines were found in the past

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16
Q

What can cause earthquakes along scar zones?

A
  1. Movement of molten rock below the earths surface causes an intense build up of pressure which is later released along the faults
  2. Activity along existing margins may if strong enough cause reactivation of weakened areas
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17
Q

What is intra-plate volcanism

A

Volcanic activity away from a plate boundary

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18
Q

What is another name from infra-plate volcanism

A

Hotspot

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19
Q

What is a hotspot

A

Is an area on earths surface that exists over a mantle plume

20
Q

What is a mantle plume

A

An area under the rocky outer layer of earth (crust)
Where magma is hotter then surrounding magma
Heat from extra hot magma melts and thins the earth

21
Q

Ate mantle plumes affected by plate movement

A

No- magma plumes remain stationary
This creates a chain of progressively older hotspot volcanoes with only one remaining active.

22
Q

What is an example of a intra-plate island chain

A

South-Pacific island chain

23
Q

What is the formation of a hotspot

A

Thin weakness on crust allows magma escape onto the surface
Ocean water cools the magma over time the land grows to become a submarine volcano
When the volcano breaches the surface it becomes a volcanic island
Move from hotspot becomes a island
Erosion becomes seamount

24
Q

What is the structure of the earth top to centre

A

Crust/lithosphere
Asthenosphere
Mantle
outer core
Inner core

25
Q

What does rheid mean

A

Semi molten

26
Q

How thick/warm is the crust

A

100km
Up to 400*c
Made up of oceanic and continental

27
Q

What are the properties of oceanic crust

A

Basaltic rock
Denser then continental 3G/cm*3
Around 6km thick on average

28
Q

What are the properties of continental crust

A

Made of granitic rock
Density = 2.7g/cm*3
On average around 40km thick

29
Q

What are the properties of the asthenosphere

A

Semi-molten
80 to 200km
Less the 1300c
3.3G/cm3

30
Q

What are the properties of the mantle

A

Liquid material
2900km thick
3.4g/cm3
3700c
Iron, nickel and magnesium

31
Q

Properties of the outer core

A

2200km thick
Liquid iron and nickel
4500-5500c
12.6 and 13g/cm3

32
Q

What are the properties of the inner core

A

2440km thick
5200c
Solid
9.9 and 12.2g/cm3
Iron and nickel

33
Q

What are convection currents

A

Created by the mantle radiating heat outwards from the inner core caused less dense material to rise
Silicate rush metal is under immense pressure and when heated behaves like a viscous liquid

34
Q

What do convection currents do

A

Carry heat from the core to the upper mantle
Plates will move according to the convection currents

35
Q

What is seafloor spreading

A

When the plates split apart
Occurs at mid ocean ridges where new oceanic crust is formed

36
Q

What is ridge push

A

When magma pushes the plates apart
Continuous linked to sea floor spreading
Not accepted don’t think it’s powerful enough as there are no tensional force in the mantle

37
Q

What is slab pull

A

More accepted theory
Gravitational pull of subducted lithosphere is what causes plate movement
The plate sinks at an ocean trench pulling the rest of the plate

38
Q

What are fissure eruptions

A

Key feature of volcanic activity in zones of active rifting on land
Basaltic lava
East African Rift Valley

39
Q

What is the fossil evidence for continental drift

A

1910 Alfred Wegner
Mesosaurus (freshwater) separated by Pacific Ocean
Africa and SA have different climates in present day

40
Q

What are sediment cores used for

A

Taken from ocean floor to date the crust

41
Q

What is paleomagnetism

A

Study of earths past magnetic field in rocks by looking at the formation of iron in the rocks

42
Q

How many times does earths polarity reverse every 1 million years

A

4 times

43
Q

How does rock respond to changes in earths polarity

A

Iron in the molten magma line sup parallel to the magnetic field at the time of eruption

44
Q

Why are the magnetic bands symmetrical (iron bands)

A

As each side of the mid ocean ridge is moving apart at the same speed

45
Q

What the equation for annual rate of spreading

A

Distance moved in cm
——————————-
Number of years taken

46
Q

Where do intraplate earthquakes occur in the US?

A

New Madrid seismic zone central USA

47
Q

How many significant earthquakes were recorded in the new Madrid seismic zone between 1811 and 1812?

A

3 ranging from 7.3 to 7.5

Geography (103 decks)

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