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Physical geography > tectonic processes and hazards > Flashcards

tectonic processes and hazards Flashcards

1
Q

what are volcanoes?

A

openings in the earth’s crust where gas, lava and ash erupt. Tectonic plates cause pressure to build up and magma and gases rise up reaching the surface

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2
Q

why do volcanoes get bigger over time?

A

lava cools - forms rock - so as the volcano continues to erupt over time it gets bigger, as the rock builds up

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3
Q

lava flows

A
  • very hot (1000 degrees Celsius)
  • move slowly (can be outrun)
  • destroy everything in their path
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4
Q

pyroclastic flows

A
  • hot rock, lava and ash

- move at a very fast speed (cannot be outrun)

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5
Q

tephra and ash falls

A
  • volcanic rock and ash that erupt
  • cause injury and death
  • poor visibility
  • slippery roads
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6
Q

gas eruptions

A
  • magma contains dissolved gases that release into the atmosphere
  • they can travel thousands of miles
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7
Q

lahars

A
  • masses of rock, mud and water travel down sides of volcano
  • caused when eruption melts snow or ice
  • too fast to outrun - deadly
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8
Q

what are hotspots?

A
  • volcanoes that occur in the middle of plate margins

- plumes of hot magma rise up and erupt

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9
Q

how is a chain of volcanic islands formed?

A
  • as the plates move over the hotspot, the volcano is carried away with it and a new one forms
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10
Q

measuring the size and magnitude of volcanoes?

A

The explosivity index

  • height and amount
  • duration of eruption
  • qualitative terms
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11
Q

predicting eruptions

A
  • scientists can detect rock that breaks due to magma using seismograms
  • surface changes shape
  • changes to the tilt of the volcano
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12
Q

what is an earthquake?

A

An earthquake is the result of a sudden release of stored energy in the Earth’s crust that creates seismic waves.

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13
Q

hypocentre / focus

A

the point inside the crust from which the pressure is released

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14
Q

epicentre

A

the point on the surface directly above the focus

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15
Q

What is mantle convection?

A

Heat produced by the decay of radioactive elements in the Earth‘s core, heats the lower mantle creating convection currents

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16
Q

What is slab pull?

A

Newly formed oceanic crust at mid ocean ridges becomes denser and thicker as it cools. It then sinks into the mantle

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17
Q

Subduction?

A

One plate (oceanic) sub ducts underneath the other, and sinks into the mantle.

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18
Q

Sea floor spreading

A

When magma is forced up from the mantle in mid ocean ridges, new oceanic crust is created. This new crust pushes plates apart

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19
Q

Describe the features of

  • inner core
  • outer core
A

Inner - hottest part (mostly solid) 6000•c Iron

Outer - semi molten (iron and nickel) 4500-6000•

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20
Q

What is the mantle?

A

The widest layer.
Surrounds the core of the earth
Between outer layer and crust

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21
Q

What is the difference between oceanic crust and continental crust?

A

Oceanic - more dense but thinner and lines the ocean floors

Continental - older and thicker
Makes up the lithosphere
Covers all continents

22
Q

Oceanic + continental (destructive)

A
  • Oceanic plate is subducted
  • fold mountains created as a result of the collision
  • earthquakes caused by friction
  • volcanoes formed because of melting of the oceanic crust in the mantle
23
Q

Oceanic + oceanic (destructive)

A

The denser oceanic plate is subducted

  • rise up to form separate island volcanoes
  • shallow deep focus earthquakes formed here and are very powerful
24
Q

Continental + continental

A

AKA COLLISION MARGIN

  • sediments crumple up to form high fold mountains
  • compression can cause shallow focus earthquakes which are extremely powerful
25
Q

What are mid ocean ridges and how are they created?

A

Underwater mountain ranges across the ocean floor. They are created from rising magma that erupts onto the sea floor creating new land

26
Q

What are rift valleys?

A

When the plates move apart, the crust stretches and breaks into a set of parallel cracks (FAULT) the land then collapses

27
Q

Conservative plate margins

A

Plates sliding past each other.
Include transform faults
Powerful earthquakes as major pressure can build up from plates that get stuck
(Eg San Andreas fault)

28
Q

Natural hazard?

A

Naturally occurring process that has the potential to affect people

29
Q

Natural disaster

A

Major natural hazard that causes significant social, environmental and economic damage

30
Q

Vulnerability

A

The ability to anticipate cope with, resist, and recover from a natural hazard

31
Q

What does a seismometer do?

A

Detects ground movement

32
Q

Moment magnitude scale factors?

A
  • size of seismic waves
  • rock movement
  • area of fault broken by EQ
  • resistance of rocks affected
33
Q

What does it mean by a logarithmic scale?

A

Each number is 10 times the magnitude of the last number

34
Q

What does the term magnitude mean?

A

The amount of energy released at the epicentre

35
Q

What does the Mercalli intensity scale include

A

Observations from people who experience the earthquake.

Rated on a scale from 1 to X

36
Q

Ground shaking effects

A

Causes infrastructure to collapse resulting in injury and death

37
Q

Crustal Fracturing

A

The earths crust cracks leaving gaps

38
Q

What is liquefaction?

A

Violent shaking can cause rocks to the strength and become more liquid than solid. Therefore buildings can lose their foundation and collapse

39
Q

What is an intraplate earthquake?

A

They occur in the middle of plate margins far from the Boundary

40
Q

What is the tsunami?

A

A Sunami is a series of larger than normal waves, which are usually caused by volcanic eruptions or underwater earthquakes

41
Q

Define the term water column

A

The area of seawater from the surface to seafloor

42
Q

Impacts of tsunami

A
  • sweeping away buildings + people
  • wash away soil destroying everything
  • change the landscape
43
Q

Why can’t we predict Tsunamis

A

Because we can’t predict earthquakes therefore we can only send out warnings

44
Q

What are early warning systems?

A

Use Seismic sensors to detect undersea earthquakes

45
Q

What does the DART system monitor?

A

It monitors changes in sealevel pressure. When Sunami waves are detected, the system sends the information through a satellite for warning systems

46
Q

Benioff zone

A

This is where major friction is created due to the colliding of plates, often resulting in earthquakes

47
Q

p waves

A

primary/pressure waves

  • fastest
  • travel through solids and liquids
  • shake in a back and forwards motion
48
Q

S waves

A

secondary waves

  • slower
  • only travel through solids
  • move sideways at right angle to direction
  • more damaging than p waves
49
Q

L waves

A

Love waves

  • slowest
  • most damaging
  • shake from side to side
  • focus all energy on earths surface
50
Q

how can a countries governance increase its vulnerability?

A
  • building codes are often skipped
  • quality of infrastructure
  • efficiency of emergency services
  • level of corruption
  • how educated communities are on response
51
Q

How can economic and social conditions increase its vulnerability?

A
  • more wealthy = able to afford protection
  • poor quality housing cannot withstand hazards
  • poor health care can cause disease outbreaks
52
Q

how can physical and environmental conditions increase vulnerability?

A
  • high population density - more people at risk
  • rapid urbanisation - poor quality housing as it has been rushed due to high demand
  • if the accessibility of an area is difficult, it may delay emergency services

Physical geography (5 decks)

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