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A2 Geography - Earth Hazards > Earthquakes > Flashcards

Flashcards in Earthquakes Deck (16)
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1
Q

Divergent Boundary

(Constructive Boundary/ Spreading Ridge)

e.g. Iceland

A

= a plate boundary at which new material is being created

2
Q

Convergent Boundary

(Destructive Boundary)

e.g. off the west coast of South America

A

= a plate boundary at which material is destroyed at a subduction zone

Explanation = where oceanic crust and continental crust converge, the denser oceanic crust plunges under the lighter, less dense continental crust into the mantle. This is a subduction zone.

Results=

  1. island arc - when this happens under the sea instead of under the continent
  2. mountains - crumpling of sediment as the plates push together
3
Q

Collision Boundary

e.g where Eurasian and Indian plate collide to form the Himalayas

A

= a plate boundary in which two similar plates come together - neither is destroyed, but both are folded to form fold mountains

4
Q

Conservative Boundary

(Transform Boundary)

e.g the Sand Andreas fault where the North American plate and Pacific plate move in the same direction but at different speeds.

A

= a plate boundary in which two similar plates move past each other - neither is destroyed but earthquake activity is common

5
Q

What are the 3 geographical issues associated with earthquakes?

A
  1. impact on human activities
  2. human activities increasing the impacts of earthquakes
  3. physical factors increasing the impacts of earthquakes
6
Q

What is the epicentre?

A

the point on the earth’s surface vertically above the focus of an earthquake

7
Q

What is the hypocentre (aka the focus)

A

the point inside the crust where the earthquake energy is released in seismic waves

8
Q

What does an S wave do?

A

shake the ground perpendicular to the direction of travel

9
Q

What does a P wave do?

A

shakes the ground parallel to the direction of travel

10
Q

What are the 2 main types of seismic waves?

A
  1. body waves (s waves and p waves)

2. surface waves (love waves and raleigh waves)

11
Q

Whats the difference between body waves and surface waves?

A
  1. location
    surface waves = restricted to and guided by surface
    WHEREAS
    body waves = can travel through the whole earth
  2. place of origin
    surface waves = epicentre
    body waves = focus/ hypocenter
12
Q

What does a love wave do?

A

create a rolling motion

13
Q

What does a raleigh wave do?

A

shake the ground at right angles to the direction of movement

14
Q

what type of seismic waves cause most of the damage near the epicentre?

A
  • surface waves (love waves and raleigh waves)
15
Q

What is an earthquake?

A

a sudden violent shaking of the ground, typically causing great destruction, as a result of movements within the lithosphere or volcanic action

16
Q

What causes an earthquake

A
  • when tectonic plates move alongside each other friction occurs, causing a build up of stress and a deformation of rock
  • this stress is stored as elastic energy
  • when this stress exceeds the strength of the fault, the rock fractures and rebound to their original positions
  • when this happens, seismic waves are released