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EOSC 114 > Earthquakes 2 > Flashcards

Earthquakes 2 Flashcards

1
Q

List and describe the three main types of stress

A

All forces are opposite and…

  1. Compression
    - act towards each other
  2. Tension
    - act away from each other
  3. Shear Stress / Transverse
    - act parallel but across a plane
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2
Q

What are the 3 types of plate boundaries?

A
  1. Divergent
  2. Convergent
  3. Transform Boundary
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3
Q

Faults are

A

large brittle fracture in a rock body
- movement range is mm to km

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4
Q

What is the point of origin for many earthquakes?

A

faults

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5
Q

What are faults called based on their movement range?

A

Fractures: mm to cm
Faults: m to km

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6
Q

What are plate/tectonic margins?

A

contact / boundary between plates
- like very large faults but we refer to them as margins

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7
Q

Hanging wall block vs footwall block

A

Hanging: block above the fault
Foot: block below the fault

&laquo_space;Refer to slides for diagram&raquo_space;

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8
Q

Normal Fault

A
  • blocks move AWAY
  • HW moves down relative to FW (and vice versa)
  • caused by tension
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9
Q

Reverse Fault

A
  • blocks move towards
  • HW moves up relative to FW
  • caused by compression
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10
Q

Thrust Fault

A
  • motion similar to reverse fault except low angle + large displacement
  • blocks move towards
  • HW moves up relative to FW
  • caused by compression
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11
Q

The Rocky Mountains are likely made by what type of faults?

A

thrust faults

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12
Q

Strike-Slip Fault

A
  • vertical fault, no FW or HW
  • motion is lateral (like traffic)
  • caused by shear stress
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13
Q

What are the types of strike slip faults? How can we tell?

A

Left lateral and right lateral

&laquo_space;slides for pic&raquo_space;
face the fault, whichever way it moved is the name

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14
Q

The type of stress determines what type of ____ we have

A

boundary

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15
Q

describe continental plates

A
  • felsic / granite
  • light colour
  • relatively thick
  • less dense
  • float high
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16
Q

describe oceanic plates

A
  • mafic / basalt
  • dark colour
  • relatively thin
  • more dense
  • float low
17
Q

what phase is the asthenosphere?

A

solid but deforms plastically + mobile

18
Q

Do plates move independently of each other?

A

oui

19
Q

Divergent plate margins movement + type of stress

A
  • starts with a rift or rift valley in a continent
  • plates move apart
  • tension stress
20
Q

What happens at a divergent margin?

A
  • extensive volcanism begins
  • continental crust thins
  • oceanic crust forms at bottom of rift
  • starts a new ocean basin
  • becomes mid-ocean ridge where new oceanic crust is created and older is pulled away
21
Q

Divergent margins are associated with what hazards?

A

volcanism and many small earthquakes

22
Q

Convergent margins movement

A
  • plates moving together
  • oceanic plates more dense so they will subduct
23
Q

What are the 3 variations of convergent margins?

A
  1. oceanic-oceanic
  2. oceanic-continental
  3. continental-continental (NO subduction)
24
Q

What is subduction

A

when plates are pushed together, the denser oceanic one goes down to mantle

-> older = colder = more dense

25
Q

Convergent margins: What will happen if subduction occurs?

A
  1. extensive volcanism
    - island arcs if ocean-ocean
    - intermediate if continental
  2. mountain building
  3. many earthquakes
    - small to large to very large, megathrust (9.0 +)
    ex/ Tokyo
26
Q

Mountain building occurs at what type of margins?

A

convergent

27
Q

Convergent margins: what will happen if no subduction occurs?

A

(i.e. no oceanic plates involved)

  • mountain building
  • many earthquakes (up to 8+)
  • little to no volcanism
28
Q

Transform Boundaries

A
  • move laterally
  • shear stress
  • like traffic
  • no space problems = no mountains form
29
Q

What happens as a result of transform boundaries?

A
  • little to no volcanism
  • many earthquakes (moderate to large) but NOT as big as convergent margins
30
Q

Do convergent margins have bigger earthquakes or transform boundaries?

A

convergent margins

31
Q

What will happen to plate margins if the stresses change?

A

boundaries may change as well!

  • plate margins react to stress, and all margins are interrelated
32
Q

Can boundaries change?

A

yah

33
Q

Do mountains form on transform boundaries?

A

nah

34
Q

Are divergent margins threatening?

A

generally not

35
Q

Subduction occurs when what type of crust is involved?

A

oceanic only!

36
Q

Subduction occurs when what type of crust is involved?

A

oceanic only!

EOSC 114 (30 decks)

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