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Physical Geography > Tectonics, Earthquakes, and Volcanism > Flashcards

Tectonics, Earthquakes, and Volcanism Flashcards

1
Q

How did earths continental crust come to form?

A

Tectonic activity (powered by internal energy ; endogenic) + Weathering and erosion (powered by the Sun through motion of air, water, and ice; exogenic).

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2
Q

What is Crustal Formation?

A

upwelling of magma from diverging plates results in a new oceanic crust, with a new igneous rock, which is mafic (denser). When oceanic plate and continental plate meet, subduction occurs, intrusive or extrusive igneous rock may present themselves.

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3
Q

What are Three Uplifted Crustal Regions?

A
  1. Residual mountains and stable continental cratons
  2. Tectonic mountains and landforms (active)
  3. Volcanic features
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4
Q

How are Residual mountains and stable continental cratons formed?

A

formed from inactive remnants of ancient tectonic activity. Kind of in the middle of plates. (old mountains)

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5
Q

How are Tectonic mountains and landforms formed?

A

produced by active folding, faulting, and crustal movement (young mountains)

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6
Q

How are Volcanos formed?

A

formed by surface accumulation of molten rock from eruptions of subsurface materials.

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7
Q

What is a Craton?

A

A craton, or heartland region, is an old and stable part of the continental crust. Nowhere near the plate boundary.

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8
Q

What are the three forms of Craton?

A

-Continental Shield
-A Platform
-Basement or Crystalline Basement

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9
Q

What is a continental shield?

A

A continental shield is a region with a craton that is exposed at the surface, older stuff.

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10
Q

What is a platform?

A

A platform is a continental area covered by relatively flat or gently tilted sedimentary strata.

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11
Q

What is a basement or crystalline basement?

A

A basement or crystalline basement is a region below a sedimentary platform or cover.

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12
Q

Which layer of craton has the oldest stuff?

A

Sheilds

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13
Q

What is the process of building a continental crust?

A

Includes subduction and remelting (volcanism), plate collisions, accretion. Meeting of plate tectonics, continental plate and an oceanic plate. Oceanic plate gets subducted, we get destruction of that plate, melting upwelling of magma, which creates new intrusive igneous rock or extrusive igneous rock if it reaches the surface.

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14
Q

How are mountains formed?

A

we have continental crust plate collisions, similar densities so either place is going to be resistant to subducting. It was a very energetic collision, resulting in a lot of uplifting.

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15
Q

What is the role of accretion in building continental crust?

A

oceanic plate and continental plate, oceanic plate is being subducted. We get destruction and remelting, on this oceanic plate we have an inactive volcanic island arc riding atop the oceanic plate. That inactive arc will collide with the continental plate, the volcanic island arc becomes part of the continental plate

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16
Q

True or False: Rocks are subjected to stress due to tectonic forces, gravity, and the pressure from overlying rocks.

A

True.

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17
Q

What are the three types of stress on rocks?

A

Tension
Compression
Shear

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18
Q

What does tension stress do?

A

Tension stress causes stretching strain.

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19
Q

What does compression stress do?

A

Compression stress causes shortening strain.

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20
Q

What does Shear stress do?

A

Shear stress causes twisting laterally strain (scissors).

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21
Q

What is a strain on rocks?

A

Strain is how rocks respond to stress and are expressed in rocks by folding (bending) or faulting (breaking).

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22
Q

How is strain expressed on rocks?

A

Folding or Faulting

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23
Q

When rock strata that are layered __________ are subjected to compressional forces, they become deformed.

A

horizontally

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24
Q

When does folding occur?

A

Folding occurs when rocks are deformed as a result of compressional stress and shortening.

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25
Q

What is an Anticline?

A

An arch-shaped upward fold.
- the rock strata slope downward away from an imaginary center axis that divides the fold into two parts

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26
Q

What is a Syncline?

A

A trough-shaped downward fold
-the strata slope upward away from the center axis, slopes downward (Opposite of anticline).

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27
Q

How is synclinal ridge formed?

A

The erosion of a syncline may form a synclinal ridge

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28
Q

When does faulting occur?

A

Faulting occurs when rocks on either side of the fracture shift relative to the other side

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29
Q

What is a fault zone?

A

Fault zones are areas where fractures in the rock demonstrate crustal movement

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30
Q

What is the The fracture surface along which the two sides of a fault move called?

A

Fault Plane

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31
Q

How do you differentiate the three main types of faults?

A

Tilt and orientation of the fault plane

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32
Q

what are the three main types of faults?

A

Normal
Reverse
Strike-Slip

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33
Q

What is a Normal fault linked to?

A

Tensional Stress

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34
Q

What is a Reverse Fault linked to?

A

Compressional Stress

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35
Q

What is a Strike-Slip fault linked to?

A

Lateral-shearing stress

36
Q

Explain the footwall and hanging wall:

A

footwall and hanging wall, footwall is higher during normal faulting. Whereas, during reverse faulting the hanging wall is high.

37
Q

How are fault types classified?

A

Direction of relative displacement

38
Q

_________: is a fault in which the sides of the fault are displaced horizontally.

A

Strike-Slip Fault

39
Q

A fault with vertical displacement is called _____________.

A

Dip-Slip Fault

40
Q

What are the two subcategories of Strike-Slip Faults?

A

Right-Lateral Strike-Slip Fault
Left-Lateral Strike-Slip fault

41
Q

true or false:If the hanging-wall moves up relative to the footwall, it is a reverse (dip-slip) fault. If the hanging-wall moves down relative to the footwall, the fault is called a normal (dip-slip) fault.

A

True.

42
Q

What is Orogenesis?

A

Mountain building

43
Q

what are some types of Orogenesis?

A

Plate Plate Collisions
Capture of Terranes (accretion)
Intrusion of Plutons

44
Q

What happens in the Intrusion of Plutons?

A

intrusion of molten rock (magma), cools and solidifies as intrusive igneous rock, force being pushed outwards, we get uplift (dome formations).

45
Q

Is erosion an endogenic or exogenic process?

A

Exogenic

46
Q

How does mountain building occur?

A

Thickening of Crust Compression Stress Accretion Volcanic Activity (introduction of new rock).

47
Q

What happens when an oceanic plate meets a continental plate?

A

oceanic plate being subducted under continental plate, there is some compression stress occur (folding, building up of land and uplift).

48
Q

How does an earthquake occur?

A

There is immense friction and a buildup of energy or force. Friction is then overcome in a sudden snap or fracture, resulting in a sudden release of this built-up energy and rapid crustal movement (two plates locking up, we will get snaps and breaks result in sudden release of energy, rapid crustal movement (earthquakes).

49
Q

~how many earthquakes happen per year?

A

1 million

50
Q

What are the four phases of an earthquake?

A

focus
epicenter
aftershock
foreshock

51
Q

________________: of an earthquake is the subsurface area along a fault plane, where the motion of seismic waves is initiated

A

Focus

52
Q

_______: the area at the surface directly above the focus.

A

Epicenter

53
Q

___________: series of aftershocks may occur after the main shock (Same general epicenter)

A

Aftershock

54
Q

_______: before the main shock.

A

Foreshock

55
Q

What are the two methods to rate an earthquakes magnitude?

A

Richters Scale
Moment Magnitude

56
Q

What is the Richters Scale?

A

Richter’s scale is based on amplitude of seismic waves, which is related to energy released.

57
Q

What is the Moment Magnitude scale?

A

Moment magnitude scale is based on the amount of fault slippage produced (how much movement we actually had), the size of surface area that ruptured, and the nature of the materials that faulted, which is more accurate than Richter’s scale.

58
Q

how are earthquakes forecasted?

A

Paleoseismology (principle of uniformitarianism). The past is the key to the future. Build hazard maps based on past seismic activity.

59
Q

What is a Seismic Gap?

A

-Areas are overdue for an earthquake (accumulated strain),
-Observe or measure phenomena that might precede an earthquake. Rocks bend, tilt, and swell under accumulated strain.

60
Q

How often to megathrust earthquakes occur?

A

500 years

61
Q

Why do we have a low chance of earthquakes in MB?

A

we have a low chance of earthquakes in Manitoba because there is very little movement of plates by us, we have the shields, which are stable and consistent landscapes.

62
Q

When/what was the first successful earthquake prediction?

A

Chinese scientists made the first successful prediction of a major earthquake in 1975 based on the foreshocks: M7.5 Haicheng earthquake.

63
Q

Define a Volcano:

A

A structure in the earth’s crust containing an opening at the end of a central vent or pipe, through which magma rises from the asthenosphere and upper mantle.

64
Q

Where does magma sit, pre eruption?

A

Magma collects in a magma chamber deep below the surface, until conditions are right for an eruption.

65
Q

How many active volcanos are there?

A

(<600) of these are considered active

66
Q

What are volcanoes associated with?

A

Plate tectonics

67
Q

What are three settings that lead to volcanic activity?

A

Rifting
Hotspots
Subduction

68
Q

Define Rifting in terms of volcanic activity:

A

we can get volcanic activity where we have a rifting either on a mid-ocean rift, where we have divergent plate boundaries, where we have two oceanic plates, in this case, diverging. This rift allows magma to up well from the asthenosphere in the upper mantle to reach the surface.

69
Q

Where do we find hotspots?

A

In the asthenosphere

70
Q

What happens during subduction?

A

The upwelling of magma

71
Q

What are three types of volcanos?

A

Cinder Cone
Shield Volcano
Compositie/Strata Volcano

72
Q

Define a Cinder Cone volcano:

A

Small; cone shaped hill <450m relief

73
Q

Define a Shield Volcano:

A

Large, gently sloping. Mount Aloa

74
Q

Define a Composite Volcano:

A

Formed by multiple layers of lava, ash, and pyroclastic. Tend to have steep sides and a conical shape. Composed of several layers of something.

75
Q

What type of volcano has layers of ash, lava, and pyroclastic?

A

Composite

76
Q

How are volcanic materials classified?

A

composition and how erupted

77
Q

What is lava classified?

A

Mafic (more liquid, intense flow)
Felsic (vicious, and resistant to flow)

78
Q

What are the two textures of cooled lava?

A

Pahoehoe (smooth)
A’a (sharp, jagged)

79
Q

Can gases erupt from a volcano?

A

Yes

80
Q

What is a Pyroclast?

A

pulverized rock and clastic materials of various sizes

81
Q

What are Basaltic Products?

A

Cinders (scoria) bombs, ejected in a violent matter.

82
Q

What is a cinder cone?

A

Small volcanic hill formed from cinders that accumulate during moderately explosive eruptions. Ejection of cinders which pile up and mound to form a Cinder Cone.

83
Q

What controls the profile of a volcano?

A

Viscosity of magma

84
Q

What are some characteristics of an effusive eruption of a shield volcano?

A

Low viscosity, non-violent eruption. Mafic type fluid lava flows along the surface, which results in a gentle slope.

85
Q

What are some characteristics of an effusive eruption of a flood basalts?

A

Effusive eruptions can be massive and long-lasting leading to flood basalts.

86
Q

What are some characteristics of an explosive eruption?

A

cone shape, composite volcanoes, felsic type lava. Builds up pressure and explodes violently.

87
Q

What are some impacts of volcanism?

A

-Ash cloud,
-(CO2) emissions.
-Loss of life / displacement of people

Physical Geography (15 decks)

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