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Rocks rock! > Lecture 16 > Flashcards

Lecture 16 Flashcards

1
Q

Geology of Canada 4 types of rocks

A
  1. Cordillera
  2. Interior Platform
  3. Canadian shield (Precambrian)
  4. Appalachian
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2
Q

Orogenesis

A

The process of mountain building
due to convergent plate interactions
is known as orogenesis.

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3
Q

Orogenesis orogeny orogen differences

A

Orogenesis (process)
* Orogeny (time event)
* Orogen (physical result)
* Orogenies start with subduction

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4
Q

How orogeny builds mountains

A

Orogenesis creates igneous, metamorphic, and sedimentary rocks. Regional metamorphic rocks are generated from the intense heat and pressure of compression and burial. Contact metamorphic rocks are created by igneous intrusions. Intrusive and extrusive igneous rocks are generated from subduction processes.

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5
Q

Orogenic history of the Appalachians

A

The Appalachians consist
of a complex mountain
belt formed by three
Phanerozoic orogenic
pulses

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6
Q

What are the three Phanerozoic organic pulses

A

Taconic Orogeny: Ordovician
* Acadian orogeny: Late Devonian-Early Carboniferous
* Alleghanian orogeny: Late Carboniferous – Late Permian

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7
Q

What do orogenies start with

A

Subduction

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8
Q

Grenville orogeny

A

1100 Ma

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9
Q

Post greenville riffting

A

600 Ma

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10
Q

Paleozoic passive margin

A

500 ma

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11
Q

Acadian orogeny

A

Acadian orogeny 390-340
Ma (Devonian-Early
Carboniferous

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12
Q

Alleghanian orogeny

A

Alleghanian orogeny (320-260 Ma)
Pennsylvanian-Permian

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13
Q

Orogenic history of the Appalachians

A

East-dipping subduction continued to close the ocean during the late Paleozoic.
Alleghanian orogeny (260 Ma): Africa collided with North America, creating a huge
fold-thrust belt and mountain range; assembled the supercontinent of Pangea.

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14
Q

Break up of Pangea

A

Pangea began to rift apart about 180 Ma. Faulting and stretching thinned the lithosphere.
This led to rifting, the eventual development of seafloor spreading, and the creation of
the Atlantic Ocean

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15
Q

The principal stresses and type of deformation

A

Sigma 1 maximum principal stess (generates compression splits rocks into rifts - makes fold structures)
sigma 2
Sigma 3 minimum

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16
Q

Folding and thrusting

A

Beds that were once horizontal and of equal thickness are now distorted
Asymmetrical structures

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17
Q

Thrust faults

A

Thrust faults act to shorten and thicken mountain belts.
they can transport sheets of rocks hundreds of km

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18
Q

What is a thrust fault

A

Dip slip fault were hanging wall moves up relative to footwall
type of reverse fault where the angle is less than 30 degrees

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19
Q

Folds: Anticline and syncline

A

Anticlines: layer on oposit side of hinge ( imaginary line where it folds)
Dipping in opposite directions
Syncline if they dip in same direction

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20
Q

Plunging folds

A

A plunging fold has a hinge that is tilted.

21
Q

Metamorphism

A

Orogeny is the main cause of metamorphism
Index minerals indicate
the metamorphic grade
of a rock

22
Q
A

The appellation mountains are formed by plate conversion and subduction

23
Q

Metamorphic
facies

A

A metamorphic facies is a
set of mineral assemblages
that indicate a certain range
of P and T conditions
- memorize the graph

24
Q

Plate tectonics and metamorphic facies

A

Memorize graph

25
Q

Shear

A
  • Shear develops when surfaces slide past one another.
  • Shear stress neither thickens nor thins the crust.
26
Q

How to determine sigmas

A

Sigma 1- strongest most obvious
sigma 2- Perpendicular
sigma 3 -

27
Q

Appelatian moutains exsist

A

Appellation belt
subduction during the palezoic

28
Q

Appalachians: site of a former plate boundary

A

Evidence:
- Slivers of oceanic crust
* Slivers of oceanic sedimentary
rocks
* Thrust faults
* Folds
* Crustal thickening

29
Q

Alfred Wegener

A

Alfred Wegener (1880-1930)
postulated that all landmasses were
originally united into a
supercontinent named Pangaea at
the end of the Paleozoic

30
Q

Pangea began splitting 180 million years ago
Indicated by oceanic crust

A
31
Q

India and Asia collision

A

Continent-continent plate boundaries
* Collisions and suturing
During its long journey north, India moved 15 to 20 cm per year; however, beginning 40 to 50 million years ago, its rate of movement decreased markedly as it collided with the Eurasian plate

32
Q

mount everist

A

Collision between india and assia

33
Q

Tien Shan Mountains, China,

A

strike-slip faults
(left lateral)

34
Q

What type of fault is shown

A

reverse fault
because foot wall moved up

35
Q

A dip slip fault where hangaing wall moves up relative to foot wall is called a…

A

thrust fault

36
Q

Hanging wall moves down relative to foot wall

A

Normal fault

37
Q

When did the acadian orogeny end

A

early carboniferous

38
Q

When did Taconic orogeny terminate

A

Late ordovician

39
Q

When did alleghanian orogeny stop

A

permian

40
Q

Devonian sandstone layer structurally rests on a jurassic limestone layer what would be the contact between these layers

A

thrust fault

41
Q

If a cambrian sandstone layer rests ona folded jurestic greenschist rock what would the contact be?

A

thrust fault

42
Q

How many mesozoic orogenic events are recorded in the Appalachian mountains

A
43
Q

the n American continent collided with….. at the end of Permian

A

Africa

44
Q

The n american the taconic orogeny was produced by the…

A

grenvillian orogeny

45
Q

Formation of pagea was produced by the ….. orogeny

A

Alleghanian

46
Q

when did pangea begin to break

A

Jurassic (late)

47
Q

Amphibolte facies rocks represent higher grade metamorphic conditions than greenschists facies rocks

A

True

48
Q

Granulite facies rocks record higher grade metamorphic condition

A

true

49
Q
A

Rocks rock! (6 decks)

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