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Environmental Geology > EARTH’S STRUCTURE AND PLATE TECTONICS > Flashcards

EARTH’S STRUCTURE AND PLATE TECTONICS Flashcards

1
Q

For rocks to be deformed, they must be acted upon by stress which can be classified into three (3) basic types, what are these basic types and explain

A
  • Compression – pushes on rocks from opposite directions which causes rocks to be shortened parallel to the stress applied
  • Tension- pulls rocks from opposite directions, resulting it to become stretched/lengthened
  • Shear- occurs when rocks are being pushed in an uneven manner, causing the rocks to be skewed such that different sides of a rock body slide or move in opposite directions
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2
Q
  • Rocks near the surface of the earth are ___
A

elastic

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3
Q

all elastic materials have an ____, which is the point in which they no longer behave elastically and deformation becomes permanent.

A

elastic limit

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4
Q
  • Also note that when rocks deform they often slide past one another along a fracture plane, at which point the fracture is called a ____
A

fault

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5
Q

The discontinuity between upper and lower crust

A

conrad discontinuity

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6
Q

The discontinuity between lower crust and upper mantle

A

mohorovicic

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7
Q

The discontinuity between upper and lower mantle

A

repetti

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8
Q

The discontinuity between lower mantle and outer core

A

gutenberg

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9
Q

the discontinuity between outer and inner core

A

Lehmann

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10
Q

describe crusts density and thickness

A

7 to 70 km thick, low density

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11
Q

describe mantles density and thickness

A

high density rocks; 2890 km; and it constitures ~83% of earths total volume

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12
Q

earths radius

A

6371 km

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13
Q

upper mantle depths in km

A

660 km

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14
Q

solid and rigid and is 100km thick

A

lithosphere

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15
Q

mantle contains an average of ~______ SiO2 which means it has an ultrabasic composition

A

~40 to 45%

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16
Q

The uppermost part of the mantle and the crust together constitute the relatively rigid ____, which is strong enough to rupture in response to stress

A

lithosphere

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17
Q

A discrete _______ occurs within the upper mantle at depths of ∼100 – 250km below the surface. The top of these zone marks the contact between the strong lithosphere and the weak asthenosphere

A

Low velocity zone (LVZ)

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18
Q

A discrete _______ occurs within the upper mantle at depths of ∼100 – 250km below the surface. The top of these zone marks the contact between the strong lithosphere and the weak asthenosphere

A

Low velocity zone (LVZ)

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19
Q

The asthenosphere is more _____ and flows slowly, rather than rupturing, when subjected to stress

A

plastic

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20
Q

Mineral transformations within the transition zone

A

Olivine > Wadleysite/Beta Spinel > Ringwoodite/Garnet > Perovskite/Periclase

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21
Q

Major Minerals in the Mesosphere (660km to ~2900km depth)

A
  • Perovskite and Periclase [(Mg, Fe) O]
  • Magnesiowustite [(Mg, Fe) O]
  • Illmenite [(Fe,Mg)TiO2]
  • Stishovite (SiO2)
  • Ferrite [(Ca, Na, Al) Fe2O4]
22
Q

above Core - Mantle boundary, ranges from~130 km to 340 km

A

D” Layer

23
Q

Hutko et al. (2006) detected subducted lithosphere that had ______ all the way to the D″ layer and may be responsible for the anomalously ____

A

sunk; fast velocities

24
Q

Williams and Garnero (1996) proposed an ______in the lowermost mantle on seismic evidence. May be related to the formation of deep mantle plumes within the lower mantle.

A

ultra-low velocity zone (ULVZ)

25
Q

Consists primarily of Fe (~85%) with smaller, but significantly amounts of Ni (~5%) and lighter elements (~8-10%) such as O, S and/or H.

A

Core

26
Q

the _____ core has less O, S and H than in the ____ core

A

inner; outer

27
Q

The outer core is inferred to be a liquid with a density of _____while the inner core has a density of _____.

A

10-12 g/cm3 ; ~13g/cm3

28
Q
  • Seismic studies have shown that the inner core is seismically _____
A

anisotropic

29
Q

Heat sources of the Earth

A

Heat from when the planet formed and accreted
Frictional heating caused by denser material sinking to the center of the planet
Heat from the decay of naturally occurring radioactive elements/nuclides

30
Q
  • an important theoretical and conceptual framework for understanding the origin and global distribution of various rock types
A

Plate Tectonics

31
Q

lithosphere is broken along major fault systems into large pieces called ____

A

plates

32
Q
  • The relative movement of plates with respect to the boundary that separates them defines three major types of plate boundary segments: which are
A

(1) divergent plate boundaries,
(2) convergent plate boundaries,
(3) transform plate boundaries.

33
Q

How did geoscientists discovered the plate tectonics theory?

A

Early evidences and continental drift

34
Q

1922, _____Alfred Wegener published a book outlining the hypothesis of continental drift; suggested that a supercontinent, Pangaea once existed and broke up 200 my ago

A

Alfred Wegener

35
Q

4 evidences of continendtal drift

A

continental fit
fossil evidence
rock type and structural similarities
paleoclimatic evidence

others,
polar wandering
Earthquakes
hot spots
evidence from ocean drilling

36
Q
  • Age of sediment ____ with distance from the ridge
A

increases

37
Q
  • all major interactions (earthquakes, volcanism, orogeny) between plates occur along ______
A

plate boundaries

38
Q

what drives plate tectonics?

A

mantle convection
ridge push
slab pull

39
Q

the Earth’s ____ drives mantle convection, which results into plate motions, plumes, volcanoes, earthquakes, mountain ranges, mineral deposits, etc

A

internal heat

40
Q

3 types of plate boundaries and explain each

A

divergent plate boundary - two plates are moving apart relative to their boundary.
Convergent Plate Boundaries- The process by which the leading edge of a denser lithospheric plate is forced downward
Transform plate boundaries are characterized by horizontal motion, along transform fault systems, which is parallel to the plate boundary segment that separates two plates

41
Q

Horizontal extension in continental lithosphere is marked by _________ and in oceanic lithosphere by the _____.

A

continental rift systems; oceanic ridge system

42
Q

modern examples of continental rift valleys

A

East African Rift
the Rio Grande Rift in the United States
the Dead Sea Rift in the Middle East

43
Q

a new and growing ocean basin begins to form between the two continents by the process of _______

A

sea floor spreading.

44
Q
  • The ____ is Earth’s largest mountain range and covers roughly 20% of Earth’s surface. The ridge is >70,000km long, vary in width from 1000 to >4000km, and rises to a crest with an average elevation of ∼3km above the surrounding sea floor.
A

oceanic ridge system (ridge)

45
Q

warmer, faster-spreading portions of the ridge such as the East Pacific Rise (∼6 – 18cm/yr) have ___ than colder, slower spreading portions such as the Mid -Atlantic Ridge (∼2 – 4cm/yr).

A

gentler slopes

46
Q

process by which the leading edge of a denser lithospheric plate is forced downward into the underlying asthenosphere is called _____

A

subduction.

47
Q

The down going plate is called the _______; the less dense plate is called the ______. The area where this process occurs is a _______.

A

subducted plate or down-going slab;
overriding plate
subduction zone

48
Q

3 types of convergent plate boundaries

A

(1) oceanic-continental convergence; (2) oceanic-oceanic convergence; and (3) continental-continental convergence

49
Q

Transform faults are either classified as ____ or ____

A

left-lateral (sinistral) or right-lateral (dextral).

50
Q

long-lived areas in the mantle where anomalously large volumes of magma are generated.

A

hotspots

51
Q

They occur beneath both oceanic lithosphere and continental lithosphere as well as along divergent plate boundaries. give examples of hotspots that happened in oceanic lithosphere, continental lithosphere and divergent plate boundaries

A

oceanic lithosphere (e.g., Hawaii)
continental lithosphere (e.g., Yellowstone National Park, Wyoming)
divergent plate boundaries (e.g., Iceland).

Environmental Geology (5 decks)

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