EARTH’S STRUCTURE AND PLATE TECTONICS

Question 1

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

Answer 1

• 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

Question 2

• Rocks near the surface of the earth are ___

Answer 2

elastic

Question 3

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

Answer 3

elastic limit

Question 4

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

Answer 4

fault

Question 5

The discontinuity between upper and lower crust

Answer 5

conrad discontinuity

Question 6

The discontinuity between lower crust and upper mantle

Answer 6

mohorovicic

Question 7

The discontinuity between upper and lower mantle

Answer 7

repetti

Question 8

The discontinuity between lower mantle and outer core

Answer 8

gutenberg

Question 9

the discontinuity between outer and inner core

Answer 9

Lehmann

Question 10

describe crusts density and thickness

Answer 10

7 to 70 km thick, low density

Question 11

describe mantles density and thickness

Answer 11

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

Question 12

earths radius

Answer 12

6371 km

Question 13

upper mantle depths in km

Answer 13

660 km

Question 14

solid and rigid and is 100km thick

Answer 14

lithosphere

Question 15

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

Answer 15

~40 to 45%

Question 16

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

Answer 16

lithosphere

Question 17

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

Answer 17

Low velocity zone (LVZ)

Question 18

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

Answer 18

Low velocity zone (LVZ)

Question 19

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

Answer 19

plastic

Question 20

Mineral transformations within the transition zone

Answer 20

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

Question 21

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

Answer 21

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

Question 22

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

Answer 22

D” Layer

Question 23

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

Answer 23

sunk; fast velocities

Question 24

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.

Answer 24

ultra-low velocity zone (ULVZ)

Question 25

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.

Answer 25

Core

Question 26

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

Answer 26

inner; outer

Question 27

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

Answer 27

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

Question 28

- Seismic studies have shown that the inner core is seismically _____

Answer 28

anisotropic

Question 29

Heat sources of the Earth

Answer 29

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

Question 30

- an important theoretical and conceptual framework for understanding the origin and global distribution of various rock types

Answer 30

Plate Tectonics

Question 31

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

Answer 31

plates

Question 32

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

Answer 32

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

Question 33

How did geoscientists discovered the plate tectonics theory?

Answer 33

Early evidences and continental drift

Question 34

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

Answer 34

Alfred Wegener

Question 35

4 evidences of continendtal drift

Answer 35

continental fit fossil evidence rock type and structural similarities paleoclimatic evidence others, polar wandering Earthquakes hot spots evidence from ocean drilling

Question 36

- Age of sediment ____ with distance from the ridge

Answer 36

increases

Question 37

- all major interactions (earthquakes, volcanism, orogeny) between plates occur along ______

Answer 37

plate boundaries

Question 38

what drives plate tectonics?

Answer 38

mantle convection ridge push slab pull

Question 39

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

Answer 39

internal heat

Question 40

3 types of plate boundaries and explain each

Answer 40

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

Question 41

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

Answer 41

continental rift systems; oceanic ridge system

Question 42

modern examples of continental rift valleys

Answer 42

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

Question 43

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

Answer 43

sea floor spreading.

Question 44

- 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.

Answer 44

oceanic ridge system (ridge)

Question 45

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).

Answer 45

gentler slopes

Question 46

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

Answer 46

subduction.

Question 47

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

Answer 47

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

Question 48

3 types of convergent plate boundaries

Answer 48

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

Question 49

Transform faults are either classified as ____ or ____

Answer 49

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

Question 50

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

Answer 50

hotspots

Question 51

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

Answer 51

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