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EESC 111 > Chapter 2 Plate Tectonics > Flashcards

Chapter 2 Plate Tectonics Flashcards

1
Q

What was Alfred Wegener’s first piece of evidence for Continental Drift Hypothesis?

A

The similarities in the coastlines of South America and Africa.

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2
Q

Why are fossils important to the hypothesis of Continental drift?

A

Similar rocks, fossils, and glacial formations were formed on continents that do not currently have conditions for these geological features. Ex: Glacial till in Australia

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3
Q

What important piece was Alfred Wegener missing to help prove the theory for continental drift?

A

A mechanism for how the continents moved. (convection in the mantle is the major force of plate movements, along with gravity and density)

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4
Q

Which scientist proposed the theory of seafloor spreading?

A

Harry Hess

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5
Q

What is the theory of seafloor spreading?

A

Mid-ocean ridges (divergent plates) spread and force new material to the surface, while creating new seafloor.

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6
Q

What is Paleomagnetism?

A

When in liquid state, minerals align themselves with Earth’s magnetic field. When the rock cools, the alignment is frozen in place. Kind of like a fossilized compass

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7
Q

In which layer of the earth do most earthquakes occur?

A

The crust

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8
Q

Is continental crust more dense or Oceanic crust?

A

Oceanic crust (think, subduction along continental boundaries)

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9
Q

Which layer of Earth is the largest chemical layer by volume?

A

The mantle, to a depth of 2900 km.

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10
Q

What does the inner core mainly consist of

A

A very dense iron core.

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11
Q

What are the five physical layers?

A

Lithosphere, Asthenosphere, Mesosphere, Outer and Inner core

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12
Q

The Lithosphere is the outermost physical layer of Earth. What two types of lithosphere are there?

A

Continental and Oceanic Lithosphere

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13
Q

Which layer drives the movement for tectonic plates?

A

The Asthenosphere. (Astheno means lacking strength)

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14
Q

What is the mesosphere?

A

Called the lower mantle. More rigid and immobile than asthenosphere. Located 410 to 660 km below Earth’s surface. Minerals continuously change into various forms in this zone.

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15
Q

What physical layer is the only entirely liquid layer?

A

The Outer Core.

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16
Q

What keeps the inner core solid?

A

The immense pressure keeps the minerals of the inner core in a solid phase.

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17
Q

What generates the earth’s magnetic field?

A

The circulation of molten iron and nickel within the Outer Core.

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18
Q

True or false: North and South America’s eastern coastlines are examples of active margins

A

False (passive margin)

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19
Q

Convergent boundaries move _____

A

Toward each other (destructive boundaries)

20
Q

What two types of convergent boundaries are there?

A

Subduction and collision, depending on density

21
Q

Where does subduction most often occur?

A

Between Oceanic plates and Continental plates

22
Q

As an oceanic plate descends, it pulls the ocean floor down into a trench. What is the average yearly rate of oceanic plate subduction?

A

Half an inch per year

23
Q

When ocean floor sediments are scraped together and compressed between subducting plates and overriding plates, what is this called?

A

The accretionary wedge.

24
Q

When land mass is added to continental plates from ocean floor subduction, what is this called?

A

Terrane

25
Q

When the subducting oceanic plate sinks deep into the mantle…. ___________

A

The immense heat and pressure push material under the continental plate, forming liquid magma which is forced up as volcanism. (See Cascade Range)

26
Q

Which type of plate boundary is known for having the largest earthquakes?

A

Convergent boundaries (Subduction zones)

27
Q

What is the result of Oceanic-Oceanic subduction?

A

Volcanism, and can result in island arcs

28
Q

What occurs when continental plates converge?

A

The plates do not subduct, and instead, collision occurs. Often characterized by tall, non-volcanic mountains. (See: Alps)

29
Q

Constructive boundaries

A

Divergent

30
Q

What are the two types of Divergent boundaries?

A

Continental rift zones and mid-ocean ridges.

31
Q

What two factors determine if continental rifting occurs?

A

A) Does not occur in continents with older and stable interiors, known as Cratons
And B) When rifting occurs, the breaking pattern resembles truncated icosahedron (seams on a soccer ball)

32
Q

What two types of rifts are there?

A

Narrow and broad

33
Q

What is an example of active narrow rifting?

A

The East African Rift Zone

34
Q

What are the characteristics of Mafic rocks?

A

Darker in color and contain more minerals that are dark in color.

35
Q

As oceanic lithosphere continues to diverge, a _________ - ___________ ridge is formed

A

Mid-ocean

36
Q

What is created at mid-ocean ridges?

A

New lithosphere

37
Q

Ridge formation suggests that sections of lithosphere furthest away from mid-ocean ridges will be the oldest. How do scientists test this theory?

A

Comparing the age of rocks from various locations on the ocean floor. Sediment closest to the mid-ocean ridges will be very thin as well.

38
Q

What is the cause of magnetic anomalies along mid-ocean ridges?

A

As magma is released, Earth’s magnetic field is imprinted into the magma. As the spreading continues, these magnetic fields change the further you get from the ridge.

39
Q

Mid-ocean ridges are often studded with _____________________

A

Hydrothermal vents

40
Q

What is a transform boundary often called?

A

Strike slip or conservative boundary

41
Q

A boundary where lithospheric plates slide past each other in a horizontal plane

A

Transform boundary

42
Q

The San Andreas fault is an example of what type of boundary?

A

Transform boundary

43
Q

When transform boundaries are unable to shear past each other, pressure builds up resulting in…

A

Earthquakes

44
Q

_____________ occurs where there is a component of compression in addition to shearing

A

Transpression

45
Q

When a geological feature is cut by a fault it is called…

A

A piercing point.

46
Q

A _________ is an area in the lithospheric plate where molten magma breaks through and creates a volcanic center

A

Hotspot

47
Q

The only type of volcanism NOT associated with subduction zones

A

Hotspots

EESC 111 (4 decks)

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