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Geology > Plate Tectonics > Flashcards

Plate Tectonics Flashcards

1
Q

Who was Alfred Wegener? What was his hypothesis?

A

A German meteorologist. Hypothesized that the continents used to fit together as a single
supercontinent he named Pangaea.

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2
Q

Where are earthquakes often found?

A

mid-ocean ridges, transform faults, and deep-sea trenches.

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3
Q

Name 3 pieces of evidence to support the existence of Pangea…

A
  1. Glacial Deposits
  2. Similar species/organisms
  3. Mountain Belts
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4
Q

Is the inner core liquid or solid? outer core?

A

Inner core: Solid

Outer core: Liquid

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5
Q

Hot magma - has no magnetic orientation

A

Cool magma (as it turns solid) - magnetic signature becomes frozen in the rock

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6
Q

What is Sonar?

A

Allows a ship to easily measure sea-floor bathymetry.

Based on the travel time of sound waves generated by the ship and reflected off the bottom.

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7
Q

What was Harry Hess’ hypothesis?

A

Compiled the evidence that new sea floor is created at mid-ocean ridges, moves away from the ridges, and then subducts back into the mantle.

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8
Q

What is Normal Polarity and Reversed Polarity?

A

Normal Polarity - how magnetic dipoles are today

Reversed Polarity - North end of a compass would point south

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9
Q

When does a positive anomaly form?

A

When the polarity of the sea floor is the same direction of the polarity of the Earth.

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10
Q

When does a negative anomaly form?

A

When the polarity of the sea floor is the opposite direction of the polarity of the Earth.

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11
Q

Are positive anomalies strong or weak?

A

Positive anomalies = strong

Negative anomalies = weak

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12
Q

How are magnetic anomaly stripes created?

A

As the mid-ocean ridge adds new basalt to the spreading oceanic crust

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13
Q

Where can you find the youngest oceanic floor?

A

Near the mid-ocean ridges

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14
Q

Name the three types of plate boundaries.

A
  1. Convergent - move towards each other
  2. Divergent - move away from each other
  3. Transform - move sideways past each other
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15
Q

What is an example of a convergent boundary? divergent? transform?

A

Convergent - Overriding plate
Divergent - Mid-ocean Ridge
Transform - Shear/Strike-slip

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16
Q

What are Active Continental Margins?

A

found on the leading edge of the continent where it is crashing into an oceanic plate. Common site for tectonic activity.

17
Q

What are Passive Margins?

A

The transition between oceanic and continental lithosphere which is not an active plate margin.

18
Q

What is “Ridge Push”?

A

develops by the gravitational energy associated with the topographic elevation of the mid-ocean ridge.

19
Q

What is “Slab Pull”?

A

develops because the old oceanic lithosphere is more dense than the underlying asthenosphere, so it sinks.

20
Q

What two things does the Lithosphere consist of?

A

The crust and the uppermost mantle

21
Q

What is the Wadati-Benioff zone?

A

A planar zone of seismicity corresponding with the down-going slab in a subduction zone (660km depth)

22
Q

What is an accretionary prism?

A

a mass of sedimentary material scraped off a region of oceanic crust during subduction and piled up at the edge of the overriding plate.

23
Q

What produces a continental volcanic arc?

A

Subduction along the edge of a continent. Sediments on the downgoing slab are scraped off to form an accretionary prism.

24
Q

What produces an oceanic volcanic arc?

A

When two oceanic plates collide, the volcanic arc forms on the overriding plate.

25
Q

What is a triple junction?

A

A place where three plates intersect at a point.

26
Q

What are hot-spot volcanoes?

A

A consequence of mantle plumes. As a plate drifts over the hotspot, a chain of extinct volcanoes (a “hot-spot track”) forms.

27
Q

What is an example of a hot-spot track? What do they do?

A

The Hawaiian Islands. They provide clues to the

direction of plate movement.

28
Q

What is the process of rifting?

A

When continental lithosphere stretches and thins, the upper crust breaks by faulting. Upwelling asthenosphere initiates volcanism. Rifting may split a continent in two.

29
Q

Why doesn’t continental crust subduct?

A

It is too buoyant to subduct, so when two continents converge, rock undergoes compression and shearing, and a mountain range develops.

30
Q

Relative Plate Velocity

A

Describes motion of one plate relative to another.

31
Q

Absolute Plate Velocity

A

Describes motion compared to a fixed reference point in the mantle.

32
Q

The zone of the Earth that is divided into plates is the…

A

Lithosphere

33
Q

The observation that magnetic anomalies that constitute magnetozonesare found as far back in time as one can find appropriate rocks to measure indicates that:

A

The Earth has always had a convectingportion of its core over that time period

34
Q

How many times has the Earth’s ocean floor been

created and destroyed?

A

Atleast 25 times

Geology (21 decks)

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