Chap 2 Plate Tectonics

Question 1

PANGEA:

Answer 1

Supercontinent that existed prior to tectonic plate movement.

Question 2

WEGNER’S EVIDENCE FOR CONTINENTAL DRIFT:

Answer 2

1. Observation of fit of continents
2. Locations of past glaciations
3. Distribution of equatorial belts (coal, sand and salt deposits in a belt due to similar climates)
4. Fossil distribution
5. Matching geographical units

Question 3

PALEOMAGNETISM:

Answer 3

Record of the ancient strength and orientation of Earth’s Magnetic Field

Question 4

How do ROCKS DEVELOP PALEOMAGNETISM

Answer 4

molten rock cools -> minerals crystallise -> during cooling the
minerals are affected by earth’s magnetic field -> strength and orientation of magnetic field preserved.

Question 5

POLAR WANDER:

Answer 5

The successive positions of dated paleopoles trace out a curving line that came to be known as an apparent polar-wander path

the magnetic field dipole of earth is 11⁰ off of earths geographical poles, this difference is called the magnetic declination

Question 6

POLAR WANDER: Hypothesis 1

Answer 6

(apparent polar wander path): earths
continents are fixed but the magnetic poles wander –
rejected as the study of palaeomagnetism didn’t show
and accurate belt of magnetic wander to prove this

Question 7

POLAR WANDER: Hypothesis 2

Answer 7

earths continents move but poles are
fixed – approved by
palaeomagnetism

Question 8

PALEOPOLE:

Answer 8

a magnetic pole of the earth as it was situated at a time in the distant past.

Question 9

SEA-FLOOR SPREADING

Answer 9

=continents drift apart because new
ocean floor forms between them by a process

Discovered by bathymetric maps that shows mid-ocean ridges (no sediment), submarine mountain ranges, trenches, seamount chains and fracture zones.

Question 10

Harry Hess’ hypothesis of spreading:

Answer 10

marine magnetic anomalies show sets of positive and negative
alternating bands on ocean floor that are symmetrical to each other which explains magnetic field reversals and sea-floor spreading from mid-ocean ridges.

Question 11

Subduction

Answer 11

continents move toward each other when the old
ocean floor between them sinks back down into the Earth’s interior

(The downgoing plate (the plate that sinks in the process of subduction)
must be composed of oceanic lithosphere.)

Question 12

Plate tectonics

Answer 12

a theory that Earth’s lithosphere
consists of ~20 distinct pieces (plates) that slowly move relative to one another

Question 13

PLATE BOUNDARIES:

Answer 13

when plate tectonics move, the internal part of the plate remains intact but the boundaries deform

Question 14

PLATE BOUNDARIES: Types

Answer 14

1. Divergent (constructive)
2. Convergent (destructive)
3. Transform

Question 15

Divergent (constructive) PLATE BOUNDARIES

Answer 15

= A plate boundary at which two
plates move apart from each other

mafic rock – forms pillow lavas. (mid ocean ridge)

Question 16

Convergent (destructive) PLATE BOUNDARIES

Answer 16

= A plate boundary at which two plates move toward each other so that one plate sinks
beneath the other

Subduction
occurs (oceanic-continental/oceanic)
or mountain ranges (continentalcontinental) (Andes mountains)

o Forms island arcs (2 oceanic
plates collide) or volcanic arcs (1 ocean plate and 1 continental)

o Wadati-benioff zone: belt of earthquakes on down-going plate

Question 17

Wadati-benioff zone

Answer 17

belt of earthquakes on down-going plate

Question 18

Transform: PLATE BOUNDARIES

Answer 18

plates slide past each
other (San Andreas Transform fault)

Question 19

TRIPLE JUNCTION:

Answer 19

Three plate boundaries
intersect (west coast of South America)

Question 20

HOT SPOT:

Answer 20

Places where a plume of hot mantle rock rises from just above the core-mantle boundary and causes anomalous volcanism at an isolated volcano

As a plate moves over the mantle plume, the
volcano moves off the hot spot and dies, and a new volcano forms over the hot spot. As a
result, hot spots spawn seamount chains

Mantle plume can lead to
eruptions when plate with volcanic/island arc
moves over it (Hawaii, Yellowstone)