Chapter 2 - Global Tectonics: Our Dynamic Planet & Chapter 20 - Earth Through Geologic Time

Question 1

Continental Drift

Answer 1

Theory by Alfred Wegener (1912); stated that continents plow slowly through solid rock of ocean floor; widely rejected

Question 2

Plate Tectonics

Answer 2

Ocean floor drifts as well as continents

Question 3

Isostasy

Answer 3

Continents/mountains stand high because they are thick and light ocean basins are topographically low because they are thin and dense

Question 4

Explanation for vertical motions of earth’s surface

Answer 4

Isostasy

Question 5

Explanation for horizontal motions of earth’s surface

Answer 5

Plate tectonics

Question 6

Geographic Edge of Oceans

Answer 6

Shoreline

Question 7

Geographic Edge of Tectonic Boundary

Answer 7

Where oceanic and continental crust meet

Question 8

Abyssal Floors

Answer 8

large, smooth areas of sea floor

Question 9

Mid-Ocean Ridge/Rift Valley

Answer 9

Form continuous feature greater than 60,000 km long. Mark where two oceanic plates spread apart and new lithosphere forms

Question 10

Passive Margins

Answer 10

Little earthquake and/or volcanic activity

Question 11

Continental Shelf

Answer 11

Shoreline to flooded margin

Question 12

Continental Slope

Answer 12

tectonic boundary at bottom of steeper

Question 13

Continental Rise

Answer 13

Gentle slope at bottom. Oceanic and continental lithosphere remain connected

Question 14

Active Margins

Answer 14

earthquakes and/or volcanoes common activity

Question 15

Mantle convection

Answer 15

circulation of hot rock from mantle to surface layers. Rock cools at surface, moves laterally, and sinks back down again.

Question 16

Geothermal Gradient

Answer 16

Increase in temperature with depth

Question 17

Adiabatic Expansion

Answer 17

mass of hot rock rising convectively from deep within earth cools off and expands.

Question 18

Convection

Answer 18

Driven mainly by subduction of cool, dense oceanic lithosphere sinking beneath edge of adjacent plate. Gravity then pulls into asthenosphere. Marked by deep ocean trench.

Question 19

Global Positioning System (GPS)

Answer 19

Proves: 1) points on earth’s surface drift at slow, steady rate. 2) Plate interiors are rigid

Question 20

Plate Boundaries/Margins

Answer 20

1) Divergent Margin (Type I)
2) Convergent Margin/Subduction Zone (Type II)
3) Convergent Margin/Collision Zone (Type III)
4) Transform Fault Margin (Type IV)

Question 21

Strike-slip faults

Answer 21

Known as transform faults when coincide with plate boundary; motion is entirely horizontal

Question 22

Thrust (and reverse) faults

Answer 22

Accommodate convergent motion between plates; motion is partly horizontal and partly vertical

Question 23

Normal faults

Answer 23

Accommodate divergent motion; motion also partly horizontal and partly vertical

Question 24

Divergent Margin (Type I)

Answer 24

Coincides w/mid-ocean ridge; magma forms in asthenosphere, rises to top of lithosphere, and emerges to form new oceanic crust; earthquakes are shallow and small; volcanic activity occurs along fissures; ridges rise 2+km above surrounding sea floor due to thermal expansion and isostasy

Question 25

Convergent Margin/Subduction Zone (Type II)

Answer 25

Subduction zone marked by volcanic island arc if overriding plate is oceanic, continental volcanic arc if continental; largest/ deepest earthquakes; Benioff zone extends up to 670 km

Question 26

Convergent Margin/Collision Zone (Type III)

Answer 26

Light, thick continental crust clogs subduction zone after oceanic portion of one plate has been completely subducted; continental plates crumple together to form collision zone; creates a mountain range

Question 27

Transform Fault Margin (Type IV)

Answer 27

Plates grind past each other horizontally along strike-slip faults; most link mid-ocean ridge segments

Question 28

Ridge push

Answer 28

Gravity induces lithosphere to slide down gentle slopes of mid-ocean ridge

Question 29

Slab pull

Answer 29

Cool, dense oceanic lithosphere sinks beneath edge of adjacent plate at subduction zones; gravity then pulls into asthenosphere at ocean trench

Question 30

Friction

Answer 30

Slab friction drags top, bottom and leading edge of descending lithosphere into subduction zone; plate friction drags elsewhere at base of plate