Plate Tectonics and the Ocean Floor Ch.2

Question 1

Crust composition

Answer 1

low-density, mainly silicate minerals

Question 2

mantle composition

Answer 2

mainly iron, and magnesium silicate minerals

Question 3

core

Answer 3

high-density, mainly iron and nickel

Question 4

Lithosphere

Answer 4

cool rigid shell, includes crust and upper mantle, about 100 km thick, forms tectonic plates

Question 5

Asthenosphere

Answer 5

• relatively hot
• flows with high viscosity
• base of lithosphere to about 700km deep

Question 6

Continenatl crust

Answer 6

granite (light coloured ingenous rock), density of 2.7 g/cubic cm, avg thickness of 35 km

Question 7

oceanic crust

Answer 7

basalt (dark igneous rock), density of 3, avg thickness of 8km

Question 8

Earthquake activity mirrors blank

Answer 8

tectonic plate boundaries

Question 9

most large earthquakes occur where?

Answer 9

at subduction zones

Question 10

Pangaea

Answer 10

one large continent existed 200 million years ago

Question 11

Panthalassa

Answer 11

one large ocean (200 million years ago)

Question 12

destructive margins (driving mechanism for plate motions)

Answer 12

at subduction zones at deep-sea trench

Question 13

constructive margins

Answer 13

at mid-ocean ridges at spreading ocean ridge

Question 14

litoshpere

Answer 14

rigid tectonic plates that float on ductile asthenosphere

Question 15

paleomagnetism

Answer 15

study of earth’s ancient magnetic field

Question 16

evidence for plate tectonics

Answer 16

• earth’s magnetic field
• polar wondering
• magnetic polarity reversals

Question 17

sea floor spreading evidence

Answer 17

• magnetic anomalies; regular pattern of north-south magnetism
• stripes were symmetrical about long underwater mountain range

Question 18

ocean crust formation

Answer 18

• ocean crust forms at mid-ocean ridge
• ocean crust moves away from mid-ocean ridge and cools and subsides
• and thickens (crustal underplating)

Question 19

divergent plate boundary

Answer 19

• plates move away from each other
• mid-ocean ridge; Rift Valley
• new ocean floor created

Question 20

convergent plate boundary

Answer 20

• plates move toward each other

- oceanic crust destroyed; ocean trench, volcanic arc

Question 21

transform plate boundary

Answer 21

-plates slide past each other
2 types
-oceanic transforma fault ; ocean floor only
-continrntal transform fault; cuts across continent

Question 22

volcanic hotspots

Answer 22

-a region of high volcanic activity not located at a tectonic plate boundary
-it is caused by upwelling of deep mantle plumes
-hotspots are intraplaye surface manifestiations of mantle plumes
-

Question 23

seamounts

Answer 23

rounded tops located between” islands”

Question 24

tablemounts or Guyot

Answer 24

flattended tops below the sea surface

Question 25

coral reef development

Answer 25

fringing reef ----> barrier reef -----> Atolls ------>

Question 26

fringing reefs

Answer 26

develop along margin of landmass

Question 27

barrier reef

Answer 27

seperated from landmass by lagoon

Question 28

Atolls

Answer 28

reef continues to grow after volcanoes are submerged, reef surounds a lagoon

Question 29

the oldest volcanoe

Answer 29

Maupiti

Question 30

Paleography

Answer 30

the study of ancient continents

Question 31

continental accrection

Answer 31

continental material added to edges of continents through plate motion

Question 32

Wilson cycle

Answer 32

life cycle of ocean basins; formation, growth, and destruction