Chapter 3- Drifting Continents

Question 1

Plate tectonics

Answer 1

1960
- Harry Hess proposed seafloor spreading
-as continents drift apart, new ocean floor forms
-continents converge when ocean floor sinks into the interior
1968
Complete model was developed
Earth lithosphere broken into 20 plates that interact

Question 2

Alfred Wegner

Answer 2

• German meteorologist and polar explorer
• he hypothesized a former supercontinent, Pangaea
• the continents “fit”
• glacial deposits far from polar regions
• distribution of fossils

Question 3

Earths magnetic field

Answer 3

Flow in the liquid outer core creates the magnetic field

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Question 4

Magnetic poles

Answer 4

The magnetic pole intersects earths surface just like the geographic pile does

• magnetic N poor and magnetic s poles are located near geographic poles
• magnetic poles move constantly

Question 5

Knowledge of magnetic field

Answer 5

-geographic and magnetic poles are not parallel
-a compass points to magnetic N not geographic N
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Question 6

Declination

Answer 6

Different between geographic N and magnetic N
- depends on: 
Absolute position of the two poles 
Geographic north 
Magnetic north 
Longitude

Question 7

Inclination

Answer 7

Curved field lines cause a magnetic needle to tilt.
Normal or reverse polarity
Latitude

Question 8

Paleomagnetism

Answer 8

Rock magnetism can be measure in the laboratory

• iron (Fe) minerals in rocks preserve info on the magnetic field as rocks are formed.
• as rocks cools this is recorded
• can be in igneous and sedimentary rocks

Question 9

The oceans crust

Answer 9

Oceanic crust - thickest near the continents and thinnest at mid ocean ridges
- Mafic basalt and gabbro
No metamorphic rocks

Question 10

Sea-floor spreading

Answer 10

Sediments thickens from ridges

• earthquakes at mid-ocean ridges indicate cracking
• cracked crust splits apart
• molten rock rises into the cracked crust.
• contingent move closer together as sea floor is subducted

Question 11

Magnetic reversals

Answer 11

Polarity reversals explain magnetic anomaly stripes.

- the different magnetic polarities are recorded in sea spreading areas