Plate Tectonics

Question 1

What was Alfred Wegener’s theory?

Answer 1

in 1912, he had a theory that a single continent existed 300 million years ago and he named it Pangea

Question 2

What geographical evidence supports this?

Answer 2

south america and west africa fit together, glaciation deposits are formed in south america, antarctica and india, rock sequences in northern scotland and eastern canada

Question 3

What biological evidence supports this?

Answer 3

fossil brachiopods found in indian limestone are similar to ones found in australia, fossil remains found in south america and southern africa

Question 4

How has the theory developed?

Answer 4

the mid-Atlantic ridge was discovered and both sides of the ridge where shown to be spreading
this is because of alternating polarity of the rocks from the oceanic crust

Question 5

What is paleomagnetism?

Answer 5

this is when the lavas solidify and the iron particles which are in the rock provide a record of the earth’s polarity

Question 6

How often does the polarity reverse?

Answer 6

every 400,000 years and the oceanic crust gets older which distance away from the oceanic ridge

Question 7

What is gravitational sliding?

Answer 7

this is when the lithosphere thickens away from the mid ocean ridge and then the lithosphere/atmosphere boundary slopes away from the ridge