PMT - evidence of plate theories

Question 1

what is clear evidence of plate movement?

Answer 1

seafloor spreading

when tectonic plates diverge, resulting in the creation of new ocean floors

Question 2

who theorised sea floor spreading?

Answer 2

harry hess

Question 3

what does palaeomagnetism show?

Answer 3

new rock is formed and cools and the magnetism within the rocks align with the magnetic poles. the rocks make symmetrical bands of alternating magnetic polarity on each side

Question 4

in palaeomagnetism how often do the poles alternate?

Answer 4

400,000 years

Question 5

explain the process of sea floor spreading

Answer 5

• There are diverging plates moving apart from each other
• The plates are separating apart magma rises between the gap as its pushed up by convection currents and it cools and solidifies creating a new oceanic crust
• This rises and forms a new crust and pushes the older crust apart so both sides are symmetrical in age
• The new crust has iron minerals in its rocks which aligns with the earth’s magnetic field
• The earth’s magnetic field changes every 400,000 years so it’s in alternating directions
• The older crust subducts under the continental plate as its less dense in the process of subduction and is melted by the mantle