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Physical Science
Question: How can magnetism of
rocks provide evidence of
continents moving?
Tuesday
• Connecting the rube to the physics
assignment
• Rube Check (today or tomorrow)
• Finish zones of earth questions
• Evidence for continental drift
New option for period 7,5
Create “The day in your life” Rube
List 32 actions that happen to you over the
course of a single 24-48 hour period
Each action is different from the other
actions in some significant way
New option continued
• Will have to connect your life to the
concepts discussed in class just like the
other groups and individuals
We have we already discussed
• Who was the first to propose that the continents
moved?
• What was so important about the extinct lizard
Mesosaurus?
• What is so important about finding rock evidence
that it was warm enough for forests in Antarctica
or that glaciers existed in hot areas of Africa?
What other evidence is there that
the continents have moved?
Age of ocean –vs- continental rocks
Physical shape of continents
Paleomagnetism
• Study of the Earth’s magnetic record
over time
• Hot rocks do not have a set
magnetic direction
• As it cools, the magnetic orientation
of is fixed
What is magnetic orientation?
Means the direction that the rock makes a
compass point as it passes over
Determining the magnetic
orientation of ocean rock
What has been discovered…
Discovered bands of rock with different magnetic
orientation as the ship moves away from ridge
• Evidence that the orientation reverses every
200,000 to several million years
• Matched bands with the same magnetic
orientation are found on both sides of a ridge
Orientation of rocks
around a ridge
Different colors represent rocks of
different geologic age
What is the best explanation for the
matched bands of rock?
• New ocean floor is being produced from
the ridge
• Older material material is pushed away
from ridge by newer material
• This in turn moves the continents apart
Who wants to act?
Mid ocean Ridges
• Are the place of creation of new plate material
• Boundary between plates
• As plates are created items on the plates are
moved farther away from the ridge
• Divergent boundary
Where do plates come together?
• Convergent boundary
• Subduction zones
• Most have a lot of volcanic and
earthquake activity associated with their
interaction
What happens at a subduction
zone?
• Density of material coming together
determines what happens
Ocean to continental crust
Continental to continental
Subduction zone - Japan
Subduction zone –The Himalayas