Explain what is required for a planet

1
To Instructor Students should be able to

• Explain what is required for a planets magnetic
  field to be generated by a dynamo.
• Describe the evidence that plates move, based on
  observations of magnetic patterns.
• Use paleomagnetic data to reconstruct past plate
  motion.
• Compare the Earths magnetic field with those of
  other planets and explain what the observations
  of those planets reveal about internal
  composition and structure.

The hotspot activity is directed toward achieving
the 2nd and 3rd of these goals. Prior
information should include generation of Earths
magnetic field, magnetic reversals, sea floor
spreading, and the development of remanent
magnetism, both in igneous and sedimentary
rocks/sediments.
See notes pages under subsequent slides for
information
2
Earths Magnetic Field - Inclination
Angle between Earthssurface and magneticfield
lines.
3
Earths Magnetic Field Inclination as a
function of latitude
At Vancouver Latitude 49 degrees
NorthInclination 67 degrees
4
Magnetic inclination evidence for WHERE rocks
formed
HOT SPOT VOLCANOESChains of volcanoes(and
single volcanoes)on the sea floor
5
The Mantle Plume Hypothesis
1. Hot spots form where narrow plumes rise by
convection from the core-mantle boundary
2. The plume locations are stationary in the
mantle
IF this is true, what would the evidence look
like?
6
Hotspot tracks(animation)
Fixed hotspot-moving plate model
Lithosphericplate motion
Resulting chainof volcanoes
Mantle plume
7
For instructor Have class do activity 1 before
continuing Next slide, discuss answers to
activity 1
8
What does the fixed hotspot moving plate
model imply about the direction of motion of the
Pacific Plate in the past?
gt45 MaN-ward
0-45 Ma NW-ward
Did this happen?
9
How
are hot spots?
FIXED
(and how could we tell?)
TESTING THE FIXED HOTSPOT MODEL WITH INCLINATION
10
How
are hot spots?
FIXED
What do you think happened?
Seamount Age (Ma) Inclination (º) Paleolatitude (º) Corals?
Detroit 78 Ma 60 No
Suiko 61 Ma 45 No
Nintoku 56 Ma 44 No
Koko 49 Ma 38 Yes
Hawaii 0 Ma 34 Yes
Data from Tarduno et al., Science, 2003
11
Seamount Age (Ma) Inclination (º) Paleolatitude (º) Corals?
Detroit 78 Ma 60 No
Suiko 61 Ma 45 No
Nintoku 56 Ma 44 No
Koko 49 Ma 38 Yes
Hawaii 0 Ma 34 Yes
42 27 26 22 19
12
Hotspot moving south
Hotspot mostly stationary
No Corals
Corals
? Moving plate moving hotspot!
13
Demo for after this activity (make the
Hawaii-Emperor seamount chain)

• Materials blank overhead and overhead pens
• You be the hotspot (pen). Get a volunteer to be
  the plate (overhead).
• Ask the volunteer to move the plate across the
  overhead projector to the NW (like the Pacific
  Plate)
• You be a fixed hotspot. Result linear chain
• You be a hotspot that moves south for a while,
  then becomes stationary. Result something very
  like the Hawaiian-Emperor Seamount Chain, with a
  sharp elbow