The magma cools and forms a new crust, and iron-bearing minerals magnetize, then "freeze" in the direction of the prevailing magnetic field.
(iron-bearing minerals; magnetize then; ) (The magma cools and forms a new crust, and iron-bearing minerals magnetize, then; freeze; in the direction of the prevailing magnetic field)
iron-bearing minerals The magma cools and forms a new crust, and iron-bearing minerals magnetize, then
magnetize then freeze
in the direction of the prevailing magnetic field