Magnetic Stripes Flashcards
Earth’s magnetic field
invisible lines of force that extend from one magnetic pole to the other
Do the magnetic poles align with the geographic poles perfectly?
no
How do compass needles work?
get aligned with magnetic line of force and points to the magnetic poles/magnetic north
How do we know that we have a magnetic field?
can use it for navigation and some minerals are magnetitic
Definition of paleomagnetism
rocks record the strength and direction Earth’s magnetic field at the time the rocks formed
Example of the process of paleomagnetism using what type of rocks
iron-rich, volcanic, basalt, magnetite
Magnetic reversal
Earth’s magnetic field periodically reverses polarity, magnetic north poles will become south pole, vice versa
What do these rocks need to cool below for this process to begin, explain it pls
rocks in lava, once below, what happens?
Nonmagnetic in molten lava, but once below Curie point (585C for magnetite), iron grains become magnetized and align themselves in the direction of the present magnetic lines of force
Normal polarity
rocks with the same magnetism as the present magnetic field
reverse polarity
rocks with the opposite magnetism as the present magnetic field
What was used to create a magnetic time scale and what was used to create magnetic surveys?
radiometric dating
magnetometers
what were magnetometers originally used for and when?
to look for submarines
WW2
Why were oceanographers conducting magnetic surveys?
to make maps of seafloor topography and see variations in the strength of magn.field
What did Vine and Matthews discover?
high and low intensity strips supported seafloor spreading
High intensity stripes vs low intensity stripes (anomaly and polarity)
high intensity=positive anomaly and normal polarity
low intensity=negative anomaly and reverse polarity
What do the high and low intensity stripes do to Earth’s magnetic field?
high intensity: strengthen
low intensity: weakens
how are the stripes forming this symmetrical pattern?
magma solidifies and is magnetized with the present polarity, seafloor spreading causes it to widen, but reverse polarity seafloor will form in the middle of old strip (normal polarity), causing the same strip to be pulled in opp.directions
What was the drilling ship called of the Deep Sea Drilling Project?
Glomar Challenger
How did researchers on the Challenger date seafloor?
fossil remains of microorganisms in the sediment
Where are the youngest ocean floor found? oldest?
near ridge crest
far from ridge crest, near continents
what’s the age of the ocean floor?
180 million yrs old
How did the Hawaiian island chain form?
mantle plume rises, pressure drops, and partial melting occurs (hot spot.) As the Pacific plate moves over it, a hot-spot tack is built
Old Hawaiian island have ___ volcanoes? New?
inactive
active
