Paleomagnetism Flashcards
At which geographic pole is the southern magnetic pole located?
The southern magnetic pole is currently located at the geographic north pole.
Geographic (True) north is located
On Earth’s spin axis
Current declination of earth’s north geomagnetic pole
NOT the same as true north.
Current difference is about 11.5 degrees.
What happens to your compass as you approach true magnetic north?
It becomes more erratic.
Where on earth is the magnetic inclination horizontal?
At the equator
Where on earth is the magnetic inclination horizontal?
At the geomagnetic poles
Where would a rock with this magnetic inclination have formed?
The northern hemisphere near the equator
Where would a rock with this magnetic inclination have formed?
At the northern hemisphere near the poles
How did this plate move?
In the southern hemisphere towards the equator.
How do magnetic inclinations change with location on earth?
Is the earth a permanent magnet?
No the interior is below the curie point of ferromagnetic materials.
geodynamo
The mechanism by which the earth shares it’s magnetic field
What sustains earth’s geodynamo?
It is sustained by a moving electric current caused by thermal convection in the liquid outer core.
Is earth’s actual magnetic field dipole or non dipole?
It is a combination of both, though it behaves mostly like a dipole.
If you remove the dipole firled, there are splotches of non-dipole fields
Evidence of earth’s magnetic field
Historic record of variable magnetic north wrt geographic north
Fossil traces of magnetic field in the past
Curie temperature
The temperature at which certain magnetic materials undergo a sharp change in their magnetic properties.
Thermal remnant magnetization
mineral grains fix their magnetic directions as the material cools.
What rocks show past magnetic inclinations?
Igneous rocks: Rocks cool and hold the geomagnetic field at the time of formation
Sedimentary rocks: Erosion of magnetic materials become suspended in water and become alligned at the time of settlng of the sediments
Apparent positions of magnetic poles in the past
not consistant with current poles.
True polar wanderer
Fixed continents.
Poles move relative to the continents
Recreation of paleopoles on separate continents should look similar.
Apparent polar wanders
Continental drift
continents move relative to the poles
Recreation of paleo paths is a unique path.
